Underfloor Heating and Cooling

Underfloor cover:D3-2010 Legislation cover.qxd 13/12/2010 10:55 Page 1

A BSRIA Guide

www.bsria.co.uk

Underfloor Heating and Cooling

By Reginald Brown

BG 4/2011

ACKNOWLEDGEMENTS BSRIA would like to thank the Underfloor Heating Manufacturers Association (UHMA) for their support. The project was organised on behalf of UHMA by the following member companies: Rod Hickmott, Maincor (Fundraising) Mike Lamb, Warmafloor (Technical co-ordination). The project was undertaken by BSRIA with the assistance of a project steering group drawn from representatives of the following companies who provided BSRIA staff with technical assistance and supported the publication of this guide: Continental Underfloor Heating Danfoss Randall Ltd Emmeti Ltd Maincor Ltd Rehau Ltd Underfloor Warehouse Ltd Uponor Housing Solutions Ltd Warmafloor (GB) Ltd Wavin UK. Acknowledgement is also given to the following organisations for their assistance in providing technical information and commenting on draft publications: AECOM Hampshire County Council Hoare Lea National House-Building Council WSP. BSRIA would also like to thank John Sands who authored the original BSRIA publication AG 12/2001: Underfloor Heating Systems – The Designers Guide and provided initial input to this guide. This publication has been designed and produced by Ruth Radburn and Alex Goddard. BSRIA is grateful for the use of photographs and illustrations. The use of such photographs does not in any way imply endorsement of the products shown. Every opportunity has been taken to incorporate the views of the contributors, but final editorial control of this document rests with BSRIA.

This publication has been printed on Nine Lives Silk recycled paper. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher. ©BSRIA BG 4/2011

January 2011

ISBN 978 0 86022 690 1

Printed by ImageData Ltd

UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

CONTENTS 1 INTRODUCTION

1

1.1 Purpose of this guide 1.2 The format of this guide

1 1

2 PRINCIPLES 2.1 2.2 2.3 2.4

3

Thermal comfort Heat emitters Spatial temperature profile Benefits of underfloor heating

3 UNDERFLOOR TECHNOLOGY 3.1 3.2 3.3 3.4

Systems Floor structures Applications Underfloor cooling

27

4.1 Allocation of responsibilities 4.2 Provision of information 4.3 Design standards 4.4 Design criteria 4.5 Heat loss calculations 4.6 System sizing for heating 4.7 System sizing for cooling 4.8 System water flow rate 4.9 System water pressure drop 4.10 Layout 4.11 Control 4.12 Warranties and guarantees 4.13 Costs 5 DISTRIBUTION AND CONTROL Hydronic underfloor heating control Heating and cooling integration Electric underfloor systems Summary

6 ENERGY SOURCES 6.1 6.2 6.3 6.4 6.5 6.6 6.7

8 8 17 23 25

4 SYSTEM DESIGN

5.1 5.2 5.3 5.4

3 3 4 6

27 28 29 30 31 34 40 42 42 42 43 45 46 48 48 57 60 62 63

Conventional boilers Biomass boilers Heat pumps Combined heat and power plant Wind turbines Solar collectors Summary

63 64 66 73 74 74 76


CONTENTS 7 FLOOR FINISHES 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8

Surfaced concrete and screed Masonry finishes over concrete and screed Masonry finishes over floating or suspended floors Thermoplastic tubes Impact flooring Carpet and underlay Wood and laminate flooring Effect of floor finishes on thermal performance

8 INSTALLATION AND MAINTENANCE 8.1 8.2 8.3 8.4 8.5 8.6

Design issues Installation process Commissioning, balancing and start-up Handover Maintenance Thermographic surveys

REFERENCES

77 77 78 79 79 79 80 81 82 83 83 87 91 92 92 93 115

APPENDICES APPENDIX A: EXAMPLE CALCULATIONS

94

APPENDIX B: CHECKLISTS

98

APPENDIX C: 2010 BUILDING REGULATIONS

112

APPENDIX D: ESTIMATING COOLING CAPACITY

113


TABLES Table 1: Table 2: Table 3: Table 4: Table 5: Table 6: Table 7: Table 8: Table 9:

Table 10: Table 11: Table 12: Table 13: Table 14: Table 15: Table 16: Table 17: Table 18: Table 19: Table 20: Table 21: Table 22: Table 23: Table 24:

Comparison of underfloor heating with other systems 7 Comparison of underfloor heating pipes 12 Recommended insulation value below underfloor heating (from BS EN 1264-4:2009) 14 Types of insulation 15 Applicability of underfloor heating 23 Specific applications and benefits of underfloor heating and cooling 24 Applications not usually suitable for underfloor heating 25 Potential applications of underfloor cooling 26 Performance table showing heat outputs to BS EN 164 for 16mm OD PE-X/PE-RT underfloor heating pipes embedded within 75mm floor screed (50mm screed thickness above 2 39 pipe) – floor covering resistance of 0·00 m K/W Control elements associated with underfloor heating systems 52 Application of optimum start and night set-back 57 Typical properties of biomass fuel 65 Example variation of ground-source heat pump COP with temperature 67 Maximum extraction rates for buried ground coils 69 Recommended maximum length for different pipe sizes 70 Maximum extraction rates for close loop boreholes 70 Summary of potential low carbon heat sources for underfloor heating 76 Design criteria at an external temperature of 5ºC 94 U-values for various construction elements 94 Heat losses (excluding floor loss) 95 Required heat output values 95 Pipe spacing at 45°C 96 Pipe spacing at 45°C and 40°C 97 Water flow rate 97


FIGURES Figure 1: Ideal temperature profile Figure 2: Profile for underfloor heating Figure 3: Profile for radiators Figure 4: Profile for convector heating Figure 5: Typical screeded floor construction Figure 6: Typical floating floor construction Figure 7: Floating floor with spreader plates Figure 8: Pipe in insulation covered by screed Figure 9: Typical intermediate/suspended floor construction Figure 10: Pipe laid on insulation material set between joists Figure 11: Suspended floor system with quilt and spreader plates Figure 12: Heating pipe integrated within floor panel Figure 13: Underfloor heating for raised access floor system Figure 14: Annual hours exceeding an outdoor temperature Figure 15: Simplified product-specific sizing chart Figure 16: Simplified product-specific sizing chart for cooling Figure 17: Typical schematic for a domestic underfloor heating system Figure 18: Typical schematic for a commercial underfloor heating system Figure 19: Historical pipework circuit arrangement Figure 20: Modular heating manifolds Figure 21: Schematic of two-port manifold Figure 22: Typical pre-assembled two-port thermostatic manifolds with integral pump Figure 23: Underfloor heating circuit control Figure 24: Principle of weather-compensated flow temperature Figure 25: Underfloor heating circuit with weather compensation control Figure 26: Domestic central heating Figure 27: Passive cooling with ground-source heat pump (internal circulation pumps) Figure 28: Passive cooling with ground-source heat pump (external circulation pumps) Figure 29: Underfloor cooling for a boiler-fed system Figure 30: Cooling system controls Figure 31: Mains voltage electric floor heating Figure 32: An integrated biomass boiler and fuel delivery system Figure 33: Closed cycle vapour compression heat pump Figure 34: Horizontally laid coils Figure 35: Flat-plate solar collector Figure 36: Additional rug placed over carpet Figure 37: Example of a flushing bypass Figure 38: Colour thermographic image of an underfloor heating installation


5 5 5 5 18 19 19 20 20 21 21 22 23 25 37 41 44 44 49 50 50 51 53 54 54 56 58 58 59 60 61 64 67 69 75 82 90 93

INTRODUCTION

1

INTRODUCTION

1.1

PURPOSE OF THIS GUIDE

1

In 2001 BSRIA was asked by the underfloor heating industry to provide technical guides to help promote the understanding and application of underfloor heating. While underfloor heating systems that used the latest materials were seen as innovative and having enormous potential, there was little appreciation by building services designers of the technological and design issues. As a result BSRIA publications AG 12/2001: Underfloor Heating Systems – The Designers Guide and AG 13/2001: Underfloor Heating Systems- An Assessment Standard for Installations were published. It is now time to review this and this guide replaces the previous BSRIA publications. The objective of the guides was to familiarise building services designers with the basics of the technology, and to make them better able to select and apply the most suitable options. For other construction professionals such as architects, structural engineers, quantity surveyors and contractors the guides would help them appreciate the services issues and their relationship with other aspects of the building project. The guides would also be helpful for those professionals, such as facilities managers, who are not directly involved in the design and construction aspects of a project but are interested in the operational performance of underfloor heating, and non-technical people, such as clients and endusers who might be considering such systems. This revised guide reflects the advances in the technology, design methods and applications that have taken place in the last ten years, including the growth in cooling applications and the integration of renewable energy into many underfloor heating schemes. It should enable building services designers to familiarise themselves with the key issues surrounding the design of modern underfloor heating and cooling systems, assess whether those systems would be appropriate for their applications, and initiate the design process.

1.2

THE FORMAT OF THIS GUIDE

This guide is organised into the following sections: Principles - Discusses the essential principles of thermal comfort and the underlying reasons for differences in performance between conventional and underfloor heating solutions. Underfloor technology – Describes the typical components of underfloor heating and cooling systems. System design – Outlines the design process and explains where underfloor heating and cooling systems differ from conventional systems. Explains the calculation methods based on manufacturers’ information [1] produced in accordance with BS EN 1264 Part 3 (with worked examples) and introduces good design practice. Some of the technical issues are explored in more detail in later sections.


1

1

INTRODUCTION

Distribution and control – Examines controls and control strategies in more depth. Note that the schematics provided in this document are intended to explain the principles of operation discussed in the text. They do not necessarily show all the components (strainers, vents, pressurisation systems, expansion vessels, and safety valves) that are required for a complete system. Energy sources – Discusses the various sources of heat and cold that may be attached to the underfloor system including both conventional boiler and chiller plant and renewable heating and cooling options. Floor finishes – Compares different floor finishes in respect of their appropriateness for underfloor heating and cites the relevant standards. Installation and maintenance - Highlights good practice to help avoid installation problems on site. Provides useful guidance for other members of the professional team with respect to the interfaces between disciplines. The checklists in Appendix B are available as a download from the BSRIA website.

2


PRINCIPLES

2

PRINCIPLES

2.1

THERMAL COMFORT

2

The human body is a net producer of heat as a result of the metabolic processes that turn food into energy for physical activity. This heat is transferred to the surroundings by three processes: •

Radiation – the heat lost in radiation from the body, through clothing and exposed skin surfaces to cooler surroundings

•

Convection – the heat lost by convection from the body through clothing and exposed skin surfaces due to contact with the surrounding air, the temperature of which is considerably lower than the body

•

Evaporation – the heat lost from the body by evaporation from the skin, due to perspiration.

Lose too much heat and you feel cold. Lose too little heat and you feel hot. Humans adapt to the prevailing conditions where possible by varying their levels of clothing (which moderates convection and radiation losses) by physiological responses such as sweating or by modifying the local thermal environmental by heating or cooling. A good predictor of comfort in moderate thermal environments (without extremes of humidity) is the operative temperature. This is defined in BS [2] EN ISO 7730:2005 as the uniform temperature of an imaginary black enclosure in which an occupant would exchange the same amount of heat by radiation and convection as in the actual non-uniform environment. For air velocities less than 0·4 m/s and mean radiant temperatures less that 50°C the operative temperature is approximately equal to the average of the air and mean radiant temperatures. This means that an increase in mean radiant temperature can balance a decrease in air temperature. 2.2

HEAT EMITTERS

Heat emitters work by transferring heat from a distribution system into the building spaces by convection and radiation of heat. Increasing the proportion of radiant emission will tend to increase the mean radiant temperature of the space and allow the air temperature to be reduced for the same level of comfort, as explained above. As building heat losses are largely dependent on the difference in temperature between inside and outside air, this will tend to reduce the heat input necessary to maintain comfortable conditions in the space. The operating characteristics of different heat emitters are described below. Convective emitters

Predominantly convective emitters include radiators, natural convectors, fan convectors and unit heaters. Although conventional panel radiators do radiate heat, typically 70% of the heat is emitted by convection and only 30% by radiation, depending on the operating temperature and type. Radiators therefore rely on the natural convection of air in contact with a hot surface to draw the heat out of the emitter and carry it into the space. Radiators are often mounted below windows to counteract draughts caused by cold convection from the glass. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

3

2

PRINCIPLES

Radiative emitters

Predominantly radiative emitters include radiant strip/tube heaters, gas radiant tube heaters and underfloor heating. With the exception of underfloor heating, these are high or very high temperature systems, with surface temperatures ranging from 120°C for suspended radiant strip heaters to 500°C for a gas radiant tube. The high temperature promotes radiant emission, which is proportional to the absolute temperature of the radiant surface raised to the power four. Conventional underfloor heating consists of a plastic heating pipe or heating cable laid beneath a floor surface. The floor surface temperature is deliberately kept below 29°C. Despite this low surface temperature, heat is typically emitted in the proportions of 60% radiation and 40% convection, which are very similar proportions to a high temperature gas radiant tube. The explanation of this apparent paradox is that the floor has a very large surface area compared to a radiant tube or even a conventional radiator. For example, in a typical living room the area of underfloor heating surface could be 25% of the exposed surface area of the space compared to less than 5% for a panel radiator. Secondly, the surface temperature of the underfloor system is only slightly higher than the air above it. Consequently there is no large temperature difference to drive natural 2 convection. Of course, the specific heat output of the floor (W/m ) is very much less than for the surface of a high temperature heat emitter but the total output should still be sufficient to provide the required temperature in a reasonably well-insulated space. Underfloor heating therefore achieves many of the benefits of a radiant heating system but at a lower operating temperature than most convective systems. This concept is important in understanding why underfloor heating can reduce the energy required to heat a building. 2.3

SPATIAL TEMPERATURE PROFILE

The following diagrams illustrate the temperature profiles produced from various different types of heating systems. The occupied zone for a simple space is from the floor to two metres above the floor. The ideal case is shown in Figure 1 where the temperature reduces as it rises through the occupied zone, with the temperature level at its lowest at the ceiling. This is when people feel the most comfortable, in other words when their feet are a little warmer (by 1°C) than their heads. The underfloor heating profile shown in Figure 2 is the closest to the ideal profile shown in Figure 1, with minimal temperature rise between floor and ceiling. For very high spaces the underfloor profile moves even nearer to the ideal profile with the temperature reducing as height increases.

4


PRINCIPLES

Figure 1: Ideal temperature profile

2

Figure 2: Profile for underfloor heating

The radiator heating profile shown in Figure 3 has a higher temperature at ceiling level than at ground level, with a difference of approximately 2°C between the two positions. This is because warm air rises and becomes trapped under the ceiling. The temperature difference becomes even greater for the convector heating profile as shown in Figure 4: a difference of more than 5°C may be experienced. This effect is accentuated in tall spaces. Figure 3: Profile for radiators

Figure 4: Profile for convector heating

An underfloor cooling profile would be the mirror image of Figure 2 (lower floor temperature and higher ceiling temperature) but shifted to a slightly higher temperature range. This is also comfortable and avoids the issue of cold draughts and noise that can be induced by some forms of air-cooling.


5

2 2.4

PRINCIPLES

BENEFITS OF UNDERFLOOR HEATING

In summary, underfloor heating provides the following benefits for the indoor environment: •

Ideal temperature profile for comfort

•

Lower air temperature required to achieve comfort

•

Reduced ventilation heat losses and better energy efficiency

•

Absence of thermal stratification which also reduces heat losses

•

Low surface temperature which eliminates contact hazards

•

No thermally-induced air movement or convector fans to create draughts

•

Noiseless

•

Flexibility for fit-out and occupancy, as the heat emitters do not impinge into the space

•

Low risk of accidental or deliberate damage to the emitter

•

Low maintenance

•

Long life (50 years for underfloor pipework)

•

Low whole-life costs compared with other systems

•

Can also be used for cooling, in some cases at minimal additional cost.

Nevertheless, there are some circumstances where a different heating and/or cooling system might be more appropriate. That may be due to the thermal characteristics of the building, structural constraints or ultimate flexibility of the space. Once the pipes are embedded in the floor they can’t easily be moved. Selection criteria are discussed in Section 4.4. The practical advantages and disadvantages of underfloor heating compared to other heating technologies are listed in Table 1.

6


PRINCIPLES

2

Table 1: Comparison of underfloor heating with other systems System

Advantages

Disadvantages

Underfloor heating

Even temperature distribution

Generally slower response time (in solid floor applications only) compared to radiators

Reduced running costs Reduced convection currents Less obtrusive than radiators Maximum flexibility for furniture Inherently vandal-resistant

Radiator heating

Difficult to change underfloor pipe routes once installed Incompatible with certain types of floor coverings

Long life

Floor penetrations should be avoided, or very carefully planned. Damage to embedded pipework can be very disruptive and expensive to rectify

Fast response when required

Local hot spots

Easy and relatively cheap to replace

Risk of contact injuries (children & old persons) unless operated at low temperature or caged

Can be provided as towel rails in bathrooms

Prevention of corrosion and pinholing requires adequate water treatment Convection currents encourage the circulation of dust and mites Take up wall space reducing room usage flexibility Usually heating-only but can be combined with other systems Susceptible to surface damage and vandalism. May need to be repainted Air heating/cooling

Fast response Can be used to provide cooling and dehumidification Can be combined with ventilation (air handling units) or distributed systems (such as fan coils and variable refrigerant volume systems) Less obtrusive than radiators

High temperature radiant heating (for large spaces, factories and warehouses)

Very fast response High mean radiant temperature/low air temperature reduces ventilation losses Possible to retrofit. Can be reconfigured after installation. Suitable for localised heating

Distribution ductwork from central plant may impact on useful building volume Can be noisy unless carefully designed Can blow dust about De-stratification fans may be required in large spaces with industrial air heaters High maintenance costs (depending on the system) Minimum mounting height and separation distances from stored materials must be respected Gas supply and fluing for radiant tubes may restrict use of overhead space Quartz radiant systems have high primary energy consumption Limited fuel options (mainly gas or electricity)

The points made above are not necessarily the only ones that need to be considered when choosing a heating system. They need to be considered within the overall project context, and assessed accordingly.


7

warma floor:D3-2010 Legislation cover.qxd 04/01/2011 09:07 Page 1

Full Page Ad.v2:Layout 1 08/12/2010 10:31 Page 1

R

Underfloor Heating • Next day delivery nationwide • Prompt design and quote service • Fast expert advice when you need it • Widest range of installation methods • Technical advice for design solutions • Over 95% of our customers recommend us

0845 108 1204 [email protected] • www.continental-ufh.co.uk

3

UNDERFLOOR TECHNOLOGY

3


3.1

SYSTEMS

With conventional radiators, heat output is a function of the surface area and the mean temperature of the water flowing through it. Therefore, for a given radiator size, the output can be varied by changing the mean water temperature. The same principle applies to underfloor heating though the size of the emitter (in this case the floor) is so large that the mean water temperature can be much lower than that commonly used in radiators while still providing the required heat output. Wet underfloor heating systems work by passing low temperature hot water through pipework embedded in the floor structure. Heat is then radiated from the floor to warm the objects in the space. There is also a small component of heating by convection from the floor, which warms the air within the space. Downward losses are limited by a thick layer of insulation material underneath the heating pipes. In electric underfloor heating systems the heating pipes are replaced by an electric heating cable or heating mat. The rate of heat output from a wet system is determined by the following factors: •

Mean water temperature through the floor

•

Temperature of the space

•

Spacing and diameter of pipework

•

Thermal resistance of covering layers.

The mean water temperature and pipework spacing can be varied to provide the required space temperature, overcoming issues such as excessive heat loss, unfavourable floor coverings, or restricted emitter area. Similar systems from different manufacturers will tend to produce similar outputs for the same design parameters. In electric underfloor systems the cable or heating mat is laid out in a similar manner to underfloor heating pipes, though this is usually laid closer to the surface than for pipes, and the energy input modulated by a suitable controller. The temperature of the space used for detailed design calculations should be the required operative temperature. The air temperature (dry bulb) associated with underfloor heating in typical indoor environments such as offices, schools and hospitals will typically be 1°C below the operative temperature and the mean radiant temperature 1°C above the operative temperature. The following sections describe the major components of wet underfloor heating systems (the detailed design is covered in Section 3.3).

8



3

Heat sources

High-efficiency condensing boilers with modulating burners are ideal for wet underfloor heating as the low water temperatures allow the boiler to work in condensing mode for most of the time, thus maximising the energy efficiency benefits associated with an underfloor system. Non-condensing boilers can be used (where permitted by Building Regulations) but care must be taken to design the heating circuits to avoid sustained low return temperatures that could cause premature heat exchanger failure. Although the design return water temperature may be 35°C or 40ºC, the actual return temperature (from the floor) during an initial warm-up period may be much lower than this, possibly for 12 hours or more. Also, if a non-condensing boiler is supplying only underfloor heating, there may be a minimum temperature difference that needs to be respected to avoid excessive boiler cycling. A temperature difference of 5°C between flow and return may be ideal for the underfloor system but this could be too small for proper control of the boiler. This situation can be solved with a mixing circuit but designers should always check specific applications with the boiler manufacturer. In practice there are few situations where condensing boilers would not be specified for new stand-alone boiler system in single house or small commercial projects. The major exception is biomass boilers since these are not generally available as condensing versions. An alternative to a hot water boiler is the various forms of hydronic heat pump. These have ideal operating characteristics for efficient use with underfloor heating and can produce overall lower carbon emissions than a fossil fuel fired boiler. Some heat pumps systems may also be able to provide underfloor cooling. The use of heat pumps and other forms of renewable heat are discussed in Section 6.3. Other low carbon possibilities include linking the underfloor system to a combined heat and power plant or a district heating system where this is available. Electric underfloor systems may be appropriate in some situations where the hydronic systems would be impractical, provided that the building is highly insulated. The selection and characteristics of different heat sources are discussed in Section 6. Cool sources

Possibilities include natural cooling from the ground or mechanical cooling from a chiller or heat pump. The former uses a heat pump ground loop (usually via a plate heat-exchanger) to produce cold water at temperatures below 15°C for circulation through the underfloor system. This does not require operation of the heat pump itself and can be classed as “free cooling” though some pumping energy is required.


9

3


If a chiller or reversible heat pump is used to mechanically chill the water then a much lower temperature can be achieved. Although this will increase the specific cooling capacity of the underfloor system, the minimum circulation temperature must be limited to avoid surface condensation problems. Circulation

A circulating pump circulates heating or cooling water around the system. An underfloor heating system typically goes to a set-back condition at night rather than turning off altogether, so the pump may run for longer than in a conventional heating system. Pump energy consumption can be minimised by avoiding excessive pressure drops in the distribution and control system and employing variable-speed pump technology. Ideally, a single pump should be used to circulate water to manifolds and through the associated underfloor loops, though some systems may use a secondary pump and mixing valve attached to the underfloor manifold as discussed in Section 4. The latter arrangement tends to be used where the heat source and distribution system serves other heat emitters (radiators, fan coils, hot water cylinders etc) that require higher water temperatures and for systems that would otherwise be difficult to balance. Distribution pipework

The hot water from the heat source is conveyed to the individual manifolds via copper, steel or plastic pipework. The same pipework may also be used to distribute chilled water for cooling during summer. The optimum diameter of the distribution pipework depends on the flow rate, which in turn depends on the required heat transmission and temperature difference across the circuit. A larger temperature difference will reduce the flow rate, with the possibility of smaller pipework and pumps, but may reduce the overall energy efficiency of the system. Pipework insulation

In general, all heating and cooling distribution pipework should be insulated. This is mandatory where the pipework passes through unheated spaces. Insulation on chilled water pipework should be vapour sealed to avoid condensation. Particular attention should be paid to the insulation on and around control manifolds. In some situations it may be easier to mount the manifolds within a vapour sealed enclosure rather than to insulated and seal around individual control elements. The risk of condensation when using free cooling from the ground should be assessed on a case-by-case basis. Insulation may not always be necessary for plastic pipes carrying low temperature hot water through heated spaces to the floor, for example after the mixing valve on a weather-compensated circuit, as the uncontrolled losses should be rather small.

10


3


Flow and return manifolds

The manifolds (or headers) take low temperature hot water from the heat distribution system and distribute it through the underfloor circuits. There are separate manifolds for the flow and return connections. These manifolds are usually manufactured from brass or plastic (sometimes in modular form) and fitted with electric control valves and balancing valves for each circuit. From the manifolds, individual pipework loops are laid in the floor to provide the heating to the space, each loop constituting a separate controllable circuit. For larger rooms or spaces, more than one circuit may be required. The length of the manifold will depend on the number of circuits being provided. Manifolds can serve from two to twelve circuits, possibly grouped into several zones. Manifolds should be located so as to provide the best coverage for the various spaces and zones without having excessive runs to reach the areas being served. Several pairs of manifolds may therefore be required to provide the optimum pipework configuration even if some areas of the building have few circuits. Manifolds for domestic and light commercial applications vary in diameter from 20 mm nominal bore to 32 mm nominal bore. The length and diameter of the manifold depend on the number of connections and total flow rate. Underfloor heating pipe

Several different pipe systems have been developed specifically for underfloor heating applications based on the following materials: •

Cross-linked high-density polyethylene (PE-X) to BS 7291-3:2010 [4] or BS EN 15875-2:2003 with an oxygen barrier

•

Polybutylene (PB) to BS 7291-2:2010 or BS EN ISO 15876[6] 2:2003 with oxygen barrier

•

Aluminium/plastic multi-layer composite pipe.

[3]

[5]

All plastic heating pipes should incorporate an oxygen barrier. This barrier consists of one or more thin layers of a special polymer or, in the case of the composite pipe, aluminium foil incorporated into the pipe structure during manufacture. Reducing the ingress of oxygen reduces the rate of corrosion of the metallic parts of the system, such as boiler heat exchangers and pumps. The characteristics of each are summarised in Table 2. The practical difference in heating performance between these pipes, once installed, is negligible.


11

3


Table 2: Comparison of underfloor heating pipes Material

Description

Characteristics

Cross-linked high-density polyethylene (PE-X)

Manufactured from high-density polyethylene plastic and additives necessary to cross-link and stabilise the polymer for manufacture and subsequent conversion to pipes.

•

Very flexible

•

Oxygen barrier protected from damage

•

Good mechanical strength

•

Fifty year design life

•

Kinks during installation can be removed by applying gentle heat (not all types of PE-X).

Typically a multi-layer co-extrusion, with the oxygen barrier enclosed between polybutylene inner and outer layers to minimise the ingress of oxygen into the system through the pipe wall.

•

Very flexible

•

Oxygen barrier protected from damage

•

Good mechanical strength

•

Fifty year design life

Should conform to BS 7291 Part 2 or BS EN 15876[6].

•

Kinks formed in the pipe when bending cannot be completely straightened out.

A continuously overlapped or butt welded aluminium pipe forming an oxygen barrier enclosed between inner and outer layers of polyethylene or PE-X.

•

Very good mechanical strength

•

Can be 100% oxygen-proof

•

Low thermal expansion rate

•

Stays in shape once bent but can be reformed to new shape

Should conform to DIN 4726:2000[7].

•

Kinks formed in the pipe during bending cannot be completely straightened out

•

Slightly more expensive than other products.

[3]

Should conform to BS 7291 Part 3 or BS EN 15875[4].. Polybutylene (PB)

Metal/plastic multi-layer composite pipe

System designers should check the particular manufacturer’s literature for specifications and application guidance, and confirm that the pipe has a 50-year design life. In 1999, a BSRIA survey of the UK underfloor heating market showed PE-X accounting for approximately 60% of the pipework used in underfloor heating installations, with the other types detailed above providing the remaining 40%. Although this survey has not been repeated, informal feedback from manufacturers suggests that PE-X is still the predominant material. Cross-linked polyethylene (PE-X) comes in three forms, each using a different method of manufacture for achieving the cross-linking. The three types are: •

PE-Xa (peroxide cross-linked polyethylene)

•

PE-Xb (silane cross-linked polyethylene)

•

PE-Xc (radiation cross-linked polyethylene).

Each of these forms of PEX has its own physical characteristics and designers must satisfy themselves that the characteristics of the selected type are suitable for the system design being developed.

12



3

Other types of polyethylene pipe that may be encountered are described in BS EN ISO 22391-1:2009 Plastics Piping Systems for Hot and Cold [8] Water Installations. Polyethylene of Raised Temperature Resistance (PE-RT) and DIN 4724:2001 Plastic Piping Systems for Warm Water Floor Heating Systems and Radiator Pipe Connecting – Cross-Linked Polyethylene of Medium [9] Density (PE-MDX) . [10]

BS EN 1254-4:1998 also references polypropylene (PP), polyvinyl chloride (PVC-C) pipe as possible pipe materials (with references to relevant standards) but these are not generally used in the UK. Copper is no longer widely used for pipework in underfloor heating applications as it is difficult to install without having joints in the floor - a very undesirable situation in terms of preventing or repairing leaks. In practice most designers will select a proprietary underfloor heating solution consisting of matched components such as the pipe, the floor structure and insulation that are designed and tested to work together effectively in a predictable manner for a specific range of applications. In order to create a leak free system and maintain the oxygen barrier, it is important that only fittings recommended by the pipe manufacturer are used to connect the pipe. Temperature limits

A particular consideration for all systems is the maximum working temperature that may be attained under fault conditions. Although system may be designed for a maximum underfloor temperature of, say, 55°C for a screeded floor system (possibly higher for a suspended floor system), the pipework layout or control methodology may mean that it only takes a faulty valve or thermostat to allow higher temperature water to enter the underfloor circuit. If this condition continues for any length of time, it could not only damage the pipework and the floor covering but also invalidate the manufacturer’s or installer’s guarantee. A system designer should therefore: •

Assess the maximum underfloor temperature that could be reached under different fault conditions (for boiler controls and underfloor heating controls). In some cases this could be the maximum boiler flow temperature

•

Consider whether exposure to the maximum possible underfloor temperature could have a detrimental effect on the underfloor pipe, floor structure or covering

•

If necessary, use pipe with a higher temperature rating and/or consider additional safety controls to limit the maximum possible temperature at the flow manifold.

The Domestic Building Services Compliance Guide 2010 for the Building [11] Regulations recommends that all underfloor heating systems (whether of warm water or electrical types) connected to a high temperature heat supply should be fitted with the controls to ensure safe system operating temperatures, not more than 60°C. That may be achieved by providing a high limit thermostat on the heat supply or, for a mixed radiator and UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

13

3


underfloor system, a means of reducing the temperature to the underfloor system. Consideration should also be given to temperature limits for cooling applications in circumstances where the chilled water supply temperature could produce unwanted condensation effects on pipes, on the floor surface or in the floor structure. Water treatment

Although underfloor pipework is plastic, and therefore not subject to corrosion, other parts of the system such as boiler heat exchangers, pumps, control valves and possibly some of the distribution pipe will be metal. Conventional water treatment may therefore be required for the overall system. The water regime treatment (inhibitors, biocides and anti-freeze) should be compatible with all materials used in the system (metals, plastics and rubber). Insulation

Insulation is applied beneath the underfloor pipework to limit downward heat loss to no more than 10% of the heat supplied (as required in [12] BS EN 1264 Part 4 ) thus maximising the heat output into the room. This applies even where the underfloor system is installed above another occupied space. Table 3: Recommended insulation value below underfloor heating (from BS EN 1264-4:2009) Heat conduction resistance Rλ ins

Situation

(m2K)/W Heated room below or adjacent

0·75

Unheated or intermittently heated room below or adjacent, or directly on the ground (Note 1)

1·25

External temperature below or adjacent

External design temperature above 0°C

1·25

External design temperature 0°C to - 5°C

1·50

External design temperature -5°C to -15°C

2·00

Note 1: With ground water less than five metres below the supporting base this value should be increased

The Domestic Building Services Compliance Guide 2010 for the Building [11] Regulations introduces additional recommendations for exposed ground floors, as follows verbatim: “Ground floors on earth, or suspended floors in contact with outside air, should be insulated to limit downward heat loss to not more than 2 10 W/m resulting from the thermal resistance of the applied floor finish. When the heat output is not known, but the floor finish is specified, the extra amount of system thermal insulation may be calculated using the sum of the thermal resistance of the floor finish and the thermal resistance 14



3

of the underlying heated layer all multiplied by a factor of 10. Supplementary floor heating system thermal insulation may be supplied independently or added to the statutory insulation requirement.” The Domestic Building Services Compliance Guide 2010 for the Building [11] Regulations also recommends that electric underfloor systems applied to intermediate floors should either comply with the above or have a separating layer of system thermal insulation where the minimum 2 thermal resistance Rλ is not less than 0·5 (m K)/W. The thermal characteristics of the common types of floor insulation material are listed below. Table 4: Types of insulation Insulation type

Thermal conductivity W/m2K

Expanded polystyrene

0·033 - 0·037

Extruded polystyrene

0·024 - 0·027

Vacuum extruded polystyrene

0·026 - 0·027

Polyisocyanurate foam

0·020

Rockwool

0·037

Urethane

0·022

Polyurethane and polystyrene come in a number of density grades, each providing different levels of mechanical strength and resistance to compression. For domestic applications, standard flooring insulation grades or purpose-designed preformed products can be used, as the overall loads are likely to be relatively low. Heavier grades of insulation may be required in commercial and industrial situations, possibly in conjunction with reinforcement of the overlying layer. This should be discussed between the structural engineer and architect. The compression strength of expanded polystyrene can be less than for polyurethane products while the thickness is likely to be greater to achieve the same insulation effect. While high-density polystyrene is the minimum grade that should be used in any application, advice should be sought from the insulation manufacturer on the appropriate grade to use for each particular scheme. Factors to be considered include compression strength, thermal conductivity and moisture resistance. Expanded polystyrene also requires a vapour barrier between it and the screed as its structure is porous and can absorb moisture. This vapour barrier must be completely sealed to prevent screed penetrating and getting below the insulation. Pipe fixings must be carefully selected to ensure that they do not endanger the integrity of the vapour barrier when installed. It is very important to provide edge insulation around the perimeter of the area where underfloor heating is installed to avoid loss of heat into the building structure. Edge insulation also allows for expansion of the slab and helps to reduce structural-borne vibration. Additional expansion joints may be needed within the heated floor area if this is large.


15

3


Screed

Screed is the material used to embed the heating pipe or cable for solid floors and some suspended floors. The two main types of screed are sand and cement screed and anhydrite (calcium sulphate) screed. The latter is often used as a pourable self-levelling screed. Various admixtures are used in proprietary screed formulations, particularly to improve curing and resistance to cracking. The use of screed is further discusses in Section 7 and in the Co[13] Construct guide IEP 11/2003: Screeds with Underfloor Heating . Spreader plates

Spreader plates, also known as diffusion plates, are used in floating floors to spread heat across the under surface of the flooring material. Further details of floor construction are covered in Section 3.2. Electric underfloor heating

Electric underfloor heating is widely used for areas where a traditional wet system would be inappropriate on the grounds of cost or accessibility to boiler plant. There are two basic forms of electric underfloor heating: •

Cable based – A heating cable can be laid in the floor screed in a similar way to pipe, or on the surface of the screed under tiles. The cable is then wired into a suitable power circuit via a control box and isolator. Control can be by individual room thermostat and/or by timer

•

Mat-type – The single-ended cable is bonded to a mat or mesh, which is produced in the form of a roll. The roll is typically around 500 mm wide, and is laid out over the screed. Connections and controls are similar to those for a cable system.

Typical electrical outputs are around 12 - 20 W/m (per linear metre) for 2 floor laid cable systems, and 100 – 150 W/m format. A recent development in electric underfloor heating is carbon film. This comes in the form of a roll of plastic carrier material containing transverse strips of carbon film connected between conductors along each edge. It is mainly targeted at the do-it-yourself retrofit market and specifically designed to produce an even low temperature heat distribution underneath wood and laminate floors. The heat output is similar to that of underfloor heating mat. It is recommended that an underfloor temperature sensor be fitted in each zone in addition to the air temperature sensor (see also Section 5.3). Mains voltage underfloor heating systems must be tested and commissioned by a qualified electrician with particular attention to earth bonding arrangements. Satisfactory test certificates must be issued before use. Not all mains systems are suitable for installation in wet areas. Low voltage systems are sometimes used in bathrooms.

16



3.2

FLOOR STRUCTURES

3

Underfloor heating and cooling can be used on any of the typical floor constructions used in UK buildings. The three most common types of floor construction in housing are solid ground floor, floating floor and timber/intermediate floor. Floor construction for commercial buildings includes screeded hollow core concrete planks, cast in situ floors and composite constructions. Special solutions exist for underfloor heating and cooling of raised access floors. Solid ground floor

Although there are a number of subtle variations employed by different manufacturers to suit their particular materials and systems in the installation of underfloor heating, the basic philosophy is the same for all solid floor types. A layer of insulation is laid on top of the concrete slab to minimise ground losses and ensure that most of the heat (greater than 90%) travels upwards. This also acts as a levelling layer to which the pipework will be fixed. The insulation layer must be protected by a waterproof membrane. This will prevent moisture from the screed penetrating the insulation and reducing its effectiveness. The underfloor heating pipework is then laid onto the top of the insulation and fixed by a number of methods prior to screeding. Three common methods are: •

A rail (which incorporates profiled securing clips at set distances along its length) is fixed above the insulation, with the pipe laid out in the required pattern and held in place by forcing it into the rail clips (as shown in Figure 5)

•

The pipe is laid out in the desired pattern and then staples pushed over the pipe into the insulation to hold in place. This is very common for commercial installations

•

The pipe is tied to a steel mesh to be embedded within the screed (or concrete). This provides flexibility in installation (spacing and depth), but can take longer to install.


17

3


Figure 5: Typical screeded floor construction

All these methods can be used individually, or in any combination to suit a particular application as required. A layer of screed is then laid on top of the pipework to form the heat transfer medium, and to level and strengthen the floor ready for the final floor finish of carpet, tiles or stone. With this type of flooring, edge insulation is required to avoid cold bridging with the structure, except on timber-frame buildings, which permits heat to be drawn away from the floor and reduces the efficiency of the system. Allowance must also be made for expansion joints within the floor slabs. With a screeded floor system, it is essential that the screed is allowed time to dry out thoroughly, and that such time is allowed for this within the construction process (typically 28 days for a sand and cement screed). Failure of screeds due to insufficient moisture control can result in very expensive and disruptive remedial works being required. Further information on the use of screeds is contained in Section 7.1. The use of mesh to reduce shrinkage may also be required and any requirements for screed thickness by the warranting authority must also be considered. Similar construction details, with a lesser thickness of insulation, are applied to screeded floor slabs in the upper floors of apartment blocks and commercial buildings.

18



3

Floating floor

Floating floor installations can (see Figure 6 and Figure 7) be achieved by laying a pre-formed high-density polystyrene profiled panel on top of the prepared base, either an existing flooring system or a new construction. The pipework is laid into the pre-formed profile, with or without metal spreader plates to distribute the heat over a wider area. The floor decking – generally chipboard, finished timber or laminate – is laid on top. Although the decking sections are glued together, they are not fixed to the insulation but left to float on top of it. If carpet is to be used, this is then laid onto the chipboard decking. Figure 6: Typical floating floor construction

Figure 7: Floating floor with spreader plates

Source: Warmafloor


19

3


Alternatively, the insulation material and pipe can be covered with a 25 mm layer of screed to diffuse the heat and increase the thermal mass (see Figure 8). Figure 8: Pipe in insulation covered by screed

Source: Based on information from Thermoboard

Timber intermediate or suspended floor

The heating pipe can either be installed between the joists or on top of them. One method involves fitting insulation between the floor joists at approximately 25 mm below the top of the joists. The pipework is then laid on top of the insulation and the space between the top of the insulation and the top of the joists filled with a sand and cement mix as detailed in Figure 9. Figure 9: Typical intermediate/suspended floor construction

20



3

Alternatively, the pipe can be laid on insulation material set between the joists and topped with a spreader plate system (see Figure 10). Figure 10: Pipe laid on insulation material set between joists

Source: Based on information from Rehau

Other methods include installing insulation between joists and then battening perpendicularly over the top of the floor joists and laying the pipework between the battens in spreader plates (see Figure 11). The advantage of this method is that the pipes run wholly over the tops of the joists without notching, and no screed is involved. The disadvantage is that there is some loss in room height, though less than for a floating-floor system. Figure 11: Suspended floor system with quilt and spreader plates

Source: Warmafloor


21

3


Some companies simplify various aspects of the installation process by replacing traditional insulation with a very high thermal value quilt that can be laid over or between the joists, providing insulation panels with preformed channels or integrating the pipework inside a structural flooring panel (see Figure 12). These developments are claimed to save time on installation and provide improved comfort and/or sound reduction. Figure 12: Heating pipe integrated within floor panel

Source: Based on information from Thermoboard

In all types of wood-based flooring systems, the designer must be aware of the lower heat output relative to concrete floors. Whereas an underfloor heating system installed on a typical solid floor construction 2, may produce an output of 100 W/m for some floating floors, or suspended timber floors and intermediate timber floors, this will normally 2 2 drop to around 70 W/m . It may fall to nearer 50 W/m , where carpet is used as the final floor finish. This must be borne in mind by the designer, and discussed with the other members of the design team and the client at the appropriate stage of the project. Commercial and industrial floors

Where a heavy-duty surface is required the underfloor heating can be embedded directly in power-floated concrete that is subsequently ground to a flat finish and coated. This is similar in principle to replacing the screed with a layer of concrete, reinforced with steel mesh. The underfloor heating tube can be tied to the steel mesh prior to pouring the concrete. A layer of insulation must still be incorporated in the floor slab below the heating layer to limit the downward heat losses. The concrete over-layer can be made sufficiently thick so that the heating pipes are out of range of normal floor fixings (for racking etc). This will increase the thermal mass of the heated floor and so is most suitable for buildings that need continuous heating, though possibly only to a relatively low temperature. Raised access flooring

Underfloor heating and cooling may at first sight seem incompatible with the raised access flooring found in many offices but there are specialised products for this application as shown in Figure 13. These use spreader

22



3

plates mounted between the floor tile pedestals to transfer heat to or from the floor tiles. Figure 13: Underfloor heating for raised access floor system

Source: Based on information from Warmafloor

3.3

APPLICATIONS

The intrinsic characteristics of underfloor heating and cooling, including energy efficiency, economy and excellent thermal comfort make it the ideal choice for most but not all applications. Limiting factors are the: •

specific thermal output

•

speed of response

•

system cannot easily be re-configured once installed.

Table 5 indicates some limits to the applicability of underfloor heating while Table 6 identifies some of the specific applications and corresponding benefits of underfloor heating. Table 7 lists those applications not usually considered appropriate for underfloor heating or whether further consideration may be needed before specification. Most of the applications considered suitable for underfloor heating will also be suitable for underfloor cooling if required. Table 5: Applicability of underfloor heating Suitable for

Not suitable for

Buildings or areas that are used continually or frequently

Buildings or areas that are used very intermittently or infrequently

Buildings or areas with relatively low heat losses

Buildings or areas with high heat losses, particularly when due to high ventilation rates

All ceiling heights including atria

Buildings where unpredictable re-zoning may occur

Use with all heat sources

Areas where the floor is largely obscured by permanent fixtures and fittings


23

3


Table 6: Specific applications and benefits of underfloor heating and cooling Building type

Reason why suitable

Most housing

Absence of radiators provides flexibility for furnishing Slow response may be an issue if heating is occasionally required outside the main heating season

Schools

Maximum flexibility in the use of the space No risk of injury from radiators with high temperatures or sharp corners Underfloor systems are inherently vandal-resistant Suitable for large volume internal spaces such as assembly halls and gyms

Nurseries and playgroups

Warmer floors for young children No need to place protective enclosures around radiators Reduced bacterial growth in floor finishes from lower humidity

Atriums

Good comfort within the occupied zone (0-2 m above the floor) Reduced stratification compared to other forms of heating reduces energy losses Areas with extensive horizontal glazing may require supplementary heating to achieve sedentary comfort levels in peripheral areas with high heat loss

Healthcare premises, such as hospitals, day care centres, sheltered housing

Uniform thermal conditions No need to place protective enclosures around radiators or problems of cleaning behind radiators Reduced bacterial growth in floor finishes from lower humidity

Offices

Full utilisation of floor space Suitable for large open areas which are, high volume and internal Care needs to be taken in the application of the system on external zones, for example existing buildings with large solar gains, and in conference and meeting room facilities with varying internal loads

Museums and galleries

No local hot spots that may cause damage to exhibits Lower air temperatures probably less harmful to exhibits Reduced convection currents reduce the spread of dust

Libraries

Lower air temperatures probably less harmful to books Reduced convection currents reduce the spread of dust Care needs to be taken when fixing shelving to floors to avoid damaging underfloor pipework

Leisure centres and health clubs (particularly around swimming pool perimeters)

Increased safety due to dry floors Uniformity of conditions Underfloor systems are protected from damage

Changing rooms

Increased safety due to dry floors Reduced bacterial growth in floor finishes Maximum use of wall space Warmer floors appropriate for bare feet

Car showrooms

Good solution for background heating of areas with a large proportion of full height glazing Care must be taken to ensure the loadings of parked vehicles can be properly accommodated

Police stations and prisons

System is hidden and resistant to damage. Absence of radiators improves safety. Flexible use of space

Churches

Good comfort within the occupied zone Reduced stratification compared to other forms of heating reduces energy losses May not be suitable for very intermittently-used churches, due to long warm-up period

Warehouses

No radiators or other heat emitters impeding access Ideal for constant low temperature background heating Care needs to be taken with fixing shelving and racking to floors to avoid damaging pipes Temperature-sensitive products should not be stored directly on the floor Underfloor heating may not be suitable for areas with frequently used loading doors and high air change rates

Horticultural buildings

24

Ideal for low level background heating and frost protection



3

Table 7: Applications not usually suitable for underfloor heating Building type

Reason why unsuitable

Community halls, intermittently used

Community halls may be used only once or twice a week and then possibly for a short time. Underfloor heating may not be able to bring the room up to temperature quickly from cold and permanently running set-back conditions may prove expensive

Churches etc with infrequent use

Some churches or chapels only have services one day per month. In these cases, an underfloor heating system need a warm up period of several days and the heat stored in the floor will be re-emitted after the event when the building is unoccupied

Any lightweight building with high ventilation rates and poor insulation

There may be problems in achieving sufficient heat output from the floor to compensate for excessive heat losses

Warehouse areas with high floor coverage

Underfloor heating is suitable for many warehouses but should not be used where significant amounts of material or pallets are stacked directly on the floor. Although there is usually no risk to non-perishable material stacked above an underfloor system, obscuration of the floor surface will reduce the overall heat output

Areas with extensive fullheight glazing

The radiant cooling effect in winter may impose too high a heating load to achieve sedentary comfort conditions for near-window areas. Underfloor heating may still be acceptable for certain applications such as car showrooms, as mentioned above

3.4

UNDERFLOOR COOLING

A temperature of up to 25°C is generally considered acceptable in homes and workplaces during the summer. The UK has a temperate climate where the hourly outside air temperatures in rural areas typically exceed 25°C for less than 1% of the time (an example of actual weather data is shown in Figure 14). Therefore, unless there are significant heat gains, excessive indoor temperatures can be avoided for most of the time simply by increasing the ventilation rate. Figure 14: Annual hours exceeding an outdoor temperature


25

3


Where there are significant heat gains such as excessive solar radiation, high levels of lighting, IT equipment, or high density occupation, and particularly in city areas where the urban heat island effect raises average air temperatures, then cooling may be required throughout the summer period and in some cases through much of the year. Underfloor cooling can, if required, be applied in almost all situations where underfloor heating would be suitable. However, for areas with high heat gains, underfloor cooling alone may not be able to satisfy the total cooling requirement. In these situations underfloor cooling may be used in conjunction with conventional cooling equipment, such as air handling units and chilled beams. These combination systems should provide improved comfort relative to air-only cooling as the underfloor cooling will lower the radiant temperature in the space, improve the temperature distribution and reduce fan noise. Underfloor cooling may also provide an element of thermal storage that allows for more efficient utilisation of the cooling plant. Some potential examples of underfloor cooling are shown in Table 8. Table 8: Potential applications of underfloor cooling Heating only

Possible underfloor cooling

Conventional cooling

Rural/suburban housing Rural/suburban schools Community buildings Churches Warehouses

City apartments General offices City schools Suburban hospitals (general areas) Local shops Local restaurants and cafes Leisure centres Factories

High density offices Department stores Food retail Theatres and cinemas City hospitals City restaurants City hotels

Active and passive underfloor cooling

Passive underfloor cooling is where system water is circulated through a heat exchanger linked to the ground loop of a ground-source heat pump. This can provide a circulation temperature of 15°C – 18°C. The heat pump is not operated so the only energy requirement is for pumping. Active underfloor cooling is where system water is provided by an aircooled chiller or reversible ground-source heat pump. Lower circulation temperatures (less than 10°C) are available but underfloor temperatures will be constrained by the need to avoid the risk of condensation. 2 Cooling loads of 50 W/m are possible. One benefit of using underfloor cooling with ground-source heat pumps, whether active or passive, is that the dissipated heat helps to recharge the ground in preparation for the heating season. Therefore such a system will have improved long-term heating performance relative to a heatingonly system. For guidance on the integration of heating and cooling systems and the control of cooling systems see Section 5.2.

26


SYSTEM DESIGN

4

SYSTEM DESIGN

4.1

ALLOCATION OF RESPONSIBILITIES

4

To produce an effective system design, all necessary information needs to be gathered and the calculations progressed in a suitable sequence to arrive at an appropriate solution. The intention of this publication is to make the reader aware of the issues involved and be able to carry out the project design task confidently and communicate with the underfloor heating specialist effectively. Generally, the project designer (depending on the project this may be the services designer, design team, consultant or architect) will be responsible for calculating the design heating and cooling loads for each zone together with the arrangement of central plant, distribution pipework and control strategy necessary to satisfy these loads within the initial scheme design. An underfloor heating specialist (supplier or installer) will then be contracted to produce the final design of the underfloor installation from the manifold onwards, and the sub-schedule of works. In single house and other small applications, the heating distribution design may be undertaken by an underfloor heating specialist. However, the provision of heat loss calculations is always the responsibility of the project designer, not the underfloor heating specialist. In all projects the project designer must agree the scope of design responsibility with the underfloor heating specialist and carefully check and clarify what the underfloor heating specialist does or does not include within their package, such as: •

Design assumptions and calculations

•

Underfloor installation drawings

•

Supplying and fitting insulation

•

Supplying and fitting underfloor pipe

•

Supplying and fitting manifolds

•

The pressure test

•

Protection of part-finished works

•

Supply and laying of the screed

•

Supply and fitting of controls

•

Finishing of the floor surface

•

Flushing and treatment of system water

•

Connection of manifolds to the heating and cooling system

•

Commissioning the underfloor system

•

Provision of warranties

•

Attendance at interface meetings with other systems/contractors

•

Management supervision during works

•

Performance testing.


27

4

SYSTEM DESIGN

In turn, the underfloor heating specialist must make the project designer aware of what they expect to be provided during design and installation works. This would cover copies of all relevant documentation including client specifications, design calculations and assumptions, building plans, and system schematics as discussed below. Other issues could include: •

Provision of temporary services (such as water and electricity) during works

•

Quarantine of work areas during underfloor pipe laying and covering

•

Access for plant and equipment

•

Provision of temporary accommodation for operatives and secure storage facilities for materials and equipment

•

Format of drawings and schematics.

Any areas where responsibility is not explicitly allocated should be discussed between the underfloor heating specialist and the design team at the earliest opportunity and the decision documented in the contract. If it is not written down it cannot be assumed it will be done. 4.2

28

PROVISION OF INFORMATION

Information provided to the underfloor heating specialist by the project designer will usually include: •

Building plans including the general layout, heating/cooling zones, structure and services

•

Client specification for heating/cooling performance in each zone

•

Design assumptions and heating/cooling load calculation for each zone

•

Operational assumptions including occupancy patterns

•

Specification of controls and control strategy

•

Specification and location of proposed floor coverings

•

Plans showing the arrangement of floor standing fixtures and fittings, such as fixed furniture, floor standing cupboards and large appliances

•

Plans showing areas that may need special consideration, such as those with large areas of glazing and entrance lobbies

•

Specification of central plant

•

Specification of the heating and cooling distribution including limiting temperatures and flow rates

•

Schematics of the heating and cooling distribution

•

Project schedule for the overall construction

•

Health and safety policy documents

•

Site working hours and limitations

•

Contact details for key personnel.


SYSTEM DESIGN

4.3

DESIGN STANDARDS

4

The standards relevant to the design of underfloor heating and cooling systems, particularly BS EN 1264, have recently been rationalised and revised to reflect commercial practice in underfloor heating. The titles have also changed to reflect the significance of underfloor cooling. Most of the material of relevance to the designer is now in BS EN 1264 Part 3 and Part 4 but should also be reflected in manufacturers’ application guidance. The current parts of BS EN 1264 are as follows: •

BS EN 1264-1: 1998: Floor Heating - Systems and Components. [14] Definitions and Symbols . Part 1 is the only part that remains from the original standard

•

BS EN 1264-2:2008: Water Based Surface Embedded Heating and Cooling Systems. Floor Heating. Prove Methods for the Determination of the [15] Thermal Output using Calculation and Test Method . Part 2 deals with the calculation and/or testing of the performance of underfloor heating systems. It is mainly used by manufacturers to produce product specific data

•

BS EN 1264-3:2009 Water Based Surface Embedded Heating and [1] Cooling Systems. Dimensioning . Part 3 describes how designers should utilise the results coming from Part 2 and Part 5 of the standard to design actual systems. This is the basis of the design methodology described in this guide

•

BS EN 1264-4:2009 Water Based Surface Embedded Heating and [12] Cooling Systems. Installation . Part 4 covers miscellaneous issues associated with the installation including the use of materials, floor construction and bringing into use

•

BS EN 1264-5:2008 Water Based Surface Embedded Heating and Cooling Systems. Heating and Cooling Surfaces Embedded in Floors, [16] Ceilings and Walls. Determination of the Thermal Output . Part 5 details how manufacturers should express the performance of underfloor heating and cooling systems in a consistent manner to simplify product comparison.

Note that BS EN 15377-1:2008 Heating Systems in Buildings. Design of Embedded Water Based Surface Heating and Cooling Systems - Determination [17] of the Design Heating and Cooling Capacity may still be relevant to manufacturers for calculation of heat output for floating floor constructions, but BS EN 15377-2:2008 Heating Systems in Buildings. Design of Embedded Water Based Surface Heating and Cooling System. Design, Dimensioning and Installation has been withdrawn in favour of BS EN 1264-3:2009 Water Based Surface Embedded Heating and Cooling Systems. [15] Dimensioning .


29

4 4.4

SYSTEM DESIGN

DESIGN CRITERIA

Design temperatures

The internal design temperature should be expressed in terms of the operative temperature for the reasons outlined in Section 2.1. If not already specified by the client, then suggested design temperatures for different applications can be found from a number of sources such as: •

BS EN 12831:2003 Heating Systems in Buildings. Method for [18] Calculation of the Design Heat Load. Annex A

•

CIBSE Guide A. Environmental Design

•

British Council for Offices Guide to Specifications 2009

[19] [20]

.

The outdoor design temperature appropriate to locations in the UK can also be found in CIBSE Guide A. Floor surface temperatures

The temperature of the floor surface must be sufficient to provide the required heat transfer into the space but not so high as to cause discomfort to the occupants. The guidance document BS EN 1264-3 suggests that the ‘physiologically-agreed’ (sic) maximum floor surface temperature is 9ºC above the room temperature for residence areas, including areas of normal use and regular occupancy. This results in a maximum floor surface temperature of 29ºC in normally occupied areas with a room temperature of 20ºC, and 33ºC in bath and shower rooms with a room temperature of 24ºC. For peripheral areas where people would not normally be seated, the maximum floor surface temperature could be 15ºC above the room temperature, to a maximum of 35ºC. These higher surface temperatures are sometimes desirable in areas adjacent to external walls or windows to offset the local drop in mean radiant temperature. The increase in surface temperature should be achieved mainly by decreasing the spacing between pipes rather than by raising the flow temperature. It is vital that flooring materials and adhesives are suitable for the anticipated interface temperatures. Some timber flooring products and glues can tolerate only relatively low temperatures (below 27ºC) at the interface to the underlying surface, and this must be considered at the design stage. Adequate measures must also be provided for thermal expansion of the floor and covering. Pipe spacing

Pipe spacing for an underfloor heating layout can be approached in two different ways: either optimal spacing to provide the required heating (or cooling output) or closer spacing for maximum comfort. Advantages of closer spacing are: •

30

There is spare capacity in the system


SYSTEM DESIGN

4

•

The required output can be achieved with lower flow temperatures and possibly increase the heat source thermal efficiency

•

There is flexibility to cope with uncertainties in the floor finish and/or covering by increasing the water temperatures within material design limits.

Installing more pipe in the floor does however mean increased material and layout costs. Also, the higher pressure drop caused by longer loops may trigger a decision to opt for a larger number of shorter loops, thereby raising the cost of the manifolds. So while decreased pipe spacing is generally a good idea for system thermal performance and comfort, it raises the cost. Each project should be assessed on its own merits. Concrete and screed cover

Where pipes are laid directly in a concrete floor or in a layer of sand and cement screed, the thickness of material above the pipes and its thermal characteristics will influence the heat output of the floor, the uniformity of surface temperature, and thermal storage effects. Typical cover over the pipes is 35 mm to 50 mm, though pipes may be laid deeper to provide protection against damage (such as from drilled fixings in factories and warehouses) or to increase the thermal storage capacity. Designers should bear in mind that increasing the thickness of cover (and hence its thermal resistance) will also increase the proportion of downward losses unless underfloor insulation is also upgraded. It also reduces the responsiveness, the underfloor system, though the significance of this will depend on the application. 4.5

HEAT LOSS CALCULATIONS

Calculation of heat loss is arguably the most important aspect of an underfloor heating system. If the heat losses are underestimated, it is unlikely that a satisfactory heating system will be installed. Conversely, if the loads are over-estimated, then the underfloor heating scheme may become unreasonably expensive and discarded in favour of a cheaper option. Although heat loss calculations should be carried out in accordance to [18] BS EN 12831 in the same manner as for conventional heating systems, there are some differences in assumptions, as described in the following sections. Design internal temperatures for calculation

Section 2 covered the reasons why underfloor heating should be treated as a radiant system, and that the operative temperature should be used as the measure of comfort. This means that the air temperature can be easily be 1°C or 2°C lower than a radiator or convective heating system providing the same level of comfort.


31

4

SYSTEM DESIGN

This could result in the following scenario for a space intended to achieve an operative temperature of 20°C: For a conventional heating system •

Outside air temperature: -4ºC

•

Inside air temperature: 20ºC

•

Temperature difference: 24°C

For underfloor heating •

Outside air temperature: -4ºC

•

Inside air temperature: 18ºC

•

Temperature difference: 22°C [18]

The base case assumption in BS EN 12831:2003 is that the air temperature, mean radiant temperature and operative temperature are approximately the same value. Annex B of this standard however suggests that where there is a significant difference between the air temperature and the mean radiant temperature (as in the case of underfloor heating), that the transmission heat losses are calculated using operative temperature, and ventilation losses calculated using internal air temperature. This approach could result in a reduction in the estimated heat loss of 6% to 12%. However, any proposal to reduce plant size based on an assumption of air temperature reduced by more than 1°C below the operative temperature, particularly where there are large areas of glazing, should be supported by detailed thermal modelling of the heated space to ensure that comfort is maintained. Nevertheless, a properly controlled underfloor heating system should be always be more efficient in practice than the corresponding convective heating system, simply because the temperature differentials driving the heat losses are lower. Floor and downward losses

To maximise heat transfer into the space, the floor needs to incorporate insulation beneath the heating layer to limit downward losses. [15] BS EN 1264 Part 2 states that downward and edge losses should not exceed 10% of the total calculated losses. [21]

Building Regulations (Approved Documents L1A and L2A) require that the area weighted average U-value for the floor should be less than 2 2 0·25 W/m K. This is equivalent to a ground loss of less than 5 W/m at design conditions. An underfloor system designed to lose less than 10% of the heat input to ground will also comply with the requirements of the 2 Building Regulations, although the specific loss (in W/m ) may be higher. 2 Ideally, designers should aim for less than 10% of the input, or 5 W/m , whichever is the lower.

32


SYSTEM DESIGN

4

[11]

The Domestic Building Services Compliance Guide 2010 sets different insulation standards for exposed ground floors, intermediate floors, wet systems and electric systems (see Appendix D). As heat flows from a hot body towards a cooler one, heat from the room will not be lost downwards past the hotter underfloor heating pipework. This means that the design heat losses for the space (used to determine the underfloor heating pipework layout) should not include any heat losses through the floor where there are heating pipes. The floor losses are included when sizing the heating plant and main distribution pipework system. If a floor area is only partially heated, then the heat loss through the unheated area should be added to the design heat loss of the space in the usual way. For the purposes of this calculation, the boundary of the heated area can be considered as one pipe space beyond the outer pipes. Room volume

In buildings with high ceilings it may be appropriate make allowance for thermal stratification effects that result in increased temperatures, and [18] therefore increased heat losses, at high level. BS EN 12831 Annex B suggests increasing the design heat load by up to 30% for ceiling heights between 5 m and 15 m, depending on the type of heating system. As underfloor heating produces much less stratification than other forms of heating, there is no need to increase the design heat load in this way, even for very high spaces. Infiltration

The total ventilation rate is the designed ventilation rate (natural and/or mechanical) plus the infiltration rate. In the past, underfloor heating systems installed in older, leakier buildings had the potential to reduce infiltration rates. This was probably because the strong convection currents associated with conventional radiators were not being created. This prompted some designers to reduce the standard assumptions for infiltration heat losses in the design heat load calculations. Today, new or substantially renovated buildings are subject to airtightness testing as a requirement of the Building Regulations, and it is unlikely that this particular effect would be very significant. Normal ventilation assumptions for the type of building/activity should therefore be applied. For housing, the infiltration rate in the Building Regulations Standard Assessment Procedure (SAP) is now assumed to be q50/20 where q50 is the measured air permeability at 50 Pa. As the reasonable limit for air permeability is 10 m³/(h.m²), an infiltration rate of 0·5 m³/(h.m²) can be used an upper limit for assessing the effect on heat load. (Note that the envelope area includes the floor.)


33

4

SYSTEM DESIGN

For other buildings, the Building Regulations Part L Simplified Building [22] Energy Model (SBEM) embodies a more complex calculation that takes into account measured air permeability at 50 Pa, internal stack effect, wind speed and building profile. In practice, calculating design heat inputs for large or complex buildings is best tackled through computerbased design tools that also provide the SBEM outputs required for planning and regulatory compliance. Allowance for intermittent heating

Certain underfloor heating systems with low thermal mass (mainly floating floor systems) can be operated much like a radiator system. Higher thermal mass systems (pipes embedded in concrete or screed) react much more slowly. Control strategies and their implications are discussed in Section 4.11 and Section 5. [18]

If the heat load calculation is carried out to BS EN 12831:2003 , the design load may already include an appropriate allowance for intermittent heating in normally occupied buildings (residential and non-residential) and no further allowance should be made. Note that the assumption in [18] BS EN 12831 is that the overnight temperature (or temperature between successive occupied periods) will not drop more than 3°C below the occupied temperature. This will probably be true in new buildings that are heated on a daily basis, but may not be true for older buildings with poorer standards of insulation (or those used less frequently.) These situations can normally be catered for by modifications to the control strategy to allow night set-back and/or extended pre-heat times, rather than by raising the design heat load. Heat pump systems

Where it is proposed to use a heat pump to serve the underfloor system, the additional assumptions detailed in BS EN 15450:2007 Heating Systems [23] in Buildings - Design of Heat Pump Heating Systems should be used. Although underfloor heating systems with heat pumps are ideally sized to operate with a flow temperature of 35°C, this may be too low to provide sufficient heat output for all forms of floor construction. Conventional heat pumps are generally capable of operating with flow temperatures up to 55°C, but the coefficient of performance (a measure of efficiency) declines rapidly as the flow temperature is increased. 4.6

SYSTEM SIZING FOR HEATING

Once the building heat loss calculations have been carried out, the underfloor heating system itself can be designed. [15]

Although BS EN 1264-2 describes how to calculate floor output from first principles, underfloor heating manufacturers simplify the designers task by providing output charts or tables that relate to their own system [15] and components as described in BS EN 1264-3 .

34


SYSTEM DESIGN

4

Alternatively, manufacturers (or their approved installers) may offer computer-aided design services based on the Standard and their own [24] product data. BS EN 15377 may also be used to work out outputs for floor structures that are not covered in BS EN 1264, and when test data is unavailable. The information provided in the following sections illustrates the basic steps in designing an underfloor heating system. It is recommended that architects or services designers contact an underfloor heating specialist early in the design process to ensure that the most appropriate system is provided. The information will, however, enable the reader to better appreciate the important issues and factors involved in underfloor heating, and enable them to communicate more effectively with a specialist designer or installer as the process moves from design to installation. Required heat output

Once the heat loss for a particular room or space has been calculated, the heat output per square metre needs to be established. This is done by identifying the total area available for installation of underfloor heating and dividing the heat output requirements by this area. This will result in a required heat output per square metre which then forms the basis of subsequent calculations. Heat required in the space (W) Total heated floor area available (m2 )

= Required heat output (W/m2 )

When determining the area available for installing the heating, consideration needs to be given to how the room or space is going to be used. For example, underfloor heating for a bathroom should not be installed in the flooring below the bath or toilet, so these areas should be discounted from the available floor space. Similarly, in a kitchen, the pipework should not be installed below kitchen cabinets and appliances, and a space of approximately 100 mm should be left clear around the perimeter of all rooms to allow for carpet fixings. In retail spaces there may be counters or display cases, while in offices there may be filing cabinets and other fixtures. The designer must consult with the client to assess whether the heated space is fully flexible or whether certain areas should be excluded and the extent to which re-zoning may need to occur in the future. If heated areas are covered with thermally insulating structures, the effect of the build up of heat in those areas should be considered. Similarly for cooling, there may be an increased condensation risk if cooled areas are covered. In the worst case, the obscured floor temperature will approach the current flow temperature.


35

4

SYSTEM DESIGN

Floor surface temperature

Once the heat input requirement has been established it can be used to determine the required floor surface temperature:

ΔTα =

q

α floor

t floor = ti + ΔTα

t floor = ti +

q

α floor

where: ΔTα is the floor surface temperature differential (tfloor - ti) tfloor is the mean floor surface temperature (ºC) ti is the operative temperature (ºC) 2 q is heat output required (W/m K) 2 αfloor is the surface heat transfer coefficient (W/m K). 2

For approximate calculations a value of 11 W/m K can be used. The CIBSE uses a different calculation where q = 8·92 (tfloor – ti). In the example given tfloor would work out to 27·2°C. 2

For a heat output requirement of, say, 70 W/m , and operative temperature of 21ºC, the average floor surface temperature would be: ⎛ 70 ⎞ t floor = 21 + ⎜ ⎟ = 21 + 6·4 = 27·4°C ⎝ 11 ⎠ Exactly the same calculation can also be used for underfloor cooling, although the surface heat transfer coefficient is reduced. Experiments by Costic for different operating conditions and surfaces found values 2 2 2 between 6 W/m K and 8 W/m K with an average of 7·1 W/m K. Pipe spacing

The required surface temperature and consequent heat output are achieved by varying the pipe spacing, circulation rate and flow temperature. The depth of pipe and thermal properties of the floor structure and covering are usually constrained by other aspects of the overall building design. To arrive at the required heat output for each zone, designers of commercial buildings generally base the spacing of pipes on pre-determined flow and return water temperatures. This gives the benefit of all underfloor circuits in the system being able to run on the same water temperature. Flow rates can be locally varied during commissioning to achieve the required mean water temperature for each loop. An example of a sizing chart is shown in Figure 15 on next page. This chart is specific to a particular manufacturer’s system, the size of the pipe, and the depth of screed over the pipe. In this case the pipe is 16 mm HDPE with a wall thickness of 1·5 mm covered by 50 mm of screed. Manufacturers produce a series of similar charts covering their range of products, including diffusion plate variants.

36


SYSTEM DESIGN

4

Figure 15: Simplified product-specific sizing chart 300 24 23

21

250

)K

20

ro

om

19

(T

16

te m pe

Limit curves at 35°C

50

at er ex ce ss

150

17

ra tu re

200

300

13 12

M ea n

Limit curves at 29°C

11 10

100

9

50

300

40

8 7

35

50

15 14

w

Heat output W/m2

m-

T

18

Floor surface excess temperature (Tfloor-Troom) K

22

30

6

25

5

20

4

15

3

10 5

0.03 0.04 0.05

50

10 0

0

15 0

0.02

20

0.01

30 0

R - value of floor covering (m2K)/W

0.00

Pipe spacing mm

0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15


37

4

SYSTEM DESIGN

To determine the pipe spacing for a given flow temperature and heat output, a horizontal line should be drawn for the required heat output on 2 2 the upper left hand axis (Output W/m ), in this case 55 Wm . This intersects the series of diagonal lines representing the mean water excess temperature. The other end of this line crosses the right hand axis (Floor surface excess temperature) at 5K. A second horizontal line is drawn from the lower left hand axis corresponding to the resistance value of the floor covering, in this case 2 0·06 m K/W. This intersects the series of curved lines representing different pipe spacings. Assuming a room temperature of 20°C and a mean flow temperature of 35°C, the excess is 15K. A vertical line is then dropped from the point 2 where the 55 W/m horizontal line crosses the 15K excess temperature 2 line. The point at which the line connects with the 0·06 m K/W horizontal line represents the optimum pipe spacing (between 150 mm and 200 mm). The overall input data and results are: • • • • •

2

Heat requirement: 55 W/m Internal temperature: 20°C Floor surface temperature: 20 + 5 = 25°C Mean water temperature: 35°C Pipe spacing: 175 mm (approximate)

Assuming a 5K flow-return temperature difference, the flow temperature will be 37·5°C and the return temperature 32·5°C. In this example, the surface temperature of the floor is well below the limit of 29°C for general areas and would therefore be deemed acceptable. The published version of the graph contains a number of limit curves (only the extremes of which are shown as red lines in the example) that correspond to the maximum output at a given pipe spacing that would not exceed these surface temperature limits. Residential projects are more likely to use standard spacings and pre-formed templates for convenience. In that case the designer would chose the next available standard spacing that is closer than the calculated spacing. Table 9 shows a tabular version of similar information taken from the [25] CIBSE Underfloor Heating Design and Installation Guide , which contains tables for a number of typical floor constructions. Some manufacturers also produce their own information in this format. To find the pipe spacing, the table is inspected for the heat output at the mean water temperature that is closest to the required value. The associated surface temperature is then compared to the allowable limit. This gives an approximate idea of the required spacing but the table is not ideal for interpolation between standard spacings. Also, multiple charts are required to deal with different floor coverings. Note also that the tables in the CIBSE Underfloor Heating Guide are for generic floor constructions and should not be used for detailed design purposes.

38


4

SYSTEM DESIGN

Table 9: Performance table showing heat outputs to BS EN 1264 for 16mm OD PE-X/PE-RT underfloor heating pipes embedded within 75mm floor screed (50mm screed thickness above pipe) – floor covering resistance of 0·00 m2K/W Maximum floor surface temperatures Occupied areas

= 29 ºC

Rλ B = 0·00 m2 K/W

Bathrooms

= 33 ºC

(eg ceramic tiles)

Peripheral areas

= 35 ºC

Pipe spacing intervals VA mm 100

150

200

250

300

4

3·4

Mean water temperature

Design room temperature

MWT

TR

ºC

ºC

1. W/m2

2. ºC

1. W/m2

2. ºC

1. W/m2

2. ºC

1. W/m2

2. ºC

1. W/m2

2. ºC

15

92·0

23·3

79·0

22·3

68·5

21·4

59·7

20·6

52·0

20·0

18

73·2

24·8

62·9

23·9

54·5

23·2

47·5

22·6

41·4

22·0

20

60·6

25·7

52·1

25·0

45·1

24·4

39·3

23·9

34·3

23·4

22

47·9

26·6

41·1

26·0

35·7

25·5

31·1

25·1

27·1

24·7

24

34·9

27·5

30·0

27·0

26·0

26·6

22·6

26·3

19·7

26·1

15

123·2

25·9

105·8

24·5

91·8

23·3

80·0

22·3

69·6

21·5

18

104·5

27·4

89·7

26·2

77·8

25·2

67·8

24·3

59·1

23·6

20

92·0

28·3

79·0

27·3

68·5

26·4

59·7

25·6

52·0

25·0

22

79·5

29·3

68·3

28·4

59·2

27·6

51·6

26·9

44·9

26·3

24

66·9

30·2

57·5

29·4

49·8

28·8

43·4

28·2

37·8

27·7

Pipe requirement Lm/m2 10

30

35

40

45

50

5

6·7

1. Heat emission q

2. Average floor space temperature AFST

15

154·3

28·3

132·5

26·6

114·9

25·2

100·1

24·0

87·2

22·9

18

135·6

29·9

116·5

28·3

101·0

27·1

88·0

26·0

76·7

25·1

20

123·2

30·9

105·8

29·5

91·8

28·3

80·0

27·3

69·6

26·5

22

110·7

31·9

95·1

30·6

82·5

29·6

71·9

28·7

62·6

27·9

24

98·3

32·9

84·4

31·7

73·2

30·8

63·8

30·0

55·6

29·3

15

185·3

30·8

159·2

28·7

138·0

27·1

120·3

25·6

104·8

24·4

18

166·7

32·3

143·2

30·5

124·2

29·0

108·2

27·7

94·2

26·5

20

154·3

33·3

132·5

31·6

114·9

30·2

100·1

29·0

87·2

27·9

22

141·9

34·4

121·8

32·8

105·7

31·5

92·1

30·3

80·2

29·4

24

129·4

35·4

111·1

33·9

96·4

32·7

84·0

31·7

73·2

30·8

15

216·4

33·2

185·8

30·8

161·2

28·9

140·4

27·3

122·3

25·8

18

197·7

34·7

169·8

32·6

147·3

30·8

128·3

29·3

111·8

28·0

20

185·3

35·8

159·2

33·7

138·0

32·1

120·3

30·6

104·8

29·4

22

172·9

36·8

148·5

34·9

128·8

33·3

112·2

32·0

97·8

30·8

24

180·5

37·8

137·8

38·0

119·5

34·6

104·2

33·3

90·7

32·2

Occupied area Peripheral area Not recommended Source: CIBSE Underfloor Heating Design and Installation Guide[25]


39

4 4.7

SYSTEM DESIGN

SYSTEM SIZING FOR COOLING

If the space needs to be cooled to a specific condition, the design cooling load should be calculated by normal methods taking account of outside temperature, solar gains and internal heat gains. The design then proceeds in the same manner as for heating design, based on the available chilled or cold water temperature and need to maintain safe operating temperatures. The key issue is that the floor should not be operated at a temperature that could cause condensation on the floor surface or within covering layers. The cooling effect available from hard impermeable surfaces will therefore be greater than for carpeted surfaces as the minimum top surface temperature will necessarily be higher than the need to prevent condensation on the underlying floor. If cooling is non-critical or the system is primarily designed for heating then the interest may be in estimating the availability of cooling from the underfloor system sized to the heating requirement. Typically the cooling output is likely to be around half of the heating output, even with chilled water. This is mainly a consequence of the lower temperature differentials (between the mean floor circuit temperature and the internal ambient) and lower heat transfer coefficient for cooling compared to heating. Cooling performance of proprietary products may be published as charts or tables or not at all. If no cooling information is available then estimates of cooling performance can be made by calculating the required floor surface temperature to provide the necessary cooling, and adapting the heating data for the same temperature difference between the floor surface and mean flow temperature (see Appendix D). Figure 16 shows a cooling chart for the same floor construction as used in Figure 15. This suggests that for the same pipe spacing (approximately 175 mm) the floor would achieve a cooling output of 35 W/m2 when the mean water temperature was 12.5C below the room temperature. This would result in a floor surface temperature of 5C below room temperature. The floor surface temperature must always remain above the dewpoint of the air in the space to avoid condensation.

40


SYSTEM DESIGN

4

Figure 16: Simplified product-specific sizing chart for cooling

60

8

50

ro om -

Tm

7

T

6

ra tu r

e

25

em pe

40

rt

5

un

de

20

te r

30

ea M

15

n

wa

4

3

20

10

2

10 5

1

0.03 0.04 0.05

50

0.02

15 0

0.01

10 0

0.00

Pipe spacing mm

0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15


41

4 4.8

SYSTEM DESIGN

SYSTEM WATER FLOW RATE

Once the flow and return water temperatures have been established, by whatever method, the water flow rates for each circuit can then be calculated. This is done in the same way as for any other water-based heating system. The water flow rate can be calculated from the formula:

m =

Q c p . ΔT

where: m is the mass flow rate (in kg/s) Q is the heat output required (in kW) cp is the specific heat of water (4·18 kJ/kg.K) ΔT is the temperature difference (K) 2

In the foregoing heating example, the heat output is 55 W/m and the 2 temperature drop 5K. If the room size is 20 m then the total heat output is 1100 W (1·1 kW). The mass flow rate is therefore 0·053 kg/s. 4.9

SYSTEM WATER PRESSURE DROP

Depending on the system design, pump pressure may need to be sized on the total resistance of the system, including boiler and distribution pipework up to the manifolds as well as the actual underfloor pipework circuits. Alternatively, if the pump is only serving the manifold and underfloor circuits it needs to be sized accordingly, and another pump provided for the primary circuit. The system water pressure drop will depend on the hydraulic arrangement of the system, and the type of pipe used. Details of the frictional characteristics of the particular underfloor heating pipe to be used can be obtained from manufacturers and underfloor heating specialists. If the pressure drop on a particular loop is too high due to the length of the loop or the required flow rate, there are two options: split the single loop into two loops or increase the pipe diameter. Increasing the pipe diameter will reduce the flow velocity and pressure drop but also influence the heat output per unit area of floor (assuming the same spacing). The effect is accounted for in BS EN 1264.

4.10 LAYOUT

Previous sections covered the calculation of the basic design parameters for underfloor systems, including flow and return temperature, pipe size, depth and spacing. Once these aspects have been settled there remains the issue of getting the heating (or cooling) water from the main plant into the floor. The appropriate selection of the number and locations of manifolds is a key part in the design and installation of a well-controlled and costeffective system. It is strongly recommended that the design is developed in consultation with an underfloor heating design specialist and the installer.

42


SYSTEM DESIGN

4

The designer should first consider the overall shape and layout of the building and any operational constraints. For instance, if a large building is to be occupied on a multi-tenant basis, it may be undesirable for the manifolds serving a particular area to be located in space occupied by another tenant. Second, the designer should consider the routing of primary distribution pipework and the hydraulic capacity of manifolds. Modular manifolds can typically serve between two and twelve underfloor circuits, but the total flow rate also influences the bore and costs of the manifold. In some cases it may be appropriate to use two pairs of manifolds in the same location. There may be an initial tendency for the designer to use as few manifolds as possible in order to reduce capital costs, such as when dealing with a large open-plan area like a factory or warehouse. In this instance it may seem reasonable to provide a single pair of flow and return headers to serve the one large area. However, this may result in both short and long runs of pipe between the manifold and heated zone and possible congestion around the manifold itself. Practical problems may also arise if the manifold is not placed in the room or area being served. Pipework may need to be double-stacked through a corridor, for instance, in order to get to the heated zone. This may result in local overheating. Even in a single house, the pipework layout can be simplified by using separate manifolds on each floor level. The careful selection of the size and locations of manifolds can help make the cost of an underfloor heating system more competitive compared with that of a conventional system by reducing the amount of primary distribution pipework (primary pipework in this case refers to the pipework before the underfloor heating manifolds). This is particularly applicable where the distribution pipework for a conventional system would normally need to be run from a central distribution route, such as a corridor, to each radiator or convector in adjoining rooms. Systems with more than one boiler or heat source are usually designed with a low velocity header. Systems using heat pumps as the heating and/or cooling source need to have a buffer vessel to avoid short cycling of the heat pump compressor. The distribution and control of heat and cooling is discussed in Section 5. 4.11 CONTROL

As with most aspects of underfloor heating design, there are alternative ways of providing controls for the system. Generally the control system will consist of electronic room temperature controllers for each zone, linked to a master controller. There may also be inputs from underfloor, outside air and manifold temperature sensors. A dewpoint sensor may be used in cooling applications. The master controller controls the pumps and manifold valves and also links to the heat source. In one or two zone systems a single controller may combine these functions. In large commercial systems a building management system may provide the required functionality.


43

4

SYSTEM DESIGN

Figure 17 and Figure 18 illustrate domestic and small commercial applications respectively. Both are shown with optional radiators, although underfloor-only systems are preferred to maximise the energy efficiency benefits of low temperature heat sources. This may also allow the underfloor circulation to be driven directly by the primary pumps rather than as a separately pumped mixing circuit (see Section 5). Figure 17: Typical schematic for a domestic underfloor heating system

Figure 18: Typical schematic for a commercial underfloor heating system

44


SYSTEM DESIGN

4

Both hard-wired and wireless zone temperature controllers are available. Wireless controls provide maximum flexibility of location and save on installation costs. Batteries in battery-powered devices will need to be changed periodically. The Domestic Building Services Compliance Guide 2010 recommends that each room in a house with underfloor heating should have its own temperature control device with weather compensation of flow temperature. Ideally the room temperature sensor should be responsive to both the air and mean radiant temperature, such that the control point can be set in relation to the operative temperature (the best measure of comfort). An air temperature sensor alone will not respond perfectly to changes in operative temperature, for example as solar gain varies through the day. Nevertheless the majority of systems are still controlled on the basis of air temperature. It is strongly recommended that the flow temperature to the floor be controlled through a weather compensation algorithm. This raises the floor temperature as the weather gets colder and will both mitigate the effect of air temperature control and improve energy efficiency. The same principle applies to electric underfloor systems. Control valves for individual pipe loops are integrated with the manifolds. These are typically two-port on/off valves with thermoelectric or solenoid actuators. Balancing valves and flow indicators are also integrated with the manifolds. The manifold flow temperature is controlled by a thermostatic valve or three port electric valve linked to the master controller. Where underfloor heating and/or cooling is operated in parallel with other building environmental systems, such as split air-conditioning systems, the designer and controls engineer need to ensure that those systems are interlocked so that the most efficient system is used whenever possible. The different systems must not operate against each other, for example simultaneous heating and cooling. Controls and control strategies are further discussed in Section 5. 4.12 WARRANTIES AND GUARANTEES

Designers need to examine closely the scope of the system guarantees, and see if they match the allocation of design responsibility, supply of equipment installation and commissioning works. Although underfloor systems are generally straightforward and reliable, designers need to question whether the guarantees relate to the performance of the system in achieving defined comfort conditions, or only workmanship and the reliability of specific components. Similarly, designers need to determine if the guarantees only relate to the replacement of components or toconsequential works. For example, if a 20-year guarantee is claimed for the pipe, the designer needs to ensure that the guarantee includes the cost of breaking out the floor and reinstating it as well as the costs for any damage caused by the pipework failure.


45

4

SYSTEM DESIGN

Guarantees provided by companies who have designed and installed a complete system but specifically excluded certain items from their quotation, and hence subsequent contract, may prove problematic to enforce should problems arise. This is a major issue where an underfloor heating company uses a designer’s or consultant’s information to produce the detailed design. Should the required comfort levels not be achieved once the system is installed and operating, the underfloor heating company could possibly claim that the information provided by others might be at fault. Specifiers should aim to use reputable companies who have adequate insurance cover, and also satisfy themselves that the information being given is correct. 4.13 COSTS

Underfloor heating is often though of as a premium heating solution and therefore inevitably more expensive to install than conventional systems with radiators or fan coils. This is not always the case. Schemes 2 involving over 300 m of underfloor heating can often be substantially cheaper in installation costs than conventional systems while providing lifetime efficiency benefits. Capital costs

The only way to assess the most cost effective solution for a particular project is through an accurate cost comparison of alternative schemes, preferably using a whole life costing methodology. For information about whole life costing see BSRIA’s guide: BG 5/2008, Whole-Life [26] Costing Analysis . There are several reasons why underfloor heating can be less expensive in terms of hardware that a conventional system. For example, costs can be saved on distribution pipework relative to a radiator system, by locating the manifolds in advantageous positions. In a conventional scheme there may be extensive pipework run-outs across rooms to get to radiators located under windows but underfloor heating manifolds can be located nearer to the main service runs. Ideally all projects should be tendered against a detailed specification provided by the designer. Where this not the case, the costs quoted by underfloor heating companies need to be examined carefully to find out exactly what is included. In some instances, the underfloor heating contractor will supply the underlying insulation, whereas in others the builder could supply it. The heat source and/or its installation may not be included in the scheme; the underfloor heating contractor may simply be connecting the manifolds to existing distribution pipework, or pipework provided by others. The room and master controller may or may not be included or installed, or the basic specification offered by the installer may need to be upgraded. Designers need to determine whether system commissioning is included or is an additional cost. Recent estimates from a number of suppliers and installers put the cost for typical underfloor heating installations at around £15 - £40/m2, with large warehouse or factory building-type projects at the cheaper end of the scale and housing at the upper end. This is solely for the underfloor heating element and does not cover the heat source or the distribution pipework from the plant to the manifolds. It does, however, include the floor insulation, installation and room and water controls. 46


SYSTEM DESIGN

4

Running costs

The reasons why an underfloor heating system can produce a comfortable environment at a lower temperature than other systems were discussed in Section 2.4. The difference in air temperature between a predominantly convective system and underfloor heating is approximately 2ºC. This translates into a significant direct reduction in building heat losses and energy consumption. Further benefits can accrue from the use of more efficient low-temperature heat sources, such as condensing boilers or heat pumps. The exact savings that can be expected are difficult to determine, as they depend on both installation details and operational factors. For example, radiator or fan-coil heating systems in commercial buildings would generally be turned off outside working hours, whereas underfloor heating is more likely to be set-back to a lower temperature. However, a well-insulated slab or screed floor should only lose 1·5°C - 2ºC over an eight-hour period, so switching to night set-back may mean that the boiler will not operate except in very cold weather. Lightweight underfloor heating systems heat up relatively quickly and can be regarded as performing more like conventional heating systems (with optimum start). The greatest savings in running costs will be in rooms or spaces with high ceilings, as the underfloor heating system heats only the occupied zone. Although there are no conclusive data, savings in the region of 30 - 50% are frequently quoted as being possible. In rooms with lower ceiling heights, the savings will come from the lower operating temperatures of the system, together with the reduced air temperatures detailed above. In these instances, savings of between 10 - 20% are considered possible.


47

4001 TB BSRIA A4 Ad A/W:AquaCell 8pp Bro A/W

22/12/10

12:27

Page 1

Surface heating and cooling solutions by Wavin

Thermoboard UFH – ensuring the right solution Specifying underfloor heating correctly demands expertise: thorough knowledge, real experience. Thermoboard offers exactly that with the FullSpec Service. All the fast help you want, backed by a product range for any application.

Genuine specialists, dedicated to helping underfloor heating specifiers. For any complex design or routine project, the Thermoboard FullSpec Service is ready. Call the specialists on 01392 444122.

For more information visit: www.thermoboard.co.uk/bsria email: [email protected]

Engineered Water Solutions

Underfloor Heating Solutions Emmeti UK, based in Oxfordshire, distributes and supports underfloor heating, plumbing and renewable energy products to UK customers.

UFH Wiring Boxes

UK Designed Products The company has developed a product portfolio specially designed to cater for the UK plumbing and heating markets and core Underfloor Heating products include: s s s

Manifolds & Controllers

Manifolds and fittings Pipes, Insulation & Accessories Zone controls including : - thermostats - actuators - wiring centres

Product Innovation Emmeti are dedicated to product improvements, and in the last year have launched state of art TST Touchscreen Thermostats, a UK developed EWC-1 Wiring Box, Single Loop Manifolds and the T3 UFH controller. Service & Support The UK team are on hand to answer any questions you may have and to support your product order. Emmeti operate to the highest possible standards including ISO9001 and 14001 and are members of UHMA. All products carry a guarantee and manufacturer’s warranty compliant with UHMA.

Thermostats

Radiator System Manifolds

Plumbing Manifolds

To discuss your requirements call us on 01993 824900, or to find out more about us go to www.emmeti.co.uk.

UFH System Components

Zone Controls

Fitting Systems

T: 01993 824900 W: www.emmeti.co.uk

5 5

DISTRIBUTION AND CONTROL

DISTRIBUTION AND CONTROL All heating and cooling systems need a variety of controls, including sensors, valves and switches, to ensure that the environmental conditions required are achieved for minimum consumption of energy. In many respects underfloor heating is controlled in the same way as a network of radiators. The main differences are lower supply temperatures, slower response and greater thermal storage. Each zone has space temperature sensors, as would be the case with a radiator system, though an underfloor sensor may also be used to prevent the floor overheating. In hydronic systems the zone sensor acts on the manifold valves to interrupt flow to the floor loops when the required temperature is reached. In an electric system it interrupts the power. The manifolds also balance the flows through the floor loops. Usually the flow temperature (or floor temperature) is controlled in response to the outside temperature via a weather compensation algorithm. Typical flow temperatures are up to 45°C with floor surface temperatures up to 29°C in normally occupied spaces. Problems rarely occur with the control aspects of simple underfloor heating systems. Weather compensation in conjunction with the thermal mass of most underfloor heating systems provides a very stable system with excellent heat distribution. The problems that do occur are usually associated with more complex space heating systems using more than one type of heat emitter.

5.1

HYDRONIC UNDERFLOOR HEATING CONTROL

Although the performance of an underfloor heating system is to some extent self-regulating (the heat output from the floor reduces as the temperature difference between the emitter and the room air gets smaller) the key to optimum performance of the system as a whole is an effective control system. The control system must be capable of maintaining room air temperatures within pre-defined comfort limits, with minimum energy consumption by the primary heating plant. In commercial applications, underfloor heating systems have traditionally been arranged as a sub-circuit, (or secondary circuit), drawing hot water from central boiler plant. The boiler plant may serve a variety of other building services systems such as fan coils, air handling unit heater batteries and domestic hot water cylinder primary coils, as well as more local applications such as radiators. Such an arrangement is illustrated schematically in Figure 19.

48



5

Figure 19: Historical pipework circuit arrangement

The main disadvantage of such an arrangement is that the boiler flow temperature must be sufficient to meet the requirements of the highest temperature load. It may be advantageous to segregate high temperature loads (such as domestic hot water) and low temperature loads (such as underfloor heating) to maximise the benefits from condensing boilers or heat pumps. Almost all underfloor heating installations use a pair of flow and return manifolds to connect the underfloor heating pipes in one or more zones, each containing one or more loops of pipe. A manifold is a cylinder with tapped ports into which the control elements can be fitted. This may be constructed using modular elements to provide a variable number or ports or purchased as a manufactured assembly with the required number of ports. In Figure 20 the flow manifold incorporates a manual flow adjuster and indicator for each loop. The return manifold incorporates electrothermally actuated on/off valves for each loop.


49

5


Figure 20: Modular heating manifolds

Source: Based on information from Warmafloor

For small systems, the manifolds, control elements and pump may be supplied as a pre-assembled unit. Figure 22 shows an example, but usually there are more than two ports per manifold. A schematic of this is shown in Figure 21. Figure 21: Schematic of two-port manifold

50



5

Figure 22: Typical pre-assembled two-port thermostatic manifolds with integral pump

Source: Based on information from UK Underfloor Heating

The control elements associated with underfloor heating systems are summarised in Table 10.


51

5


Table 10: Control elements associated with underfloor heating systems

52

Master controller

Dedicated controller or building management system (BMS) outstation to receive input from various sensors and zone controllers and control the operation of electric valves, pumps and heat source(s) as necessary.

Zone controller

Controls the temperature of one or more zones, together with night set-back, frost protection and clock functions.

Space temperature sensor

Usually an air temperature sensor located on a convenient wall in the controlled zone; may be integrated with the zone controller. Some systems employ space temperature thermostats rather than sensors. These are connected to a wiring box that provides the interface to the electrothermal actuators on the manifold.

Outside air temperature sensor

Screened sensor ideally located on the north wall of the building. Used as an input to the weather compensation control algorithm.

Underfloor temperature sensor

A sensor embedded in the screed. This is used to set maximum and minimum temperature limits for the floor and can also be used as part of an optimum start algorithm.

Thermostatic supply valve

Sometimes called an injection control valve. A self-actuating two-port valve with capillary sensor fixed to the flow (or return) manifold to control the flow temperature. The valve mixes system water into re-circulating return water entering the flow manifold.

Thermostatic mixing valve

A self actuating three-port valve that blends the heat source flow with the underfloor heating circuits return water, typically with an installer preset temperature band between 35°C to 60°C. This type of valve proportionally changes both flow and return apertures to produce a mixed flow into the manifold.

Water temperature Controllers - constant

Typically a three-way (or four-way) rotary shoe valve construction. They can be actuated by either a motorised head with a remote system temperature sensor, or a thermostatic radiator valve head with remote capillary heat sensor. They maintain a constant mixed flow temperature.

Water temperature controllers - variable

Typically a three-way rotary valve, with variable orifice capability; sometimes a fourway valve. The valve can also be a three-way ball valve construction. They can be actuated by a motorised head, typically when using a weather compensation controller and its sensors.

Weather compensation controller

Normally using data signalled from more than one sensor, typically both internal and external to the building, these signal the motorised head using algorithms with different flow temperature curves, to reduce or increase the flow temperature.

Flow temperature

Water temperature sensor in the flow manifold linked through the controller to a motorised three-port valve. This enables variable flow temperature control such as for a multi-zone weather-compensated system.

Flow manifold with regulating valves

The regulating valves are used to adjust and balance the flow through multiple circuits in the zone. Some regulating valves incorporate visual flow indicators. The flow manifold may also be fitted with a dial pressure gauge.

Return manifold with twoport control valves

Valves in the return manifold are usually electro-thermal or solenoid operated but may be absent for single zone systems where the pump can be used to start or stop the flow. The manifold may also be fitted with a dial temperature gauge.

Pump

The zone pump is a conventional heating circulator. For small systems the zone pump may be supplied as part of the manifold assembly. Variable-speed pumps with pressure sensing control can minimise energy consumption.

Differential pressure bypass valve

The differential pressure bypass valve allows water to flow around the primary circuit when all the underfloor heating circuit two-port valves are closed, but the pump may still be running.



5

Constant temperature supply

Even where boiler flow temperatures are not constrained by the requirements of other loads they are usually too high to be used directly in the underfloor heating circuit, and so must be reduced before the underfloor heating manifold. In Figure 23, a three-port mixing valve is controlled by a flow temperature sensor (via a dedicated control unit or BMS outstation) to provide a constant flow temperature to the manifold. The manifold has two port (on/off) valves on each loop controlled by a zone controller. Figure 23: Underfloor heating circuit control

Variable temperature supply and weather compensation

A better form of control is to vary the water temperature to the underfloor heating circuits according to the outside conditions and the room or zone temperatures. This is known as weather compensation and ensures the minimum system flow temperature requirement to maximise heat source efficiency. The room or zone thermostats are used to control the temperature in individual rooms, zones and circuits.


53

5


Figure 24: Principle of weather-compensated flow temperature

Weather compensation also reduces the risk of over or under-heating of the floor structure in response to sudden changes in the space temperature. It is recommended for all underfloor heating systems. A control arrangement for modulating the flow temperature of secondary heat distribution circuits is shown in Figure 25. Figure 25: Underfloor heating circuit with weather compensation control

54



5

In some systems where the heat source only serves the underfloor system the flow temperature can be directly modulated at the heat source. This is preferable to secondary modulation and will help to ensure that condensing boilers operate in condensing mode and heat pumps operate at the maximum possible coefficent of performance (COP). Variations for housing

The systems described for commercial buildings can be simplified for use in housing, particularly where there are only one or two heating zones. A typical underfloor heating system for housing will use a condensing boiler or heat pump, where the flow temperature can be modulated to some extent directly at the heat source, in conjunction with one or more control valves to segregate high and low temperature heating requirements. In the case of combination boilers and combination heat pumps, these functions are intrinsic to the boiler or heat pump. In the case of system boilers with domestic hot water cylinders these functions need to be implemented externally. In general it is possible to connect conventional radiators and underfloor heating to a common boiler for single house applications, though careful consideration must be given to optimising the hydronic design while optimising energy efficiency. Connecting conventional radiators and underfloor heating to a common heat pump is not recommended and will almost certainly result in excessive operating costs. If radiators are to be connected to a heat pump the installed area of radiators must be sufficient to satisfy heating needs at a low supply temperature. Figure 26 shows a case where an underfloor heating controller (for example a programmable thermostat) is connected to the central heating programmer in place of a conventional room thermostat. The central heating programmer and associated valves (two solenoid valves or a three-port diverting valve) select for space heating or domestic hot water with the appropriate flow temperature (where that function is available).


55

5


Figure 26: Domestic central heating

Figure 26 also shows a capillary thermostatic control valve to control the temperature from the boiler circuit into the manifold. These valves are relatively inexpensive compared to electric control valves and frequently used in small underfloor heating systems. Note the presence of a pressure relief valve in the bypass to allow for the possibility that the thermostatic valve is closed. Modern systems are likely to use a variable speed circulator (pump) with pressure sensing control to reduce energy consumption. Alternatively, a three-port valve with electronic control could be used in the same manner as in commercial systems, provided that a regulating valve is fitted as the bypass valve to balance the pressure drop through the underfloor circuits. Night set-back and optimum start/stop

Night set-back is simply an automatic adjustment of air temperature set points to reduce the heat input to the building at night (or between scheduled operating periods). It is widely used in Northern European housing and increasingly in the UK as an alternative to switching off the heating completely. Night set-back saves energy relative to continuous heating operation, but prevents the building becoming too cold between scheduled operating periods. Optimum start/stop is a function that switches the heating system on or off (or changes the operation mode to night set-back) at a calculated time such that the set temperature is maintained during scheduled operating periods but no longer than necessary. The calculated start and stop times are based on internal and external temperatures. The calculation parameters are established through a self-learning algorithm in the controller (or manually estimated).

56



5

The suitability of night set-back and/or optimum start/stop operation depends on the thermal response of the heating system, the characteristics of the building and the form of weather compensation, as summarised in Table 11. Table 11: Application of optimum start and night set-back Compensation by heat source modulation

Compensation by secondary circuit modulation

Fast response

Night set-back only

Night set-back + optimum start

Slow response

Compensation only

Night set-back only

Optimum start is generally avoided in systems with heat source modulation as it depends on a boost period during which the flow temperature is maximised, but the heat source efficiency reduced. This consideration does not apply to systems with secondary circuit modulation as the heat source flow temperature is already high. Optimum start is of limited benefit in slow response buildings and selflearning algorithms may not work properly. Whether slow response buildings should, or should not, use night setback is more debatable. However, as this is a standard function of most controllers the actual benefits can be evaluated in-situ. 5.2

HEATING AND COOLING INTEGRATION

Many underfloor heating circuits can be supplied with cold water for summer cooling with minimal changes to the hydronic configuration. Typically, cold water will be supplied via a heat exchanger from a ground coil (passive cooling) or heat pump. It is not recommended to connect a ground coil or chilled water circuit directly to the underfloor cooling circuit as this may contain glycol anti-freeze solution that would reduce the thermal performance of the underfloor system in both cooling and heating mode. An underfloor system can be connected directly to a reversible heat pump as this can be controlled to avoid the risk of freezing. Consequently the circulating fluid will not need anti-freeze. When considering a ground-source heat pump in conjunction with passive cooling, designers should consult the installation manual before designing the hydronic integration. This may include specific provisions for passive cooling, particularly where heat pump operation is required for producing domestic hot water during the cooling season. The following comments apply to the general case. Chilled water circuits and heat-pump ground coils contain an anti-freeze solution. It is undesirable to connect these directly to an underfloor system that also provides heating as the circulating fluid solution has poorer heat transfer characteristics than water. Passive cooling solutions therefore use a plate heat-exchanger between the source and the heat sink.


57

5


If the heat exchanger package is fitted with internal circulation pumps for the ground loop and heating circuits, additional external pumps and nonreturn valves may be fitted as shown in Figure 27. The additional pumps should be interlocked to the heat pump controls so that they cannot run when the heat pump is operating. It is not recommended that the passive cooling heat-exchanger is located directly in line with the heat pump heat-exchangers as the combined pressure drop is likely to be too high for the normal circulation pumps. Figure 27: Passive cooling with ground-source heat pump (internal circulation pumps)

If the heat pump is fitted with external circulation pumps then these may be used in conjunction with three-port valves as shown in Figure 28. In this case the three-port valves should be interlocked with the operation of the heat pump. Figure 28: Passive cooling with ground-source heat pump (external circulation pumps)

The circuits shown in Figure 28 could also be used with open loop ground or water source systems provided that the plate heat-exchanger is protected by groundwater filters. 58



5

It is not recommended to put the passive cooling heat exchanger directly in line with the heat pump heat-exchangers as the combined pressure drop is likely to be too high for the normal circulation pumps. The same principles apply when connecting a chiller to a boiler-fed underfloor system. Figure 29 shows the situation where boiler operation is continued during the cooling season for the production of domestic hot water while the chiller also operate to serve some plant during the heating season. Figure 29: Underfloor cooling for a boiler-fed system

Heating and cooling controller

The main difference between heating only and heating/cooling systems is that the zone controller must be capable of controlling a cooling circuit and accept a floor temperature sensor to control or limit the minimum floor temperature. This is to prevent condensation in the structure. Some controllers also include a humidity sensor to reduce the risk of surface condensation by keeping floor surfaces above the dewpoint of air in the space. The required functionality can be achieved with purpose designed underfloor heating and cooling controllers or a programmable BMS controller. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

59

5


In the example shown in Figure 30 (based on a proprietary control system), each room has a separate programmable room temperature sensor for heating and cooling set points, set-back function and operating periods. This is connected to a master controller for the overall system that controls boiler and chiller (or heat pump) operation, heating/cooling changeover valves and room manifold valves. Each room has a humidity sensor that can override cooling set points to prevent condensation. The outdoor sensor is used for weather compensation during heating mode and for input to the control logic for switching from heating to cooling mode. Such a system would be operated in either heating or cooling mode. It is not possible to heat and cool different areas of the building at the same time unless conventional cooling plants (such as split unit air conditioning) are also fitted e.g. in IT server rooms. Figure 30: Cooling system controls

5.3

ELECTRIC UNDERFLOOR SYSTEMS

Electric underfloor heating is usually implemented on an individual room basis with one or more zones per room depending on the floor area. Electric underfloor heating should be controlled in order to: • • • •

maintain the desired temperature in the occupied space control the energy input into each zone prevent over-heating of the floor maintain electrical safety.

Almost all underfloor heating installations will require both floor sensors and air temperature sensors linked to a purpose-designed controller. The main exception is domestic bathrooms that may use floor sensors only. Domestic controllers can be provided with direct switching of up to 3 kW 2 for one zone. This corresponds to around 20 m for a standard output system. Larger zones can divided into sub-zones and switched with slave controllers (or use a higher rated contactor) as shown in Figure 31.

60



5

Figure 31: Mains voltage electric floor heating

Note that it is not usually necessary to lay electric cable heating systems in a serpentine pattern. Most systems are single ended and the only geometric requirement is to maintain the recommended spacing.

In order to provide accurate temperature control and avoid overshoot, electric heating controls may use an adaptive proportional integral (PI) control algorithm. This decreases the energy supply to the floor as the room space temperature approaches the set point and reduces overshoot to provide a more stable environment. The floor sensor for solid floors should be located in a tube buried in the screed underneath the heating mat or heating cables. Weather compensation

There is no direct equivalent to weather compensation for electric underfloor systems. The amount of heat supplied is determined by the zone controller in order to satisfy the space temperature requirement. Night set-back, optimum start/stop, and tariffs

Night set-back and optimum start/stop can be implemented as for hydronic systems. The complicating factor is that it may bebeneficial to operate the underfloor heating to make best use of the electricity tariff. This can mean switching off the floor heating during periods of high cost electricity and switching on the floor heating during periods of low cost electricity even when heat is not yet needed. For example, the Economy 7 tariff for domestic users provides cheaper electricity between 23:30 and 08:30. The cost of operation outside this period is double the Economy 7 tariff.


61

5 5.4


SUMMARY

Underfloor heating systems are usually divided into multiple zones that can be independently controlled. It may be desirable to create multiple zones within the same space, in order for different parts of the underfloor system to respond to local conditions. Some systems used with lightweight floor constructions will have relatively fast response and therefore can be operated more or less as conventional radiator systems and possibly with optimum start. Systems where pipe or heating elements are embedded in thick concrete and screed will have a slow response. Both will benefit from weather compensation. Underfloor cooling with heat-pump based systems may be available for free or at low additional cost. The benefit is likely to be a small reduction in the effective temperature of the space. Underfloor cooling can also be linked to conventional chiller plant and used in conjunction with fan coils or chilled beams, subject to the consideration of supply temperature and condensation issues. If an underfloor system is linked to a heat-pump ground coil for free cooling via a plate heat-exchanger, there will be a loss in cooling capacity due to the temperature difference across the heat exchanger.

62


ENERGY SOURCES

6

6

ENERGY SOURCES The conventional heat source for radiator heating systems has been a gas, oil or coal boiler, producing water at up to 80°C. Underfloor heating systems do not need such a high supply temperature and can make effective use of a wide range of heat sources, several of which generate low carbon dioxide emissions. Even where an underfloor system is connected to a condensing boiler, that boiler can operate much more efficiently than it would do with a radiator system. This is because it should be fully condensing under all operating conditions other than during the simultaneous provision of domestic hot water. Low temperature, low carbon heat sources for underfloor heating include: • • • • •

6.1

CONVENTIONAL BOILERS

Biomass boilers Various forms of heat pump Combined heat and power plant Solar thermal panels Wind turbines.

Under Building Regulations prevailing at the time of publication almost all gas and oil boilers installed for domestic and small commercial applications must be of the condensing type. That means they should be capable of operating under conditions where the heating circuit return temperature is lower than the dewpoint of the gases produced by combustion of the fuel. This means that latent heat associated with the water produced by combustion of the fuel can be used for extra input. The potential improvement in efficiency for condensing boilers is slightly larger than the latent heat effect, as older boilers were deliberately designed with restricted efficiency to limit the possibility of inadvertent condensation that could result in corrosion problems in the heat exchanger. However, condensing operation only occurs when the return temperature is low. For conventional radiator systems, that will mainly occur during the initial part of the heating period, when the system is cold. Underfloor heating systems, on the other hand, allow the boiler to work in condensing mode for most (if not all) of the time and therefore maximise boiler efficiency. Condensing boilers are usually gas (more commonly natural gas but also LPG) or oil-fired. On larger output units, burners have modulating controls to match the heat demand as closely as possible. This reduces fuel consumption and carbon dioxide emissions. In cases where an underfloor system is connected to a conventional noncondensing boiler, careful consideration must be given to the heating circuit design to avoid low return temperatures and frequent cycling under low load conditions, as both will be detrimental to the life of the boiler. This situation might occur where an underfloor heating system is added to an existing heating system. All new systems should endeavour to use condensing boilers where possible.


63

6 6.2

ENERGY SOURCES

BIOMASS BOILERS

Biomass is any plant-derived organic material that renews itself over a short period. Biomass energy systems are based on either the direct or indirect combustion of fuels derived from those plant sources. The most common form of biomass is wood, in the form of chips, pellets or logs burned in purpose-designed boilers. Other possibilities include the production and subsequent combustion of biogas produced by either gasification or anaerobic digestion of plant materials. Liquid biofuels can also be used, but these are also in demand as transport fuels and therefore relatively expensive. The use of biomass is common in Austria and Scandinavia. The environmental benefits relates to the low primary energy input relative to the energy produced. This can range from a four-fold return on the energy input for biodiesel to an approximate 20-fold energy return for woody biomass. Figure 32: An integrated biomass boiler and fuel delivery system

The direct combustion of wood-based fuel sources is likely to be the most practical use of biomass in space heating applications. Potential wood fuel sources include solid wood, wood off-cuts, woodchips, pellets and briquettes. Typical examples of woody biomass include willow short-rotation coppice and miscanthus (perennial grass). Table 12 lists the properties of various common biomass fuels.

64


6

ENERGY SOURCES

Table 12: Typical properties of biomass fuel Fuel

Energy density by mass

Energy density by mass

Bulk density

Energy density by volume

Energy density by volume

GJ/tonne

KWh/kg

Kg/m3

MJ/m3

KWh/m3

7 – 15

2–4

175 – 350

2000 – 3600 600 1 –

15

4·2

300 – 550

4500 – 8300 1 300 – 2300

18 – 21

5 – 5·8

450 – 800

8100 – 16800

2300 – 4600

Wood pellets

18

5

600 – 700

10800 – 12600

3000 – 3500

Miscanthus (bale)

17

4·7

120 – 160

2000 – 2700

Wood chips (very dependent on moisture content) Log wood (stacked – air dry 20% moisture content) Wood (solid, oven dried)

560 –

000

750

Features of a good quality large-scale biomass boiler include: •

Thermal efficiency greater than 85%

•

Emissions at full load less than 250 mg/m CO, 150 mg/m dust and 3 300 mg/m NOx

•

Automatic cleaning of the boiler heat-exchanger and automatic ash removal

•

Remote monitoring of the boiler operating parameters.

3

3

The operational characteristics of biomass boilers differ significantly from gas and oil-fired boilers. Start-up times are longer, heat retention within the boiler means that heat may be transferred to the heating medium for a considerable period after boiler shutdown. Although most biomass boilers are designed to allow modulation of the boiler output down to typically 30% of the maximum output, they are not suited to frequent modulation. It is common practice to incorporate a thermal storage buffer tank into systems. Underfloor heating systems should not result in rapid changes in modulation for the boiler. However for efficient combustion with low emissions, biomass needs to be burned rapidly and at a high temperature. The hydronic system design requirements are therefore similar to those for non-condensing conventional boilers. Biomass supply and storage considerations

Before committing to investment in biomass boilers it is extremely important to evaluate the security of supply, and reach provisional agreements with suppliers regarding availability and cost of fuel. Biomass plant is expensive and cannot be converted to a different type of fuel if the intended source of supply ceases to be available. An on-site biomass storage facility may need to hold a considerable volume of fuel, depending on the type of fuel, the boiler capacity and the rate of consumption. For wood chips storage, needs may be several times


65

6

ENERGY SOURCES

the volume of the boiler room. The main purpose of the store will be to keep the biomass dry and protected from rain and groundwater. Biomass can be delivered by tipper truck (for below ground storage) or blown into a silo (as with pellets). This requires good access to site and around the storage facility for delivery trucks. Bunkers or silos can be either purpose-designed by specialists and built on site, or prefabricated from an off-the-shelf design. Ventilation will be required in order to keep the biomass dry and possibly to aid further drying. Ventilation also helps prevent the composting of the biomass and the formation of moulds, the spores from which can present a health risk. Composting of wood chips can be minimised by limiting the depth to a maximum of eight to ten metres. Large stores of biomass will require regular turning. Drainage should be provided within the store to allow the removal of water (inadvertent ingress of water and water used for cleaning purposes). Methods to transport the fuel from the storage facility to the biomass boiler include: • • • • •

Gravity feed or chute Screw-type auger feed Conveyor belt Bucket conveyor Front loader bucket grab.

Successful fuel transport is a major issue in the maintenance and reliability of the overall plant. 6.3

HEAT PUMPS

A heat pump is a device that takes heat from a source and transfers it to a sink at a higher temperature. This is the reverse of the natural flow of heat from a hot source to a cold sink, but requires energy to drive the process. The efficiency of a heat pump is measured by the ratio of the heat output to the energy needed to drive the process. This is known as the coefficient of performance (COP). Heat pumps in general are defined in terms of the nature of the source and sink. Ground-source heat pumps extract heat from the ground and transfer it to air or water for space-heating and/or domestic hot water production. Air-source heat pumps largely extract heat from the outside air. Most heat pumps for heating applications are based on a vapour compression cycle as shown in Figure 33. Working fluid evaporates by extracting heat from a low temperature source; the vapour is compressed mechanically and condenses back into a liquid state giving up its latent heat as useful heat. The liquid then expands through a valve causing a drop in pressure and partial vaporisation before re-entering the evaporator for the cycle to be repeated. The compressor is usually driven by electricity but gas engine devices are also known.

66


6

ENERGY SOURCES

Figure 33: Closed cycle vapour compression heat pump

The vapour compression cycle is by far the most common cycle for commercial heat pumps. It has been successfully applied in refrigeration and air conditioning equipment for many years and combines efficiency, reliability, compactness and safety at reasonable cost. The disadvantage of vapour compression heat pumps for traditional hydronic heating applications is that the coefficient of performance declines with increase in condenser temperature. Therefore electric heat pumps are not generally cost-effective compared to gas boilers at the temperatures required for a conventional radiator system (at least 60°C flow at full load). Underfloor heating systems work at lower temperatures and therefore benefit from much higher COPs making heat pumps much more attractive. Table 13 shows how the COP of a ground-source heat pump varies with temperature. Table 13: Example variation of ground-source heat pump COP with temperature Heat distribution system (supply/return temperature) Floor heating (30oC/35oC)

4·0 o

o

Low temperature radiators (35 C/45 C) o

o

Conventional radiators (50 C/60 C) 1

COP1

3·5 2·5

o

Heat sources at 5 C

In simple terms, if the COP is greater than the ratio of the electricity price to the gas price, an electric heat pump will have lower operating costs than a condensing gas boiler. Although price of electricity to domestic consumers has historically been around four times that of natural gas, by October 2008 the ratio had decreased to 3·7. This means that electric heat pumps connected to underfloor heating are becoming attractive in terms of running costs compared with a gas-fired boiler. For more expensive fuels, such as oil and LPG, heat pumps already have a clear benefit.


67

6

ENERGY SOURCES

Note that the COP is the efficiency measured at one operating condition, and will vary with weather conditions and heating load. The average COP over a year (total heat supplied divided by total energy input), is known as the seasonal performance factor (SPF). SPF will normally be lower than the design condition COP, and lower for a system that provides domestic hot water, than, a system used solely for underfloor heating (but so will the seasonal efficiency of a boiler). While operating costs of heat pumps may be similar to gas-fired boilers, the reduction in carbon dioxide emissions is very significant, even when using grid electricity. For example, a condensing boiler working at 100% efficiency (net calorific value basis) will deliver heat with emissions of 0·194 kgCO2/kWh, while a heat pump working at a COP of 3·5 on grid electricity will deliver heat with emissions (at the power station) of 0·121 kgCO2/kWh. That represents a 38% saving in carbon emissions. The unique feature of heat pumps is that they can be reversed to provide cooling. Ground-source heat pumps

Closed-loop ground-source heat pumps extract heat from the ground using a long loop of buried pipe. This can take the form of a shallow buried coil (laid around 2 m under the surface) or a vertical loop in a borehole (up to 120 m deep). The relationship between ground temperature and atmospheric temperature varies with depth. Below 10 m the ground temperature is constant and similar to the annual mean air temperature (approximately 11-12°C at the UK latitude). Even at two metres depth, the variation of ground temperature during the year is much less than the variation of air temperatures (the ground is warmer than the air in winter and cooler than the air in summer). Extracting heat from the ground will gradually lower its temperature, but provided that such extraction takes place over a large area, the effect will be small and the heat content will be replenished by solar gain during the summer. The two main factors affecting heat transfer to a ground collector are its surface area (a factor of the pipe length and diameter) and the thermal properties of the ground. The ground collector may be installed vertically or horizontally. The choice of a vertical or horizontal system depends on the available land, local soil type, excavation costs, and the topographical features. The area required by for the collectors can be estimated from Table A.2 [27] in BS EN 15450 (based on VDI 4640 Part 2) as shown in Table 14. This is based on central Europe conditions and so can be considered conservative for the UK.

68


6

ENERGY SOURCES

Table 14: Maximum extraction rates for buried ground coils Specific heat extraction rate, W/m2 Ground quality

Dry, non-cohesive soil Moist cohesive soil Water saturated sand or gravel

Operating period 1800 hours per annum


10

8

20 to 30

16 to 24

40

32

Source: EN 15450

The collector is a series of plastic tubes often arranged in vertical coils in a slit trench or horizontal loops laid in a wide trench. The coils are laid in trenches dug with a backhoe or chain trencher. In general, trenching costs are higher than piping costs per linear metre, so systems using multiple pipes in one trench may be economic, although the energy collected per metre length of pipe will be reduced (depending on ground conditions). Figure 34: Horizontally laid coils

Coiled pipework can be used in a horizontal or vertical profile. The buried depth should be at least 1·5 m for horizontal loops, with minimum coverage of 0·6 m for vertical loops. Deeper is better. The diameter and spacing of the tubing within the collector area is a compromise between heat transfer considerations, pressure drop and cost. Common tube sizes are 25 mm, 32 mm and 40 mm, the maximum recommended length is shown in Table 15.


69

6

ENERGY SOURCES

Table 15: Recommended maximum length for different pipe sizes Pipe nominal diameter, mm

Maximum recommended pipe run length, m

DN 25

100

DN 32

200

DN 40

400

Vertical borehole collector systems are used where space is limited. They require less pipe and pump energy. Boreholes are generally 100 mm to 150 mm diameter and between 50 m and 120 m deep. They can be installed in most soil and rock types but dry sandy soils with low thermal conductivity should be avoided. Homogeneous porous rocks like chalk are easy to drill and good for heat transfer below the water table, whereas rock-like gravel beds or sandy strata may require grouting to prevent collapse. Even granite is comparatively easy to drill and produces good results due to its high thermal conductivity. In the UK, all boreholes are grouted to improve thermal contact between the tube and the surrounding rock. The grout tube goes into the borehole at the same time as the heat collection tube is inserted. Grout is then pumped down into the borehole from the bottom up as the grout tube is gradually extracted. Indicative values for maximum heat extraction rates (per borehole) are shown in Table 16. More detail on specific ground and rock types is given in BS EN 15450. Table 16: Maximum extraction rates for close loop boreholes Specific heat extraction rate, W/m Ground quality

Dry gravel or sand



< 25

< 20

Moist clay

35-50

30-40

Massive limestone

55-70

45-60

Sandstone

65-80

55-65

Granite

65-80

55-70

Basalt

40-65

35-55

Source: BS EN 15450

Adjacent boreholes need to be spaced far enough apart to ensure that there will be negligible thermal interference between them. A separation of at least 5 m and preferably up to 15 m is advisable. In general, a smaller number of deeper holes will be most economical, require least land and will take advantage of the fact that the undisturbed ground temperature rises (and remains stable) with greater depth. The loops from multiple boreholes are brought together in a manifold chamber to allow for balancing and isolation when necessary.

70


ENERGY SOURCES

6

Although the cost of boreholes is generally estimated in terms of total metres drilled, a major part of the cost is bringing the drilling equipment to site. Larger drilling rigs mean faster drilling, therefore boreholes for large developments (multiple housing or medium large commercial applications) with multiple boreholes will be more cost effective than those for a single house or small commercial building. Closed-loop ground-source heat pumps have several advantages over other heat pump technologies. These include: •

High reliability (few moving parts, no exposure to weather)

•

High security (no visible external components to be damaged or vandalised)

•

Long life expectancy (typically 20-25 years for the heat pump and up to 50 years for the ground coil)

•

Low noise

•

Low maintenance costs

•

No combustion or explosive gases within the building

•

No flue or ventilation requirements

•

No local pollution.

The main market for ground-source heat pumps is new, individual housing with underfloor heating. Total sales in Europe for 2006 topped 100 000, although the UK accounted for less than 1000. The main reason for historically low sales in the UK has been the unfavourable price ratio between electricity and gas. The retrofit market is potentially very much larger than new build in all countries but still limited to applications where a low temperature heat distribution system can be fitted. Other ground-source technologies that should be mentioned but are less common in the UK are listed below. •

Horizontal drilling Not actually horizontal but at a shallow angle to the surface. Similar to closed-loop boreholes in but drilled radially from a central point.

•

DX ground-source Direct expansion (DX) heat pumps pump liquid refrigerant directly through the ground coils. This system is common in France and some other countries as it is potentially more efficient than using brine (anti-freeze solution). Installation requires specialist skills and any damage to pipework can result in a significant refrigerant leak.

•

Thermal piles The heat collection tube is integrated with the building concrete foundation pipes. If the seasonal heating and cooling loads are reasonably balanced, this solution works well for city sites where open space is limited. It is not so good for heating-only applications as there is limited solar contribution to replenish ground heat.


71

6

ENERGY SOURCES

•

Carbon dioxide heat pipes A sealed stainless-steel tube containing liquid carbon dioxide is inserted in a vertical borehole to depths of up to 80 m. This functions as a heat pipe with natural circulation of the CO2 which reduces pumping costs. Heat is transferred to a conventional heat pump via a heat exchanger fitted to the top of the tube. The heat pipe is considered more environmentally friendly than a conventional brine (anti-freeze) circulation loop as any leakage will not harm the ground water.

•

Open loop ground-source Pumps ground water through the heat-pump heat-exchanger. Although this is a very efficient process, it is subject to environmental regulation and requires a water abstraction licence from the Environment Agency.

Water-source heat pumps

Water-source heat pumps are those that can extract heat from a convenient lake, river or similar source. Like ground-source systems they can be direct or indirect. Indirect systems use a submerged heat exchanger and are generally preferred to open loop systems on the grounds of reduced maintenance. Open loop systems require filtration and other measures to prevent material clogging up the heat-pump heat-exchanger. It is also important to ensure that no environmentally damaging material could enter the water-source in the event of a system failure. Closed-loop water-source systems can use a submerged coil of the same pipe used in ground-source systems, although this has to be ballasted to prevent it floating. A new approach is to use a submerged flat-plate heatexchanger. This is similar in size and appearance to a panel radiator but manufactured from stainless steel (or for marine applications, titanium). These flat-plate heat-exchangers are installed upright in a frame. They can provide high heat transfer rates and are a compact system. Unlike other systems they are resistant to biofouling and self-ballasting. The recently completed system at Kings Mill Hospital in Mansfield used 140 Slim Jim panels to serve heat pumps providing 5·0 MW heating and 5·4 MW cooling from a local lake. Air-source heat pumps

The majority of air-source heat pump installations are air-to-air systems such as reversible split air-conditioning units; air-to-water systems are also common. Air-source heat pumps extract heat from the outside air by means of a direct expansion (DX) refrigerant coil. This results in external condensation and possibly ice formation on the coil. Clearly the COP will vary through the year as the outside temperature and humidity levels vary. The coil will need to be periodically defrosted, interrupting the heat flow. Generally the seasonal performance factor (SPF) will be lower than an equivalent ground-source heat pump, but air-source still has a number of practical advantages: • • •

72

Flexible installation location, indoors or out Minimal space requirement Cheap to install as no ground works required.


ENERGY SOURCES

6

The main disadvantages are potential noise from fans in outdoor units. Supplementary heating may be needed in very cold weather. An alternative is the exhaust air-to-water heat pump. This uses the heat content of ventilation air mechanically exhausted from the building. The major benefit is that the source temperature is typically 18-20°C, which is much higher than atmospheric air during the heating season. Therefore the SPF is higher than for outside air-source heat pumps. Secondly, the single package unit is located inside the building with acoustic attenuation so noise issues are reduced. Thirdly, the unit can be operated with an exhaust temperature slightly above freezing to avoid icing of the evaporator. Exhaust air-to-water heat pumps have become the popular form of heat pump for small residential applications (apartments) particularly in Sweden and Austria. They are beginning to be installed in the UK. Packages can be space heating only, heating plus domestic hot water, or reversible heating and cooling. Installation is straightforward but care must be taken with the design and balancing of the internal supply and exhaust ventilation paths to comply with Building Regulations. Adverse air flows through the occupied spaces should be avoided. 6.4

COMBINED HEAT AND POWER PLANT

Combined heat and power (CHP) has been around for more than 100 years but in recent times there has been renewed interest in small systems that can be installed in buildings and as part of district heating systems. The basic point about CHP is that, while the overall efficiency of the system is no greater than a boiler, a significant fraction of output is available as electricity, which is a more valuable form of energy than heat. Not only can there be economic advantages in generating heat and electricity from on-site CHP rather than buying the latter from the grid, but also the overall carbon emissions are lower. The UK Government therefore sees CHP as a key technology in reducing carbon emissions from the built environment and supports its adoption with various regulatory and financial incentives. However, CHP is not cost-effective in all circumstances. It needs a substantial base load to allow for year-round operation and this cannot be achieved through space heating alone. Good applications include hospitals (with domestic hot water demand being a significant fraction of total energy use) and leisure centres with swimming pools. A new approach to extending useful operating hours is to make use of summertime CHP heat generation with absorption chilling. This provide cooling as well as heat and power (trigeneration). This is only viable for installations larger than 500 kWe though some smaller packaged systems are under development. Note that CHP systems are rated in terms of their electrical output (kWe) or thermal output (kWth). The relationship between the two depends on the system but for commercial use, a gas engine based system will produce approximately 350 kWth for 100 kWe. At the other end of the market various 1 kWe micro-chp appliances are becoming available. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

73

6

ENERGY SOURCES

These are designed as replacements for wall-hung gas-fired boilers and use either Stirling engines or fuel cells to generate electricity as and when there is a demand for heat. Whether these appliances will become popular remains to be seen. In the micro CHP or mini CHP sector for non-domestic applications (say 100 – 1000 kWe) the predominant technology is the spark-ignition gas engine (based on transport or marine engines) though gas turbines are also used. Heat arises from three sources: •

Exhaust gas heat exchanger – available as medium temperature hot water or steam (up to 120°C)

•

Engine jacket cooling – available as low temperature hot water (up to 90°C)

•

Lubricant cooling – available as low temperature hot water (up to 60°C).

In practical terms a commercial CHP package can be interfaced with an underfloor heating system in place of a conventional boiler, or make preferential use of the lower grade heat available from the cooling circuits. 6.5

WIND TURBINES

Most wind turbines are designed to generate electricity and may be appropriate for an electric underfloor heating system. Small turbines (less than 10 kW peak) can be grid-connected via an inverter to directly offset mains electricity consumption, connected to a battery storage system, or connected to an electric storage space heating system. The latter application is popular where there are restricted fuel choices. It also avoids some of the cost and complexity of mains connected or battery systems.

6.6

SOLAR COLLECTORS

Although it is possible to consider using a solar thermal collector as the main energy source for an underfloor heating system, this is unlikely to be cost effective. It would still require a full-size conventional heating source for mid-winter heating. A more sensible approach would be to consider solar thermal mainly for domestic hot water although it is possible to take advantage of the minor contribution to space heating if that is technically feasible. An exception would be where a solar thermal system is to be used for swimming pool heating during summer. In that case a larger area of collector may be justified. Solar thermal collectors use the sun’s energy to heat water, usually for domestic purposes such as washing and cleaning. Although most heat is available during the summer, such systems can collect useful amounts of energy for up to 10 months of the year. There may be surplus energy available to space heating at either need of the normal heating season.

74


ENERGY SOURCES

6

Solar thermal collectors can be categorised into the following types: •

Glazed flat-plate collectors

•

Evacuated tube-collectors

•

Unglazed plastic or low temperature collectors.

Unglazed collectors are mainly used for swimming pool applications. Flat-plate collectors (see Figure 35) comprise a metal absorber plate in a glazed rectangular housing. The absorber plate is made from copper or aluminium and with a special coating to improve solar absorption. Copper tubes are fixed to the back of the absorber plate to circulate the heat transfer fluid and absorb the heat from the plate. Figure 35: Flat-plate solar collector

The collector assembly is thermally insulated on its back and edges and surmounted by a transparent cover. This transparent cover can be of plastics but is typically of low-ferrous glass. Special glass coatings may used to reduce reflections and increase efficiency. The heat transfer fluid is typically water, which is circulated through the collector to a heat store or heating coil in a hot water cylinder. Two approaches to frost protection are possible: either anti-freeze is added to the heat transfer fluid or the system is designed so that it drains down when the circulating pump is switched off. In evacuated tube collectors the absorber is a heat pipe mounted in an evacuated glass tube to eliminate the convective heat losses. Heat is transferred from the absorber tube to a heat exchange header using the heat pipe principle. The heat transfer fluid (water) flows through the header to a heat store or heating coil in a hot water cylinder. Although generally flat-plate collectors provide a higher peak capture of solar energy per unit area, evacuated tube collectors continue to provide useful heat for a greater proportion of the year. They are thus potentially more useful when considered in the context of space heating.


75

6 6.7

ENERGY SOURCES

SUMMARY

Underfloor heating can be used with all conventional boilers and renewable energy sources. Condensing boilers are a good option where mains gas is available and provide good efficiency with minimum capital cost. Heat pumps can be used to minimise carbon emissions but are much more expensive than boilers. They can be financially attractive where there is no mains gas and the alternative fuels are expensive. Other heat sources such as CHP, biomass boilers and solar collectors may be viable in certain circumstances and can also contribute to a low carbon solution.

Table 17: Summary of potential low carbon heat sources for underfloor heating Technology Biomass

Conventional CHP

Fuel cells

Ground-source heat pumps

Air-source heat pumps

Solar water heating

Small scale wind power

Characteristics

Uses plant-derived organic material such as wood chips and pellets or derived liquid and gaseous fuels.

Generates both electricity and heat from engines or gas turbines using fossil or renewable fuels.

Generates both electricity and heat by an electrochemical process.

Extracts heat from ground. Heat can be used for space heating and domestic hot water.

Takes up heat from ground and releases it at higher temperatures. Heat can be used for space heating and domestic hot water.

Can be integrated with underfloor heating applications but not suitable as the sole source of heat.

Turbine/generator converts wind energy to electrical power and/or heat. Not suitable as the sole source of heat.

Functionality

High. Can replace gas/oil-fired boilers. Direct combustion (particularly wood chips) requires large fuel storage facility.

Medium. Requires predictable yearround base load for best performance. Not suitable for underfloor heating alone.

High. More flexible than conventional CHP. Not suitable for underfloor heating alone.

High. Systems can be run in heating or cooling mode.

High. Systems can be run in cooling mode.

Medium. Proven technology with a range of collectors for different operational requirements.

Best performance for pole mounted turbines in open, rural locations. Can be linked electric heating systems.

Controllability

Medium. Modern direct combustion systems have automatic fuel feed and reasonable turndown ratio.

Limited turndown ratio. Not suitable for intermittent operation.

High

New heat pumps use inverter controlled compressors to provide good part load performance and improved controllability.

New heat pumps use inverter controlled compressors to provide good part load performance and improved controllability.

High

High

Cost effectiveness

Medium. More expensive than conventional boilers.

Medium. Requires high utilisation of heat. Not cost effective for underfloor heating alone.

Low. Currently available cells are very expensive but expected to reduce in price as technology develops.

Medium. Still Medium relatively expensive compared to conventional boiler plant.

Medium. Needs a large collector area to make a useful contribution to space heating.

Low to medium. Depends greatly on available wind conditions and local cost of fuels.

Reliability

High for direct combustion systems.

Medium. Proven technology.

Medium. Expected to be reliable but long-term reliability data not yet available.

High. Relatively few High. Relatively few Medium to high. moving parts. moving parts. Output depends on Proven technology. Proven technology. weather conditions.

Low to medium. Output depends on weather conditions.

Maintenance requirement

Medium for direct combustion systems.

Medium. Requires regular planned maintenance.

Medium. Few moving parts. Fuel cell stack has finite life.

Low. Sealed for life Low. Shorter life refrigerant circuits than groundbut ancillaries may source. need maintenance. F-gas regulations may require checks for refrigerant leakage.

Low

Medium. Requires annual safety inspection and maintenance. Access may be an issue.

CO2 saving

High

Medium. Can be improved if biomass fuel is used.

Medium. Depends on full utilisation of generated heat and fuel source.

Medium if using grid electricity. High for renewable electricity. High efficiency is dependent on relatively low supply temperatures in heating mode.

High during spring and autumn. Some energy is still needed for pumps.

Medium to high.

76


Medium if using grid electricity. High for renewable electricity. High efficiency is dependent on relatively low supply temperatures in heating mode.

FLOOR FINISHES

7

7

FLOOR FINISHES Underfloor heating can be used with virtually all floor finishes and surface coverings provided that the maximum material and interface temperatures are respected. Surface coverings with high thermal resistance should obviously be avoided where possible as they need higher flow temperatures or closer pipe spacing to achieve the required heat output. These factors may also have a negative effect on system efficiency and installation cost. This does not preclude the use of thermally resistive floor coverings such as carpets, vinyl flooring, wood block flooring and laminates but does mean that the effect of such coverings must be carefully considered and allowed for in the design. This section briefly describes common floor finishes and coverings that may be used with underfloor heating systems, including thermal properties and practical constraints.

7.1

SURFACED CONCRETE AND SCREED

Surface-treated concrete and screed (without any further covering) are found in many warehouse and manufacturing contexts. Decorative finishes are increasingly being used as an alternative to floor tiles. In basic applications the concrete or screed surface (after grinding) is treated with a protective coating such as a two-part epoxy paint to resist wear, abrasion, spalling and dust formation. The coating also provides resistance to water penetration. A wide range of colours is available and the paint can incorporate anti-slip material. Other floor paints are based on polyurethane and acrylic systems, the latter being used where low emission of volatile organic carbons (VOC) is a requirement. With epoxy and polyurethane systems it is vital that the underlying concrete and screed is fully cured (a minimum of three weeks for a cement-based screed unless otherwise advised by the manufacturer) as the coating will trap residual water vapour. The coating process can be described in several steps: 1. After the concrete and/or screed are fully cured, operate the underfloor heating system for a significant period prior application of the coating (minimum seven days) 2. Allow the floor slab to fully cool (minimum 24 hours) 3. The company applying the coating should check that the residual moisture content of the floor slab is suitable. If not then return to step 1 4. Apply the coating. Low temperature heat may be supplied to the floor slab in cold ambient conditions but the surface temperature must stay within the limits imposed by the coating manufacturer 5. Allow the coating to fully cure before re-applying full heating heat to the floor.


77

7

FLOOR FINISHES

Acrylic resin compounds can be applied to fresh concrete as a hardener but these will normally be used in conjunction with a conventional topcoat. The top-coat should be applied as described on previous page Other decorative finishes include acid-etched and polished concrete with an acrylic sealer and terazzo. These are used as an alternative to tiled surfaces in shopping centres and other indoor public spaces. None of the floor finishes described above will significantly affect the heat transfer or surface temperature compared to the same thickness of basic screed or concrete, or impose additional temperature restrictions for underfloor heating applications once the treatment has fully cured. Relevant standards:

7.2

MASONRY FINISHES OVER CONCRETE AND SCREED

•

BS 8204-1:2003 Screeds, Bases and in-situ Floorings. Concrete Bases and [28] Cementitious Levelling Screeds to Receive Floorings. Code of Practice

•

BS 8204-2:2003 Screeds, Bases and in situ Floorings. Concrete Wearing [29] Surfaces. Code of Practice

•

BS 8204-3:2004 Screeds, Bases and in situ Floorings. Polymer Modified [30] Cementitious Levelling Screeds and Wearing Screeds. Code of Practice

•

BS 8204-4:2004 Screeds, Bases and in situ Floorings. Cementitious [31 Terrazo Wearing Surfaces. Code of Practice

•

BS 8204-7:2003 Screeds, Bases and in-situ Floorings. Pumpable Self[32 Smoothing Screeds. Code of Practice .

Stone and quarry tiles

Stone and quarry tiles may be laid over all types of underfloor heating, including hydronic systems embedded in concrete or screed and those suspended or within floating floors. In the case of electric heating mats, the mat may be laid between the concrete or suspended floor and the overlying tiles, with an uncoupling membrane and a special thin screed to provide a base for the tile adhesive. Stone and quarry tiles have no inherent temperature limitations but adhesives and grouts must be sufficiently flexible to accommodate a small amount of thermal expansion and contraction without cracking. Special measures are required if tiling over calcium sulphite (anhydrite) screeds. Practitioners should refer to Tile Association publications for specific advice. The following Tile Association publications are available from www.tiles.org.uk/help/publications.shtml: • • •

78

Tiling to Heated Floors Movement Joints in Internal Tiling Tiling to Calcium Sulfate Based Screeds


FLOOR FINISHES

•

7

BS 5385-5:2009 Wall and Floor Tiling. Design and Installation of Terazzo, Natural Stone and Agglomerated Stone Tile and Slab Flooring. Code of Practice

Large areas of flooring may need expansion joints to reduce floor surface stresses. Ceramic tiles

Ceramic floor tiles are frequently used in bathrooms and domestic kitchens. While the same considerations apply as for stone and quarry tiles, the tiles are thinner (10 mm). As the coefficient of linear expansion -6 1 of concrete (7 to 14 × 10 K− ) is around twice that of ceramic tiles (3 to -6 1 6 × 10 K− ), flexible adhesives and grouts must be used to avoid cracks developing between tiles and creating a path for water penetration. This particularly important for bathroom floors that run with a high surface temperature (up to 35°C). Relevant standards that apply include:

7.3

MASONRY FINISHES OVER FLOATING OR SUSPENDED FLOORS

•

BS 5385-3:2007 Wall and Floor Tiling. Design and Installation of Internal and External Ceramic Floor Tiles and Mosaics in Normal [33] Conditions. Code of Practice

•

BS EN ISO 10545-8:1996 Ceramic Tiles. Determination of Linear [34] Thermal Expansion .

The general considerations are similar to tiles laid over concrete floors, but there may be increased risk of cracking due to flexing of the underlying structure. Wooden floors or sub-structures will need to be stiffened with 18 mm plywood sheets (secured with screws at 150 mm centres) before the underfloor heating system is laid.

7.4

THERMOPLASTIC TUBES

Thermoplastic tiles should not be used over underfloor heating. Thermoplastic (PVC) tiles with bitumen adhesive were widely used as a general-purpose intermediate finish for concrete floors in new housing, intended to be overlaid with carpet, carpet tiles or vinyl flooring. Nowadays the use of thermoplastic tiles over concrete has been largely superseded by improved screed finishes so that the final floor covering can be laid directly. Note that old thermoplastic tiles may contain asbestos. This should be considered when removing and disposing of old tiles.

7.5

IMPACT FLOORING

Impact flooring includes vinyl and linoleum products of various thickness and surface characteristics. The products are usually supplied in rolls and glued to the underlying floor surface. These are widely used in both domestic and commercial applications (particularly bathrooms and kitchens) and in schools and hospitals.


79

7

FLOOR FINISHES

Vinyl floor coverings become softer as temperature rises, therefore there is an increased risk of permanent depressions caused by concentrated loads such as furniture castors. Adhesives also need to be suitable for operation at an elevated temperature. As vinyl floor coverings are thin, latex screeds are used as a surface preparation on normal screeds or concrete to reduce the visibility of any slight surface irregularities. Linoleum consists of a cured mixture of linseed oil and wood dust (and other ingredients) on a jute backing. It is more expensive than vinyl and more difficult to lay, but hard wearing (subject to continued maintenance). It is claimed to be more environmentally friendly as it uses natural components. Adhesives for vinyl or linoleum must be suitable for use at an elevated temperature. 7.6

CARPET AND UNDERLAY

The thermal performance of carpets and underlays is measured in TOG. A TOG value is equivalent to the thermal resistance (measured in 2 W/m K) multiplied by ten. The combined TOG value of multiple layers is the sum of the TOG values of the individual layers. The maximum TOG rating for floor coverings used in conjunction with underfloor heating systems is 1·5 TOG as specified in BS EN 1262. Typical good quality woven carpets provide TOG values between 1·5 and 2·0 and underlay also adds to the thermal resistance. Special low thermal resistance underlays (TOG values less than 1·0) have been developed specifically for underfloor heating applications. Foam backed carpets are generally less suitable for underfloor heating (unless specifically warranted by the manufacturer) as the foam may degrade. Commercial carpet and carpet tiles glued directly to a screed are unlikely to cause problems provided that the adhesive is suitable. High levels of volatile organic compounds may occur temporarily when the underfloor system is first switched on. In 2005, BSRIA carried out a series of tests to evaluate the influence of carpets and underlays on underfloor heating. A summary of these results is available on www.beama.org.uk/en/energy/underfloor-heating/. The conclusion of this work was that the published TOG values for woven carpet with underlay over-estimated the effective thermal resistance when used in underfloor heating applications by approximately 1·0 TOG. However, it is recommended that the designer should still calculate the heat output according to the published TOG value, and treat any benefit of reduced TOG value as an increase in the design margin.

80


FLOOR FINISHES

7.7

WOOD AND LAMINATE FLOORING

7

Wood flooring

All forms of wood flooring from solid parquet and traditional planks to thin layers of natural wood bonded to plywood or medium density fibreboard can be used over hydronic underfloor heating but some are more suitable than others. The main issue of concern is usually expansion or contraction due to changing moisture levels. This may lead to cracking along the grain, particularly in solid wood planks. The general rules are: •

The initial moisture content of the wood should be less than 8% to avoid warping or shrinkage

•

The initial moisture content of the screed should be less than 0·5%

•

The surface temperature of the wood should not exceed 27°C

•

Softwoods such as pine should be avoided.

Wood is a good natural insulator so the interface temperature will be higher than for masonry systems. The effect of any under-layer must also be taken into account. A relevant standard is BS 8201:1987 Code of Practice for Flooring of Timber, Timber Products and Wood Based Panel [35] Products . Laminate flooring

Laminate floor consists of a high density fibreboard (HDF) substrate sandwiched between thin veneers of a resin (melamine) impregnated paper, one of which is printed with a decorative surface. This is typically supplied as tiles or strips with a “glueless” tongue and groove jointing profile. HDF is susceptible to degradation by moisture so a plastic membrane barrier layer should always be placed over concrete or screeded floors. A cushion layer is then placed on the membrane to reduce the effect of any minor floor irregularities and to improve sound absorption. Normal cushion layers for laminate such as polyethylene foam and wood fibre boards have relative high thermal resistance but a thin layer of natural felt (0·8 mm) can be used as an alternative. Several manufacturers produce low thermal resistance products specifically for underfloor heating applications. In general, laminate flooring is suitable for hydronic underfloor heating provided the thermal resistance of the HDF and the cushion layer are taken into account and extra allowance is given for thermal expansion at the edges. Laminate flooring may not be suitable for electric underfloor heating unless specifically approved by the manufacturer.


81

7

7.8

FLOOR FINISHES

EFFECT OF FLOOR FINISHES ON THERMAL PERFORMANCE

In public buildings and general offices a floor covering will normally be specified at the design stage. Subsequent replacements during the lifetime of the building are likely to have similar thermal properties. Hotels and residential property are more likely to experience significant changes to floor coverings so the designer should consider a reasonable worst case situation and ensure that the design assumptions are documented in the operation and maintenance manuals. Apart from the direct effect on heating or cooling output, additional factors that may need to be taken into account are: •

Allowable interface temperatures for the material involved. If allowable temperatures are exceeded for the initial design then the spacing may need to be reduced to achieve the same output at a lower flow temperature

•

The potential effects of obscuring the floor with furniture and the possible use of supplementary floor coverings. This reduces the heat transfer and increases the risk of condensation in cooling applications.

Figure 36 shows the situation where a thin rug has been placed over the carpet. This has resulted in a 4K reduction in the surface temperature compared with the surrounding carpet. On the other hand some books lying on the carpet have raised the surface temperature by localised compression of the carpet and reduction of TOG value. Figure 36: Additional rug placed over carpet

The methodologies for calculating flow temperatures and heating or cooling outputs are described in Section 4. For large projects it is recommended that samples of the proposed floor covering materials are tested to determined their thermal resistance (if this information is not readily available from the manufacturer).

82


INSTALLATION AND MAINTENANCE

8

8

INSTALLATION AND MAINTENANCE As with other forms of heating, a successful underfloor heating system relies on specifying, supplying and installing the appropriate components in the proper manner. Unlike other systems however, certain key actions have to be carried out at very specific stages in the construction process. Some of these cannot be easily rectified or amended should they later be found to be incorrect.

8.1

DESIGN ISSUES

The actual installation process will run more smoothly if careful thought is given to that process throughout the design and specification stage. Regulations

All installation, commissioning and maintenance of underfloor heating systems falls under the general provisions of the Health and Safety at Work [36] etc Act 1974 and The Construction Design and Management Regulations [37] 2007 (otherwise known as the CDM Regulations). The scale and duration of works associated with a small project may not be sufficient to trigger the statutory requirement to notify the Health and Safety Executive (HSE) under CDM Regulations, nor require additional duties in compliance with Part 3 of the Regulations. Nevertheless it is reasonable to follow the principles of Part 3 for managing the safety of projects, including the handling of documentation. The client should appoint a project manager to take responsibility for the project. This would typically cover: •

Defining the scope of the project

•

Drawing up the specification

•

Assembling the design team

•

Planning the overall programme of works and coordinating ancillary activities

•

Signing off the project on completion of all necessary works and satisfactory testing of the completed installation.

Where the project falls under the notification requirements of the CDM Regulations, the client or main contractor must appoint a CDM coordinator and notify the HSE. Other regulations that will apply include (but are not limited to): • • • • • •

The Management of Health and Safety at Work and Fire Precautions [38] (Workplace) (Amendment) Regulations 2003 [39] Personal Protective Equipment at Work Regulations 1992 [40] Electricity at Work Regulations 1989 [41] The Manual Handling Operations Regulations 1992 , amended 2002 [42] The Provision and Use of Work Equipment Regulations 1998 Reporting of Injuries, Diseases and Dangerous Occurrences Regulations [43] 1995 .


83

8


In addition certain equipment supplied in connection with an underfloor heating project must comply with, and be appropriately CE marked to: •

The Low Voltage Directive

•

The Electromagnetic Compatibility Directive

•

The Gas Appliances Directive

•

The Boiler Efficiency Directive.

Note that the Boiler Efficiency Directive is being superseded by the Energy Using Products Directive. This Directive will also include minimum efficiency requirements for other heat sources and equipment that may be included in the system. In general, projects will be subject to the requirements and approvals procedures of the relevant parts of the Building Regulations and Water Regulations. Programme

Resolving issues at the design stage rather than on site invariably saves time and money. There are many potential pitfalls. It is strongly recommended that the design is developed in consultation with an underfloor heating design specialist and the installer. The designer should make sure that there is sufficient time allowed for the works and consider how underfloor installation activity will affect other trades and the general programme. The underfloor specialist may not be appointed at the time the initial builders work requirements are determined by the designer/architect. Consultation with a specialist would be recommended. For example: •

The building must be air and water-tight before installation of the underfloor heating begins. Frost protection may be required thereafter

•

The entire floor area must be free of all other trades while the underfloor pipework is being installed

•

Screed must be laid as soon as possible after the underfloor heating pipework has been installed

•

Routes through the underfloor heating area will be restricted during installation and until the screed is fully cured. Lightweight underfloor systems may need to be temporarily protected against surface damage until they receive their final covering.

The contract administrator or architect needs to develop a programme before the start of the project, in consultation with the underfloor installer, that allows other trades to work in other areas during pipework installation. Although most types of pipework used are fairly robust, heavy traffic over the installation should be avoided. Accidental damage to pipework will be extremely expensive to repair.

84



8

Builders’ work requirements

The underfloor heating installer or underfloor design specialist should inform the architect or design team as soon as possible of the special builders’ work measures required to accommodate the underfloor heating installation. A good example is the build up of the floor. At the start of the project it is essential that the entire design team is aware of the depth required to accommodate the necessary floor construction in the design. Similarly, to avoid unsatisfactory compromises, the number and location of manifolds should be agreed with the underfloor heating design specialist and installer early in the design process. The method of containment should also be agreed, be it in surface-mounted boxes or in cupboards. This information must then be communicated to the design team and other trades to avoid potential conflicts during construction. The design team should also be consulted on more straightforward builders’ work items such as getting pipework from one room to another, through walls and intervening spaces. This may require some input from the architect or structural engineer to ensure that the pipework can pass safely through a wall, and that any special measures that may be required (such as lintels and fire barriers) are specified during design. The flow of information is a two-way process. Other members of the design team must ensure that any changes that they are forced to make are passed on to the project manager for ratification and for assessment of any implications for the underfloor heating design. Managing change in a building project where underfloor heating is being used is very important, as the consequences of moving walls and partitions can be much more serious. In many ways, underfloor heating is less flexible than a radiator-based system, where changes can often be made all the way through the design period and most of the construction period without causing too much disruption. On the other hand, underfloor heating creates fewer constraints, as it does not impinge on the occupied space. Client issues

There are a few crucial issues that need to be carefully considered by the client at a very early stage, which is not normally the case on projects using conventional heating systems. For example, floor coverings are a significant factor in the design as they play a major part in determining the heat output of the heating system. The client's favoured floor coverings may not be suitable and alternatives will need to be discussed. If the floor covering is unknown at the point of design (for example, as in a shell and core and tenant fit-out contract), the design team will have to assume that a conventional floor covering will be used. The prudent choice may also be the worse-case scenario, which might lead to a more expensive installation than would otherwise occur had the floor covering requirements been known. A client may have very definite ideas about where the manifolds can be located, which will raise issues of access. Access from within the heated space may provide a simpler installation, but access from outside the


85

8


heated space may be better for routine maintenance and for meeting any aesthetic requirements. Any fixtures and fittings or equipment that may need to be fixed to the floor will need to be documented and the proposed positions notified to the design team at a very early stage. This will allow the designers to locate the underfloor pipework accordingly. It needs to be impressed upon the client that there will come a point in the design process – earlier than they are used to on more conventional projects – when no more changes to the general structure and floor plan layout can be accommodated in the underfloor system design. Late changes may entail significant cost and disruption to the build programme. Having said that, it is still better to make changes during the design stage than on site. Once the floor screed has been laid, it may be difficult and expensive (or sometimes impossible) to accommodate major changes in over-floor structures without compromising the thermal performance of the system. The client and the design team need to be disciplined in their approach to their design to avoid costly errors. Contracting issues

It is important for the project manager and main contractor to understand the basic principles of the underfloor heating installation so that it may be properly and efficiently integrated into the overall construction process. The project manager and main contractor will need to give extra thought to the sequencing of the works on site to avoid delays and lost production while the pipework is being laid, as the area having the pipe installed needs to be free of all other staff. The contractor also needs to avoid damage to the pipework once it is installed by arranging for the screed to be laid as soon as possible after the installation of the pipework. Several guides recommend that cement and sand screeds are allowed to cure for 28 days prior to the application of heat. In the unlikely case that the pipe is damaged or suspected of being damaged, then the project manager should be informed immediately and agreement reached with all parties on the degree of investigation (such as pressure testing or thermal imaging) and subsequent corrective action. There may also be a lengthy running-up period to actually bring the underfloor system into use and this needs to be allowed for in the site organisation. The contractor should be made aware that the heating cannot normally be used to dry out the structure of the floor and the building. The allocation of responsibilities between the design team, main contractor, underfloor heating installer and other trades needs to be made clear and documented at the tender stage (for further information see [44] BSRIA guide: BG 6/2009, A Design Framework for Building Services ). It is important that any support activity required by the underfloor heating specialist is provided, either by the main contractor or their subcontractors. One of the most common sources of dispute on site is where particular items of work have not been carried out, as both parties assumed that it was being done by the other. 86



8

General issues

Other general issues that need to be checked and closely monitored during the installation works are: • •

• • •

8.2

INSTALLATION PROCESS

The use of the correct tools for working with the particular pipe and fittings There should be no joints in the pipework in inaccessible areas. In the unlikely case that the pipe is damaged on site, purpose-designed couplings or joints can be used as repairs, but they must be in accordance with BS EN 1264 and exactly located and recorded on the project drawings There should be no kinks or creases in the pipework Underfloor pipework should not overlap If there is a risk of freezing before the system is fully operative, the underfloor heating specialist and contractor must agree with the design team a suitable method of preventing damage due to freezing. This may be achieved by providing temporary local heating to raise the ambient temperature, adding anti-freeze or another agreed method.

The actual installation process followed by the underfloor heating specialist may vary from project to project, taking into account the different construction arrangements, contractual agreements and work packages. The following guidance is written in terms of the project manager, whoever that may be in practice. Provision of information

Prior to commencement of the installation, the detailed design information produced by the specialist supplier/installer should be checked against the information or criteria provided originally by the designer/consultant to ensure that what is being installed will suit the purpose for which it is intended. The project manager must check that the relevant design criteria have been adhered to during the detailed design, and approve the calculations of heat losses provided by the consultant. The project manager must also check the heat supply, flow rates and temperatures provided by the underfloor design specialist. These calculations should include a clear statement of the design criteria, assumptions and margins that have been incorporated. Some of the main design criteria are: • • • • • • • • •

Internal and external design temperatures U-values Ventilation rates Individual zones Floor surface temperatures Pipe spacing Floor finish System water temperatures System water flow rates. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

87

8


The project manager and design team must then check the scope and content of the detailed design provided by the underfloor heating design specialist. Things to check include: •

Detailed specification and proposed locations of all manifolds. These should have been agreed during discussions with the underfloor heating design specialist prior to placing the materials order

•

Detailed pipework layout in relation to manifolds and heating zones

•

Detailed specification, arrangement and proposed location of controls. Depending on the scale of the project this may require active collaboration between the building services designer, underfloor heating designer, installation contractor, controls specialist and commissioning engineers. It is also vital to ensure that all necessary controls are compatible

•

Detailed description of the proposed control strategy

•

Fully dimensioned set of pipework layout drawings with threedimensional representations and cut-aways where appropriate. These are to be checked against corresponding design calculations schematics and the latest available architect’s plans.

Installation drawings

The project manager must check the installation drawings that the underfloor heating specialist has produced for the installation prior to commencing work. Pipe routes should be carefully checked for possible conflict with other building elements. Preparation

The project manager must ensure that the main contractor is aware of all the interfaces with the other trades and that all the preparatory work necessary for the installation of the underfloor system has been completed to an appropriate quality. This may typically include holes through walls and laying of insulation (where not provided by the underfloor heating installer). The project manager should also ensure that all other trades are out of the area and the space has been cleaned. Installation of floor insulation

The project manager must ensure that the correct type and thickness of insulation has been used, including the edge insulation. This may be supplied and fitted either by the underfloor heating installer or the main contractor. It is critical to check this, as the main contractor or other members of the design team may have agreed a change to the specification which may affect the performance of the system. This should be double-checked before the underfloor heating specialist starts work. With a suspended floor system, the project manager must ensure that the insulation is installed correctly and that it is adequately supported. The CDM Regulations require that the underfloor heating specialist is aware of the safety implications of the incomplete floor structure.

88



8

General recommendations

The installer will usually be installing a proprietary system of components, backed by detailed installation guidance from the manufacturer or supplier. The following points are generally applicable to hydronic systems: •

The manifolds should be fixed before running the pipework, and the pipework is laid in strict accordance with the approved layout

•

Pipework should not be laid within 100 mm of the perimeter of the space to allow for the later fixing of any carpet edging strips

•

Pipe should be laid straight and should not have any kinks or creases. Bends should be greater than or equal to the minimum bend radius specified by the manufacturer or use pipe bend supports

•

There should be no joints within the pipework loops between flow and return manifolds

•

For suspended or intermediate timber floor systems it may be beneficial for the main contractor to mark out the positions of elements such as internal walls and partitions, sanitary fittings and kitchen cabinets to help ensure that the pipework is laid in the correct positions

•

The correct pipe clipping system should be used and clips fixed at the appropriate distances as recommended by the manufacturer.

Filling and testing

When all the pipe loops associated with a manifold have been completed, that part of the system can be filled and pressure tested. The tests should be witnessed and the results recorded on test certificates. Water for pressure testing must be taken from a clean source (ideally direct from the mains) to avoid the possibility of contaminants entering the underfloor system. Typical test pressures are 1·5 times the working pressure of the system or 3 bar, whichever is the greater. This may vary between materials and manufacturers. Any leak will be evident by a fall in the reading on the system pressure gauge. If testing is performed overnight, changes in temperature may also cause the pressure to drop and so may appear very low first thing in the morning. The project manager should obtain certificates for all tests, signed by all agreed parties. Covering and screeding

Covering and screeding should only be carried out after a successful pressure test, and should be carried out while the pipe is under pressure. Pipework flushing

Although the underfloor circuits are plastics and will therefore not corrode, other parts of the system such as boiler heat exchangers, pumps, control valves (and possibly some of the distribution pipe) will be metal. Also, it is likely that manufacturing and installation residues such as oil, dirt and swarf will be present.


89

8


Main distribution pipework should be cleaned and flushed in accordance [45] with BSRIA AG 1/2001.1 Pre-Commission Cleaning of Pipework Systems and satisfactory water quality achieved before the underfloor system is opened to the distribution system. In order to make this possible the system designer may need to make provision for a separate flushing bypass prior to the manifolds. Figure 37: Example of a flushing bypass

Floor loops should be treated as terminal units and back-flushed through the manifolds. Chemical cleaning and the flushing of heating systems into the foul drain require a permit from the sewerage undertaking. Water treatment

Ongoing water treatment for prevention of corrosion should be appropriate to the materials in the system and include a biocide component. The specified water treatment (including inhibitors and biocides) should be added to the system immediately after flushing. Antifreeze is not normally used as part of ongoing water treatment but may sometimes be used as temporary frost protection measure during precommissioning. Earth bonding

Manifolds and metal systems pipework must be earth bonded. Electric underfloor systems must be earth bonded as detailed in manufacturers’ installation instructions. Controls

Space sensors and associated controllers should be fitted by the underfloor installer or controls specialist at the locations specified by the system designer, and connected according manufacturers’ installation instructions.

90



8

Power supplies

All electrical work must be carried out by appropriately qualified [46] personnel in compliance with BS 7671 and health and safety regulations. Electrical work must comply with Part P of the Building [47] Regulations . The power for hydronic circuit controls may be taken from an appropriately fused spur on the local small power ring. The power for electric underfloor heating be taken via dedicated fused circuits from main distribution boards or sub-distribution boards connected to the appropriate meters. Additional sub-metering may be incorporated in the scheme for energy management purposes. 8.3

COMMISSIONING, BALANCING AND START-UP

Commissioning is the process of bringing a system into use and adjusting the operational parameters to achieve the design intent. When the screed is cured, the system cleaned, flushed, filled, vented and treated with inhibitors and the heat source commissioned, then the underfloor system itself is ready to commission. Commissioning may vary between systems, but the basic steps in relation to hydronic underfloor systems are: 1. Check pressure test and other safety inspection certificates 2. Carry out a visual inspection of the entire system for completeness, satisfactory condition and conformance to design drawings and approved modifications 3. Pressurise the system 4. Open the valves to the main heat distribution and check system pressure 5. Operate the underfloor heating system pumps 6. Balance the circuit valves to the design flow rates 7. Switch on the heat source 8. Check the temperature drop across each circuit and re-balance if necessary. This may not be possible if the commissioning takes place in the summer months 9. Check the correct operation of the control system (this may be done by the underfloor heating specialist or another trade, depending on who installed it). This should include checking the correct operation of all control valves, thermostats, actuators, time control devices including the night set-back function, and outside weather compensation devices 10. Check the flow and return temperatures. Again, this will depend on the weather conditions at the time 11. Check room temperatures 12. Produce the commissioning report 13. Modify working drawings as necessary and produce a detailed set of record drawings.


91

8 8.4


HANDOVER

On completion of commissioning the design team should provide a complete set of project documents to the client or their representative. This should include: •

A description of the system including the design criteria, assumptions and calculations supporting the design

•

Design drawings and as-installed record drawings

•

Inventory of equipment

•

Test and commissioning records

•

Water treatment records

•

Operation and maintenance manuals

•

Equipment warranties

•

Any other documentation required in the client’s project specification.

It is particularly important that clear record drawings are provided for an underfloor heating system, to ensure that pipes are not unwittingly disturbed during work on the floor. Further information can be found from BSRIA guide BG 1/2007 [48] Handover, O&M Manuals and Project Feedback . 8.5

MAINTENANCE

The regular maintenance requirements of each component will be different according to their materials, construction and function, as with any other system. The parts that are common to all heating systems, such as boilers, circulating pumps and motorised valves, can be treated in the normal way. The manifolds should be checked annually for signs of leaks. If these cannot be cured by tightening the fittings, the manifold may need to be dismantled and the washers or seals replaced. The operation of manifold valves should be checked and the indicated flows compared with the commissioning record. The underfloor heating pipework itself should require no maintenance through its life. Inhibitors can be used to prevent the build-up of sludge in other parts of the system. Due to the smooth internal surface of the various types of pipe used in underfloor heating, sludge or scale should not build up. Should it become necessary to flush the pipe through for any reason this can be usually done by disconnecting the loop from the manifolds and using potable water at sufficient mains pressure.

92



8.6

THERMOGRAPHIC SURVEYS

8

A very effective way of checking the quality of the underfloor heating installation (and also to create a record of the position of the pipework within the floor) is to carry out a thermographic survey, preferably immediately after commissioning. A thermal imaging camera provides a false colour video image of a surface, where the colour indicates the temperature. This can indicate not only the routes of the pipework (as shown in Figure 38) and possible problem areas, but also provide an accurate record of floor surface temperatures to compare with the design specification. Figure 38: Colour thermographic image of an underfloor heating installation

Spot measurements can be used to check the temperatures of above-ground pipework and components such as floor return connections. Bear in mind that there may be a significant difference between the surface temperature of plastic pipework and the fluid inside it. The cost of surveys depends on the size of the building or area. A typical survey for a house or small office would start at about £500. When compared to the overall contract values the survey can represent real value, particularly in time saved finding faults.


93

Building Solutions Automotive Industry

ENERGY EFFICIENT BUILDING SOLUTIONS INNOVATIVE UNDERFLOOR HEATING AND COOLING SYSTEMS Thinking about the future, two key elements come to mind - the environment and the next generation. 0VS6OEFSçPPS)FBUJOH$PPMJOH4ZTUFN is one such product which has been proven time and time again in areas of high footfall, providing an environmentally conscious and sustainable solution for large and small scale projects. /PXXJUI#.4QMVHBOEQMBZDBQBCJMJUZ GSPN3&)"6nTo*OUFMMJHFOUDPOUSPMT BOE with a wide selection of global custom-

ers, from sports stadia and commercial enterprises to public buildings such as schools and hospitals, we are DPOæEFOUUIBUXFIBWFCPUIUIFSBOHF and scope of products for your needs. 5IF3&)"6TZTUFNJTUIFQFSGFDU QBSUOFSGPSFOFSHZFGæDJFOUDPOEFOTJOH boilers and for renewable energy solutions and has been proven across both the public and private sectors. Our technical expertise, customer service, innovation and exacting quality

3&)"6-UE )JMM$PVSU 8BMGPSE 3PTTPO8ZF )FSFGPSETIJSF )32/ 5FM'BY&NBJMFORVJSJFT!SFIBVDPN

standards position us at the forefront of the industry and we are proud to have become the preferred choice in PVSæFME - Value - Quality & Reliability 5FDIOJDBM4VQQPSU REHAU - a reputation for excellence Visit www.rehau.co.uk

Uponor systems... Flexible Plumbing Underfloor Heating Pre-insulated Pipe

People marvel at the beauty of a bold architectural design or stunning interior. But some of the most impressive features of modern commercial structures are all but invisible to the naked eye.

• Integrated plumbing, heating and pre-insulated pipe systems that use less energy and perform reliably for years; with 30 years experience in the UK, and a century of company history. • Quality, innovative products proven by decades of testing. • Energy conservation through system design and efficient manufacturing processes. • Partnerships with professionals. Training and support services that let you install our products with confidence and ensure reliable performance.

Contact us to learn how Uponor can support you with your next project:

+44 (0)1455 550355

BMW World, München, Uponor Underfloor Heating & Cooling.

Integrated plumbing, heating and pre-insulated pipe systems that perform reliably for years; with 30 years experience in the UK, and a century of company history.

www.uponor.co.uk

A

APPENDIX

APPENDIX A: EXAMPLE CALCULATIONS The following example serves to illustrate a fixed temperature design methodology using the data tables in the CIBSE Guide. It is based on a bungalow but the same principles would apply to any building. Design criteria

The design criteria that have been used for this particular example are listed here. Each project will have its own data agreed or determined by the design team at the start of the work. Table 18: Design criteria at an external temperature of 5ºC Room

Temperature

Infiltration

ºC

ACH

Floor finish

Kitchen/family

20

1

Hardwood

Utility/WC/coats

16

1

Tile

Living

20

0·75

Hardwood

Hall/dining

20

1

Hardwood

Bedroom 2

16

1

Carpet

Bedroom 1

16

1

Carpet

Ensuite

22

1

Tile

Bedroom 3

16

1

Carpet

Bathroom

22

1

Tile

The temperatures shown are those used for calculation. U-values Table 19: U-values for various construction elements Element

U-value W/m2K

External wall

0·30

Triple-glazed window

2·47

Double-glazed window

3·60

Single-glazed window

4·55

Partition wall

1·70

Ceiling

1·61

Roof

0·25

Downward loss/floor

0·52

Heat losses

The heat losses for each room shown in Table 20 have been calculated by the elemental heat loss method. Note that these calculated losses exclude the floor heat loss in the specific areas with underfloor heating. Losses through the floor are taken into consideration later in the design process. 94


APPENDIX

A

Table 20: Heat losses (excluding floor loss) Room

Heat loss W

Kitchen/family

2 848

Utility/WC/coats

554

Living

2 447

Hall/dining

2 196

Bedroom 2

326

Bedroom 1

636

Ensuite

324

Bedroom 3

324

Bathroom

341

The figures above are those used to size the pipe arrangement in each space and not to size the system plant, as they do not include the downward losses. Required heat output

The net floor area is used with the calculated heat losses in Table 21 to determine the required heat output for each area. The required heat output is simply the heat loss divided by the net floor area. Table 21: Required heat output values Room

Heat loss

Net floor area

Required heat output

Watts

m2

W/m2

2 848

39·2

72·7

554

11·0

50·4

Living

2 447

25·8

94·9

Hall/dining

2 196

34·8

63·1

Bedroom 2

326

9·2

35·4

Bedroom 1

636

14·7

43·3

Ensuite

324

4·2

77·2

Bedroom 3

324

9·9

32·7

Bathroom

341

6·4

53·3

Kitchen/family Utility/WC/ cloakroom

A number of factors may affect the choice of system water temperatures. For this example the following values have been used: •

System water flow temperature: 55ºC

•

System water return temperature: 45ºC

•

System mean water temperature: 50ºC.


95

A

APPENDIX

Floor heat output, pipe spacing and temperature

The notional screed cover in the CIBSE Guide is 50 mm. This is larger than that often used in practice and therefore will tend to underestimate the actual floor output and surface temperatures. The CIBSE Guide provides different look-up tables corresponding to different floor coverings, with indications of maximum desirable floor surface temperature. The data shown in Table 22 has been extracted for a mean fluid temperature of 45°C. Table 22: Pipe spacing at 45°C Room


Covering

W/m2

Room temperature

Pipe spacing

CIBSE output

CIBSE surface

°C

mm

W/m2

°C

Kitchen/family

72·7

Hardwood

20

250

80·1

27·4

Utility/WC/ cloakroom

50·4

Tile

16

300

101·5

25·1

Living

94·9

Hardwood

20

150

101·5

29·1

Hall/dining

63·1

Hardwood

20

300

71·4

26·6

Bedroom 2

35·4

Carpet

16

300

62·1

21·8

Bedroom 1

43·3

Carpet

16

300

62·1

21·8

Ensuite

77·2

Tile

22

300

80·2

29·4

Bedroom 3

32·7

Carpet

16

300

62·1

21·8

Bathroom

53·3

Tile

22

300

97·8

30·8

It is possible to interpolate the CIBSE tables (or BS EN 1264 calculations) to arrive at the ideal spacing for each location. It is more usual to stick to standard spacings (in 50 mm increments) and choose the closest solution that provides at least required output. It is evident from results in Table 22 that several areas could potentially be supplied with more heat input than required, even at 300 mm spacing. In practice, the heat input would be limited by the space control thermostat, but it is preferable to reduce the disparity to improve the quality of control. On the other hand, if the mean temperature were reduced to 40°C then some areas would be under-heated. The obvious solution is to provide separate thermostatically controlled manifolds for the daytime areas and bedroom areas, with the latter set to a lower temperature, as shown in Table 23.

96


A

APPENDIX

Table 23: Pipe spacing at 45°C and 40°C Room


Covering

W/m2

Room temperature

Pipe spacing

CIBSE output

CIBSE surface

°C

mm

W/m2

°C

Daytime areas at 45°C Kitchen/family

72·7

Hardwood

20

250

80·1

27·4

Utility/WC/ cloakroom

50·4

Tile

16

300

101·5

25·1

Living

94·9

Hardwood

20

150

101·5

29·1

Hall/dining

63·1

Hardwood

20

300

71·4

26·6

Bedroom wing at 40°C Bedroom 2

35·4

Carpet

16

300

51·5

20·9

Bedroom 1

43·3

Carpet

16

300

51·5

20·9

Ensuite

77·2

Tile

22

200

82·5

29·6

Bedroom 3

32·7

Carpet

16

300

51·5

20·9

Bathroom

53·3

Tile

22

300

55·6

29·3

System water flow rates

The flow rate through the circuits needs to be sufficient to satisfy both the room loads and the downward losses through the structure. The maximum downward heat loss through the floor should be no greater than 10% of the floor output. This can be used as a default value for the purposes of calculating the required flows. In this sizing method, calculating the exact flow rate necessary to give the required heat input at the selected mean flow temperature is not straightforward due to the interaction between flow rate, mean temperature and heat output. However, the maximum flow rate cannot be greater than that required for the output stated in the CIBSE Guide (including the corresponding downward loss) so that can be used for pump sizing and as the commissioning flow in the first instance. Table 24: Water flow rate Room

Heat loss

Net floor area

CIBSE output

CIBSE input

Total input

Flow rate

W

m2

W/m2

W/m2

W

kg/s

2 848·0

39·2

80·1

88·1

3 453·9

0·083

554·0

11·0

101·5

111·7

1 228·2

0·029

Living

2 447·0

25·8

101·5

111·7

2 880·6

0·069

Hall/dining

2 196·0

34·8

71·4

78·5

2 733·2

0·065

Bedroom 2

326·0

9·2

62·1

68·3

628·5

0·015

Bedroom 1

636·0

14·7

62·1

68·3

1 004·2

0·024

Ensuite

324·0

4·2

80·2

88·2

370·5

0·009

Bedroom 3

324·0

9·9

62·1

68·3

676·3

0·016

Bathroom

341·0

6·4

97·8

107·6

688·5

0·016

Kitchen/family Utility/WC/cloakroom

In practice, flow rates may be varied to cope with any uncertainty over floor finishes or to provide some flexibility for the occupants through the life of the building. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

97

B

APPENDIX

APPENDIX B: CHECKLISTS This Appendix includes checklists for underfloor heating installations. They are also available on the BSRIA website. Designer’s checklist

The person or company preparing the scheme design should complete the designer’s checklist. This checklist is intended to act as an aide memoire to ensure that the installation can begin on site. Underfloor heating specialist’s/ installer’s checklist

The company/s carrying out the detailed design and installation of the underfloor heating system should complete this checklist. Main contractor’s checklist

This checklist should be completed by the main contractor and is aimed at the successful integration of the underfloor heating installation with the rest of the services. Inspector’s checklists – Nos 1-3

These checklists are for the inspector to complete, and plot the progress of the installation from before the start on site to completion.

98


B

APPENDIX

DESIGNER’S CHECKLIST FOR UNDERFLOOR HEATING Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This checklist should be completed by the person responsible for the scheme design (i.e. consulting engineer or architect) prior to commencement of the underfloor heating installation. Any answers that require more than a yes or no or the space in the adjacent box is insufficient should be detailed in the Comments section on the reverse of this form. A copy of this sheet should be kept on site for completion/amendment through the life of the project. It should also be available for inspection by other interested parties as required. 1

Underfloor heating specialist information Contact person: Company: Address:

Tel: Fax: E-mail: 2

Design information

2.1

Has the specification been produced as provided to the underfloor heating specialist?

Yes

No

2.2

Has the detailed design been produced by the underfloor heating specialist?

Yes

No

2.3

Does the detailed design meet the specification?

Yes

No

2.4

Are there any variations to the specification?

Yes

No

No

2.5

Have the calculations been provided?

Yes

2.6

Have the correct design criteria values been used?

Yes

No

2.7

Have the correct drawing backgrounds been used?

Yes

No

2.8

Are the calculations approved?

Yes

No

2.9

Have the drawings been provided?

Yes

No

2.10

Have the correct drawing backgrounds been used?

Yes

No

2.11

Are the drawings approved?

Yes

No

3

Approvals

3.1

Is the underfloor heating specialist authorised to proceed?

Yes

No

3.2

Has the underfloor heating specialist been notified of the approval to start?

Yes

No

3.2

Has the main contractor been notified of the approval to start?

Yes

No


99

B

APPENDIX

Comments:

100


B

APPENDIX

UNDERFLOOR HEATING SPECIALIST’S/INSTALLER’S CHECKLIST Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This checklist should be completed by the underfloor heating specialist/installer prior to commencement of the underfloor heating installation. Any answers that require more than a yes or no should be detailed in the Comments section on the reverse of this form. A copy of this sheet should be kept on site for completion/amendment during the life of the project. It should also be available for inspection by other interested parties as required. 1

Underfloor heating specialist information Contact person: Company: Address:

Tel: Fax: E-mail: 2

Design information

2.1

Has the specification been produced by the designer?

Yes

No

2.2

Has the detailed design been produced?

Yes

No

2.3

Has all the necessary design information been provided?

Yes

No

2.4

Has information on the heat source been provided?

Yes

No

2.5

Does the detailed design meet the specification?

Yes

No

2.6

Are there any variations to the specification?

Yes

No

2.7

Have the calculations been submitted for approval?

Yes

No

2.8

Have the calculations been approved?

Yes

No

2.9

Have the drawings been submitted for approval?

Yes

No

2.10

Have the drawings been approved?

Yes

No

3

Site information

3.1 3.2 3.3 3.4 3.5

Has the builders’ work list been given to the main contractor? Have the builders’ work items been completed? Has the main contractor notified you of the approval to start? Has the work area been cleared? Has the insulation been laid? (if being done by the main contractor)

Yes Yes Yes Yes Yes

No No No No No


101

B

APPENDIX

Comments:

102


B

APPENDIX

MAIN CONTRACTOR’S CHECKLIST Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This inspection procedure should be carried out by the main contractor. Any answers that require more than a yes or no should be detailed in the Comments section on the reverse of this form. A copy of this list should be kept on site for completion/amendment through the life of the project. It should also be available for inspection by other interested parties as required. 1

Design

1.1

Has the designer’s checklist been provided?

Yes

No

1.2

Has the designer’s checklist been completed?

Yes

No

1.3

Is there any outstanding information required?

Yes

No

1.4

Has commencement of the installation been approved?

Yes

No

1.5

Has the underfloor heating specialist provided a builders’ work schedule?

Yes

No

2

Preparation

2.1

Have the work areas been cleared?

Yes

No

2.2

Are any other operatives working in the same area?

Yes

No

2.3

Is the floor ready for installation of the insulation?

Yes

No

2.4

Has all associated builders’ work been completed?

Yes

No

2.5

Is the building watertight?

Yes

No

3

Insulation

3.1

Has the insulation been installed?

Yes

No

3.2

Has the insulation been installed as shown on the drawings?

Yes

No

3.3

Is it of the specified material?

Yes

No

3.4

Is it of the specified thickness?

Yes

No

3.5

Is any remedial work required to the insulation installation?

Yes

No

4

Underfloor heating system

4.1

Has the underfloor heating system been installed?

Yes

No

4.2

Has the system been tested and commissioned?

Yes

No

4.3

Is any remedial work required to the system?

Yes

No

5

Inspection

5.1

Have all inspections been carried out?

Yes

No

5.2

Is any remedial work required following the inspections?

Yes

No


103

B

APPENDIX

Comments:

104


B

APPENDIX

INSPECTION CHECKLIST No. 1 – PRE-COMMENCEMENT INSPECTION Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This inspection procedure should be carried out by the inspector prior to the commencement of the underfloor heating installation. Any answers that require more than a yes or no or the space in the adjacent box is insufficient should be detailed in the Comments section on the reverse of this form. A copy of this sheet should be kept on site and be available for inspection by other interested parties as required. 1

Project information

1.1

Has the project information sheet been provided?

Yes

No

1.2

Has the project information sheet been completed?

Yes

No

1.3


Yes

No

2

Design

2.1

Has the designer’s checklist been provided?

Yes

No

2.2

Has the designer’s checklist been completed?

Yes

No

2.3


Yes

No

2.4


Yes

No

2.5

Has the underfloor heating specialist provided a builders’ work schedule?

Yes

No

3

Main Contractor

3.1

Has the main contractor’s checklist been provided?

Yes

No

3.2

Have parts 1-3 of the checklist been completed?

Yes

No

3.3

Is there any outstanding information in parts 1-3 required?

Yes

No

3.4


Yes

No

4

Preparation

4.1

Have the work areas been cleared?

Yes

No

4.2

Are any other operatives working in the same area?

Yes

No

4.3

Is the floor ready for installation of the insulation?

Yes

No

4.4

Is the insulation being provided by the main contractor?

Yes

No

4.5

If yes, have they installed it?

Yes

No

4.6

Has all associated builders’ work been completed?

Yes

No


105

B

APPENDIX

Comments:

106


APPENDIX

B

INSPECTION CHECKLIST No 2 – INTERIM INSPECTION Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This inspection procedure should be carried out by the inspector immediately following the installation of the underfloor heating pipe, and before any flooring has been installed so that the pipe installation is still clearly visible. Any answers that require more than a yes or no should be detailed in the Comments section on the reverse of this form. A copy of this sheet should be kept on site and be available for inspection by other interested parties as required. 1

Pre-commencement inspection

1.1

Has the pre-commencement inspection checklist been provided?

Yes

No

1.2

Has the pre-commencement inspection checklist been completed?

Yes

No

1.3


Yes

No

1.4


Yes

No

2

Insulation

2.1

Has the insulation been installed?

Yes

No

2.2

Has the insulation been installed as shown on the drawings?

Yes

No

2.3

Is it of the specified material?

Yes

No

2.4

Is it of the specified thickness?

Yes

No

2.5

Is any remedial work required to the insulation installation?

Yes

No

3

Underfloor heating pipework

3.1

Has the builders’ work been completed?

Yes

No

3.2

Has the underfloor heating pipework been installed?

Yes

No

Yes

No

No

3.3

Has the pipework been installed as shown on the drawings?

3.4

Is the pipework of the specified material?

Yes

3.5

Is the pipework of the specified diameter?

Yes

No

3.6

Is the pipework adequately clipped/secured?

Yes

No

3.7

Have the manifolds been installed as shown on the drawings?

Yes

No

3.8

Has the pipework been connected to the manifolds?

Yes

No

3.9

Has the pipework been pressure tested?

Yes

No

3.10

Has the test been witnessed and a certificate issued?

Yes

No

3.11

Is any remedial work required to the pipework installation?

Yes

No


107

B

APPENDIX

Comments:

108


B

APPENDIX

INSPECTION CHECKLIST No 3 – FINAL INSPECTION Site reference:

Date of inspection:

Site address:

Name of inspector:

/

/

Signature:

Site contact name: Telephone no. This inspection procedure should be carried out by the inspector once they have been notified that the installation of the underfloor heating system is complete. Any answers that require more than a yes or no should be detailed in the Comments section at the end of this form. A copy of this sheet should be kept on site and be available for inspection by other interested parties as required. 1

Screed/flooring installation

1.1

Has the screed/flooring system been installed?

Yes

No

1.2

Has the final floor finish/covering been installed?

Yes

No

1.3

Is it to be the same as the specification?

Yes

No

2

Underfloor heating pipework

2.1

Has the underfloor heating pipework been filled and tested?

Yes

No

2.2

Has the pipework been connected to the heat source?

Yes

No

2.3

Has the heat source been tested and commissioned?

Yes

No

2.4

Have the appropriate certificates been provided?

Yes

No

2.5

Has the underfloor pipework been connected to the heat source?

Yes

No

No

No

2.6

Is the underfloor heating system water at working temperature?

Yes

2.7

Is it the same as the specification?

Yes

2.8

What are the water temperatures to/from the heat source system and manifolds?

2.9

Manifold No. 1:

Flow:

ºC

Return:

ºC

Manifold No. 2:

Flow:

ºC

Return:

ºC

Manifold No. 3:

Flow:

ºC

Return:

ºC

What are the water temperatures in the underfloor heating circuits? Manifold No. 1: Circuit No. 1:

Flow:

ºC

Return:

ºC

Circuit No. 2:

Flow:

ºC

Return:

ºC

Circuit No. 3:

Flow:

ºC

Return:

ºC

Circuit No. 4:

Flow:

ºC

Return:

ºC

Circuit No. 5:

Flow:

ºC

Return:

ºC

Circuit No. 1:

Flow:

ºC

Return:

ºC

Circuit No. 2:

Flow:

ºC

Return:

ºC

Circuit No. 3:

Flow:

ºC

Return:

ºC

Circuit No. 4:

Flow:

ºC

Return:

ºC

Circuit No. 5:

Flow:

ºC

Return:

ºC

Manifold No. 2:


109

B

APPENDIX

Manifold No. 3:

2.10

Circuit No. 1:

Flow:

ºC

Return:

ºC

Circuit No. 2:

Flow:

ºC

Return:

ºC

Circuit No. 3:

Flow:

ºC

Return:

ºC

Circuit No. 4:

Flow:

ºC

Return:

ºC

Circuit No. 5:

Flow:

ºC

Return:

ºC

What are the circuit flow rates? Manifold No. 1: Circuit No. 1:

l/min

Circuit No. 2:

l/min

Circuit No. 3:

l/min

Circuit No. 4:

l/min

Circuit No. 5:

l/min

Manifold No. 2: Circuit No. 1:

l/min

Circuit No. 2:

l/min

Circuit No. 3:

l/min

Circuit No. 4:

l/min

Circuit No. 5:

l/min

Manifold No. 3:

2.11

110

Circuit No. 1:

l/min

Circuit No. 2:

l/min

Circuit No. 3:

l/min

Circuit No. 4:

l/min

Circuit No. 5:

l/min

What are the floor surface temperatures? Room 1:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 2:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 3:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 4:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 5:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 6:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 7:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 8:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 9:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

Room 10:

Max. temp.

ºC

Min. temp.

ºC

Ave. temp.

ºC

2.12

Have the manifolds/circuits been commissioned?

Yes

2.13

Have commissioning sheets been provided?

Yes

No

2.14

Do the above readings match the design figures?

Yes

No

2.15

Do the commissioning readings match the design figures?

Yes

No


No

B

APPENDIX

2.16

What are the room air temperatures? Room 1:

ºC

Room 2:

ºC

Room 3:

ºC

Room 4:

ºC

Room 5:

ºC

Room 6:

ºC

Room 7:

ºC

Room 8:

ºC

Room 9:

ºC

Room 10:

ºC

2.17

Is any remedial work required to the installation?

Yes

No

2.18

Have record drawings, reflecting any site variations, been completed?

Yes

No

2.19

If so, have the record drawings been submitted?

Yes

No

Comments:


111

C

APPENDIX

APPENDIX C: 2010 BUILDING REGULATIONS The following information is extracted verbatim from the [11] Domestic Building Services Compliance Guide 2010 , Section 7, Table 27 (1-3) and Table 30.

112

Floor insulation and design for reducing distribution losses

Minimum provision

1 Exposed ground floors

a. Ground floors on earth, or suspended floors in contact with outside air, should be insulated to limit downward heat loss to 2 not more than 10 W/m resulting from thermal resistance of the applied floor finish. b. When heat output is not known, but the floor finish is specified, the extra amount of system thermal insulation may be calculated using the sum of the thermal resistance of the floor finish and the thermal resistance of the underlying heated layer, all multiplied by a factor of 10. c. Supplementary floor heating system thermal insulation may be supplied independently, or added to the statutory insulation requirement. d. Floor heating systems intended for cyclical operation or installed over unheated rooms should be separated from the structural floor by a layer of thermal insulation of at least 2 1·25 m K/W thermal resistance, and installed below the heated plane.

2a Intermediate floors with heated rooms below: wet systems

a. Intermediate floors with heated rooms below complying with both. Part L and Part E of the Building Regulations, should have a separating layer of system thermal insulation to comply with either 1b above or BS EN1264 Part 4, where the minimum 2 thermal resistance is given as not less than R = 0·75 m K/W.

2b Intermediate floors with heated rooms below: electric systems

a. Intermediate floors with heated rooms below complying with both Part L and Part E of the Building Regulations, should have a separating layer of system thermal insulation where the minimum 2 thermal resistance is not less than R = 0·5 m k/W, or comply with 1b above

3 System design to minimise distribution losses

a. Underfloor heating distribution boards or warm water distribution manifolds should be located centrally between the rooms being heated, thus minimising the length of interconnecting services. b. Service pipes carrying hot water to more distant rooms should be insulated or routed through conduits to reduce distribution losses and the risk of overheating the room or floor finish.

Underfloor heating

Minimum provision

Supplementary information

5 System commissioning and corrosion protection Control of oxidation, biofilm, scale and sludge in warm water heating system

a. Commissioning warm water floor heating systems should be carried out in accordance with BS EN 1264 Part 4. Even where plastic tubes contain oxygen gas barriers, the control of corrosion in mixed product heating systems must be addressed carefully. b. After testing and flushing with clean water, the system circulating fluid should be treated with a suitable corrosion inhibitor approved by the tube manufacturer and complying with BS 7593:2006 or DIN 4725/6, and applied strictly in accordance with the additive manufacturer’s instructions.

BS 7593:2006 Code of Practice for Treatment of Water in Domestic Hot Water Central Heating Systems. Inhibitors should as a minimum be BuildCert approved. Note should also be made of advice in the manufacturer’s instructions.


Supplementary information

Thermal insulation of party floors is essential because the floor or ceiling is directly coupled to the heating elements.

APPENDIX

D

APPENDIX D: ESTIMATING COOLING CAPACITY If the surface temperature, flow temperature and corresponding heat output of the underfloor system in heating mode is known then it is straightforward to make an estimate of the potential cooling output. First, the total resistance to heat flow is the sum of the resistances of the floor elements and covering plus the surface resistance. The surface resistance is the inverse of the surface heat transfer coefficient (11·0 2 W/m K for heating): R HEAT = R STRUCTURE + R COVER +

1 11·0

The same equation applies to cooling but with a different surface heat 2 transfer coefficient (6·7 W/m K for cooling): R COOL = RSTRUCTURE + R COVER +

1 6·7

Therefore: R COOL = R HEAT + 0·058

Since the heat output is the overall temperature difference divided by overall resistance: q HEAT =

ΔTHEAT R HEAT

Similarly, for cooling then:

qCOOL =

ΔTCOOL ΔTCOOL ΔTCOOL = = (RHEAT + 0·058) ⎛⎜ ΔTHEAT RCOOL ⎞ + 0·058 ⎟⎟ ⎜ q ⎝ HEAT ⎠ 2

As an example, suppose a floor produces 70 W/m with a mean water temperature of 38°C. Assuming the indoor temperature is 20°C gives ΔTHEAT= 18°C. If we assume that the cooling is activated for temperatures above 28°C for a mean cooling water temperature of 16°C then ΔTCOOL= 12°C. The corresponding cooling output from the above equation is then: q COOL =

12 ⎞ ⎛ 18 + 0·058 ⎟ ⎜ ⎠ ⎝ 70

= 38 W/m

2


113

D

APPENDIX

Before proceeding further, it is necessary to check the condensation risk by calculating the floor surface temperature. That is simply calculated from:

ts = ta −

qcool 38 = 28 − = 22·3 °C 6·7 6·7

As dewpoints in the UK are rarely above 20°C the condensation risk is negligible. This is not enough to calculate the cooling effect accurately in terms of the operative temperature, since that depends on knowledge of the internal heat gains, ventilation rates and external air temperature. It does, however, put a limit on the lowest temperature that can be achieved in the space, since that cannot be less than the floor surface temperature.

114


REFERENCES

REFERENCES 1

BS EN 1264-3:2009 Water Based Surface Embedded Heating and Cooling Systems. Dimensioning.

2

BS EN ISO 7730: 2005 Ergonomics of the Thermal Environment. Analytical Determination and Interpretation of Thermal Comfort using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria.

3

BS 7291-3:2010 Thermoplastics Pipe and Fitting Systems for Hot and Cold Water for Domestic Purposes and Heating Installations in Buildings. Specification for Crosslinked Polyethylene (PE-X) Pipes and Associated Fittings.

4

BS EN 15875-2:2003 Plastics Piping Systems for Hot and Cold Water Installations. Crosslinked Polyethylene (PE-X). Pipes.

5

BS 7291-2: 2010 Thermoplastics Pipe and Fitting Systems for Hot and Cold Water for Domestic Purposes and Heating Installations in Buildings. Specification for Polybutylene (PB) Pipe and Associated Fittings.

6

BS EN ISO 15876-2:2003 Plastics Piping Systems for Hot and Cold Water Installations. Polybutylene (PB). Pipes.

7

DIN 4726:2000 Warm Water Floor Heating Systems and Radiator Pipe Connecting - Piping of Plastic Materials.

8

BS EN ISO 22391-1:2009 Plastics Piping Systems for Hot and Cold Water Installations. Polyethylene of Raised Temperature Resistance (PE-RT). General.

9

DIN 4724:2001 Plastic Piping Systems for Warm Water Floor Heating Systems and Radiator Pipe Connecting – Cross-Linked Polyethylene of Medium Density (PE-MDX).

10

BS EN 1254-4:1998 Copper and Copper Alloys. Plumbing Fittings. Fittings Combining Other End Connections with Capillary or Compression Ends.

11

Domestic Building Services Compliance Guide 2010 (for the Building Regulations).

12

BS EN 1264-4:2009 Water Based Surface Embedded Heating and Cooling Systems. Installation.

13

BSRIA Screeds with Underfloor Heating – Guidance for a Defective-Free Interface, Co-Construct, , IEP 11/2003. ISBN 0 80622 627 1.

14

BS EN 1264-1:1998: Floor Heating - Systems and Components. Definitions and Symbols.

15

BS EN 1264-2:2008: Water Based Surface Embedded Heating and Cooling Systems. Floor Heating. Prove Methods for the Determination of the Thermal Output using Calculation and Test Methods.

16

BS EN 1264-5:2008 Water Based Surface Embedded Heating and Cooling Systems. Heating and Cooling Surfaces Embedded in Floors, Ceilings and Walls. Determination of the Thermal Output.

17

BS EN 15377-1:2008 Heating Systems in Buildings. Design of Embedded Water Based Surface Heating and Cooling Systems - Determination of the Design Heating and Cooling Capacity. UNDERFLOOR HEATING AND COOLING © BSRIA BG 4/2011

115

REFERENCES

116

18

BS EN 12831:2003 Heating Systems in Buildings. Method for Calculation of the Design Heat Load. Annex A and Annex B.

19

CIBSE Guide A. Environmental Design. 2006. ISBN: 1903287669.

20

British Council for Offices Guide to Specifications 2009. Best Practice in the Specification for Offices.

21

Building Regulations (Approved Documents L1A and L2A).

22

Building Regulations Part L Simplified Building Energy Model (SBEM), (Software).

23

BS EN 15450:2007 Heating Systems in Buildings - Design of Heat Pump Heating Systems.

24

BS EN 15377:2008 Heating systems in buildings. Design of Embedded Water Based Surface Heating and Cooling Systems.

25

CIBSE Underfloor Heating Design and Installation Guide, 2004, ISBN 1903287464.

26

BSRIA, Whole-Life Costing Analysis, BG 5/2008. ISBN 978 086022 676 5.

27

BS EN 15450: 2007 Heating systems in buildings. Design of Heat Pump Heating Systems.

28

BS 8204-1:2003+A3:2009 Screeds, Bases and in-situ Floorings. Concrete Bases and Cementitious Levelling Screeds to Receive Floorings. Code of Practice.

29

BS 8204-2:2003+A1:2009 Screeds, Bases and in situ Floorings. Concrete Wearing Surfaces. Code of Practice.

30

BS 8204-3:2004+A1:2009 Screeds, Bases and in situ Floorings. Polymer Modified Cementitious Levelling Screeds and Wearing Screeds. Code of Practice.

31

BS 8204-4:2004 Screeds, Bases and in situ Floorings. Cementitious Terrazo Wearing Surfaces. Code of Practice.

32

BS 8204-7:2003 Screeds, Bases and in-situ Floorings. Pumpable Self-Smoothing Screeds. Code of Practice.

33

BS 5385-3:2007 Wall and Floor Tiling. Design and Installation of Internal and External Ceramic Floor Tiles and Mosaics in Normal Conditions. Code of Practice.

34

BS EN ISO 10545-8:1996 Ceramic Tiles. Determination of Linear Thermal Expansion.

35

BS 8201:1987 Code of Practice for Flooring of Timber, Timber Products and Wood Based Panel Products.

36

Health and Safety at Work etc Act 1974.

37

The Construction (Design and Management) Regulations 2007, SI No. 320.

38

The Management of Health and Safety at Work and Fire Precautions (Workplace) (Amendment) Regulations 2003. SI No. 2457.

39

Personal Protective Equipment at Work Regulations 1992. SI No. 2966.


REFERENCES

40

Electricity at Work Regulations 1989. SI No. 635.

41

The Manual Handling Operations Regulations 1992. SI No. 2793.

42

The Provision and Use of Work Equipment Regulations 1998. SI No. 2306.

43

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995. SI No. 3163.

44

BSRIA, A Design Framework for Building Services – Design Activities and Drawing Definitions. BG 6/2009. ISBN 978 086022 878 9.

45

BSRIA, Pre-Commission Cleaning of Pipework Systems AG 1/2001.1. (2004) 2 edition. ISBN 086022 644 1.

46

BS 7671:2008 Requirements for Electrical Installations. IEE Wiring Regulations. Seventeenth edition.

47

Part P of the Building Regulations.

48

BSRIA, Handover, O&M Manuals and Project Feedback - A Toolkit for Designers and Contractors. BG 1/2007. ISBN 978 086022 667 3.

nd


117

BEAMA

UHMA advert

14/12/10

12:00

Page 1

Underfloor heating – the intelligent green choice for heating Britain’s buildings.

Whatever the heat source – be it heat pump, biomass boiler or conventional condensing boiler – one thing is certain; systems now have to function efficiently at lower temperatures. Suitable for both residential and non residential applications underfloor heating offers a practical and highly efficient method of heat distribution that is unique in its ability to offer an even level of heat in the room.

UHMA is the trade association for all forms of radiant heating, promoting the highest standards for materials used, system design and application. Our members specialise in the design and supply of UFH systems and components helping specifiers get the right solution for their project.

For reliable advice talk to an UHMA member

www.uhma.org.uk or call 020 7793 3000

Project1_Layout 1 16/12/2010 15:54 Page 1

Underfloor cover:D3-2010 Legislation cover.qxd 13/12/2010 10:55 Page 2

BSRIA ⳮ the built environment experts BSRIA gives you confidence in design, added value in manufacture, competitive advantage in marketing, profitable construction, and efficient buildings

Whatever your building services requirement contact BSRIA: T: +44 (0)1344 465600 F: +44 (0)1344 465626 E: [email protected] W: www.bsria.co.uk

Old Bracknell Lane West, Bracknell, Berkshire, RG12 7AH, UK Offices in Bracknell, Beijing, Dunfermline, Madrid, North America, St Helens, and Toulouse. Associates in Armagh and Cadiz

¢ Testing

¢ Troubleshooting

¢ Modelling

¢ Information

¢ Research

¢ Training

¢ Consultancy

¢ Publications

¢ Instrument hire,

¢ Market research and

sales and calibration

intelligence

Membership is the foundation of BSRIA’s expertise and independence

Underfloor Heating and Cooling

Recommend Documents