BHATSHALA HOUSE CASE STUDY
BHATSHALA HOUSE ARCHITECTS VILLAGE HOME AT BRAHMANBARIA , BANGLADESH
OWNER : ARCHITECTS FAMILY
ARCHITECT: BASHIRUL HUQ PROJECT INITIATION : FEB 1989 PROJ. COMPLETION :
SUMMARY: Bhatshala House within the grandiose entities of Brahmanbaria is a fine example of responsive architecture and its relative synthesis with the surrounding dimensions. Weather analysis and its effects on the existing structure depicts the successful evaluation of proper comfort zones in relation to the local climatic contexts. To understand the spatial climate variables within and outside the structure, AUTODESK ECOTECT and weather data file from USGS has been used Tawhid Mustafa
[email protected].
DEC 1989 TOTAL BUILT AREA : 1592 SFT COST : TK 395,000
KEYWORDS: indoor environment, thermal building simulation, solar study, Prevailing Wind simulation, relative connection.
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1. Introduction Bhatshala House, a spec of crimson shade in the midst of serene rural fields, in other words the village residence of Architect Bashirul Haq, while blending in spontaneously with its context is an ingenious example of ecofriendly vernacular architecture. An uthan (courtyard) is semi enclosed on its north and western borders by facades of sun baked bricks which reflects the traditional approach in local homesteads forming around a courtyard. The existing plinth forms an Lshaped base negotiating with the arched columns formed of bricks supporting the R.C.C roof. Immediately following the arched columns is the corridor in common with the primary functions of the house. This circulation space acts as a thermal buffer in the preceding rooms. The diffuse character of the plan makes the indoor environments react comfortably with the humid climates outside (further explained in Interior/Exterior temperature analysis).This has been further accentuated by having wooden louvered windows and doors alongside the rooms. Situated in the Brahmanbaria district this place lies in the east central region of Bangladesh at 23°53'49.25"N, 91°10'5.29"E. The geography of the
district is characterized by low-lying land with small hills and hillocks of red soil. Annual highest average temperature is 34.3 °C and lowest 12.7 °C. Total annual rainfall is around 2551 mm.
2. Description of the building construction
The building has exposed brick facades with a combination of arched and rectangular linear openings. It is a load st bearing structure on the ground floor which continues up until a portion of the 1 floor. The load bearing walls are primarily laid by Flemish bonds with reinforcement at regular intervals. The first floor is quite diffused in nature which is shaded relatively with Corrugated sheets resting on wooden piers or structure . The gabled sheets form an angle of 25 deg with the horizontal axis. Reinforcements are provided which runs through rcc slabs to the brick walls over which the wooden piers are bolted on.
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3. Analyzing the thermal conditions
As the weather data for for Brahmanbaria is not yet (as of 2012) available, datas from weather stations at Dhaka Tejgaon has been used due to its relatively closer distance then other stations DHAKA/TEJGAON_(MIL) , BGD . The data file is used to retrieve local variables for solar radiation, wind speed, rain and air pressure and temperature with the help of WEATHER TOOL (ECOTECT). As this analysis report resorts to simulation results there are some unpredictable deviations which should be accounted for in formulating an assumption.
In order to get additional information like influence of thermal buffers, materials, wind vortex etc whole building simulations were carried out. For the simulation of the thermal behavior the software tool AUTODESK ECOTECT is used. The building is separated into several zones with a perfect air exchange along most of the openings. The corridor has been accounted as a separate thermal zone as this affects the consecutive rooms in a significant manner.
Charts on the following page depicts respective climatic variable in the existing surroundings.
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From the chart some days in particular can be retrieved which provides a satisfactory timeframe for running the simulation, which mentioned below-
Hottest Day (Peak):
9th September
Hottest Day (AVG) :
10th June
Coldest Day (Peak):
8th January
Coldest Day (AVG):
8th January
Brightest Sunny Day:
10th October
Most Overcast Day
15th June
:
Strongest Wind Gust:
17th February
Least Windy Day
14th January
:
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SIMULATION RESULTS Hottest Day (Peak):
PAGE 11
Hottest Day (AVG) :
PAGE 16
Coldest Day (Peak):
PAGE 21
Brightest Sunny Day: PAGE 26 Most Overcast Day
: PAGE 30
Strongest Wind Gust: PAGE 33 Wind Simulation
: PAGE 35
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9th SEPTEMBER RADIANT TEMPERATURE AT GROUND LEVEL
9 AM
12 PM
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3 PM
9AM
12 PM
3PM
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SHADOW STUDY AT 9TH SEPTEMBER
9AM
12 PM
3 PM
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Perspective shadow study from the court at 9th September
9th September Corridor temperature analysis, Ground Floor
9th September Bed Room temperature analysis, Ground Floor
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9th September Living Room temperature analysis, Ground Floor
There is a rise in temperature on the living room in morning compared to the Bedroom and corridor because of the eastern exposure accentuated by glare from the court.
9th September Bedroom temperature analysis, 1st Floor
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10TH JUNE RADIANT TEMPERATURE AT GROUND LEVEL
9AM
12 PM
3 PM The stair room helps to absorb a substantial amount of heat thus keeping the Bedroom temperature lower.
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7AM
12 PM
3:30PM SHADOW STUDY AT 10TH JUNE
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8 AM
12 PM
3:30 PM Perspective shadow study from the court and Northern side at 10th June
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It has to be noted at June the azimuth angle of sun reaches 65.5 deg to -65.7 deg therefore illuminating the northern facades .
10th June Corridor temperature analysis ground floor
10th June Living Room temperature analysis ground floor
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10th June Corridor temperature analysis . 1st Floor
10th June Bedroom temperature analysis, 1st floor
At 10th june the sun reaches a northerly tilt as it travels down the horizon, therefore the living room receives greater radiation in the morning , causing an increase in temperature.
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8TH JANUARY RADIANT TEMPERATURE AT GROUND LEVEL
9AM
3PM
10PM
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9AM
12 PM
3 PM SHADOW STUDY AT 8TH JANUARY
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9 am
12 PM
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3 PM
8th January Corridor temperature analysis . Ground Floor
8th January Living room temperature analysis, Ground Floor
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8th January Bedroom temperature analysis. 1st Floor
According to the radiant temperature simulation, the corridor plays a significant part in winter affecting the surrounding rooms conserve its energy. At night the ground floor living room and Bedroom stays warmer than the corridor (page 20, 10pm), and in the morning the reverse is observed.
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10TH OCTOBER RADIANT TEMPERATURE AT GROUND LEVEL
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9AM
12PM
3PM SHADOW STUDY AT 10TH OCTOBER
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10th October Corridor temperature analysis, Ground Floor
10th October Living Room temperature analysis, Ground Floor
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10th October Bedroom temperature analysis, 1st Floor
10th October is statistically the brightest day on average (weather data file , Dhaka/TEJGAON) during this time the 1st floor bedroom receives the most radiation, consecutively wind simulation (pg. 37) shows funneling around the corner of this bedroom therefore the cool off after 1:30 PM.
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15TH JUNE RADIANT TEMPERATURE AT GROUND LEVEL
8AM
12 PM
4PM
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8AM
12PM
3PM
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SHADOW STUDY AT 15TH JUNE
15th June Corridor temperature analysis, Ground floor
On june the sun reaches a rare phenomenon on this country as it reaches a northerly tilt as it attempts the horizon, the corridor at this time is mostly shaded and with the prevailing winds is becomes significantly cooler. This corridor acts a buffer for affecting the temperature of other rooms.
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17 FEBRUARY RADIANT TEMPERATURE AT GROUND LEVEL
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17th February Corridor temperature analysis, ground floor
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Wind data shows there is a strong south easterly wind during the month of June therefore a simulation is done using June/July data with an average speed of 1.2 to 8 m/s which is shown below.
at 1’6”
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at 3’
at 11’
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at 16’
Wind data shows at the ground floor there is a funneling around the north western side of the house pulling in the southern winds through the corridor.
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During winter the wind vector changes from south to north, therefore in January there is a northerly wind at random intervals, a simulation is run with a speed of .5 to 4 m/s at this time.
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at 3’
at 16’
Diagram showing the funneling created at the first floor which travels out through the bedroom
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CONCLUSION: It has to be noted that there are inaccuracies due to the slight shift in geographic location from where the weather data file are indexed. Still regardless of the deviations some very interesting phenomena is observed in this hypothetical simulation. Such as the corridor acting as thermal buffer during the month of October (hot) and January (cold). In January the living room stays warmer accentuated by the corridor. The stair room also help to reduce a major portion of radiant heat from reaching the bedrooms. During the month of June, as the sun reaches an azimuth angle of 65° the living room receives greater radiation during the morning while rapidly cooling off after 12 PM, compared to the outside temperature. Most of the rooms are relatively cooler then outside temperature during day time and warmer during the night. The uthan (courtyard) does seem to radiate substantial glare at morning thus increasing the temperature of the living room when the sun travels from east to south azimuth angles. Although this happens in a relatively lesser frequency, the actual site has substantial vegetation coverage to reduce this glare. This wasn’t accounted in this simulation. In summer time when there is a slight south easterly wind it funnels in through the corridor beside ground floor living room and Bedroom. There some random gusts generated from the north western side which travels back and forth through the main corridors.
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