BHATSHALA HOUSE CASE STUDY

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BHATSHALA

HOUSE

ARCHITECTS VILLAGE HOME AT

BRAHMANBARIA , BANGLADESH

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

sajib71@yahoo.com.

OWNER :

ARCHITECTS FAMILY

ARCHITECT:

BASHIRUL HUQ

PROJECT INITIATION :

FEB 1989

PROJ. COMPLETION :

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 L-

shaped 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

bearing structure on the ground floor which continues up until a portion of the 1st 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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5

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8

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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

3 PM

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9AM

12 PM

3PM

SHADOW STUDY AT 9TH SEPTEMBER

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9AM

12 PM

3 PM

Perspective shadow study from the court at 9th September

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9th September Corridor temperature analysis, Ground Floor

9th September Bed Room temperature analysis, Ground Floor

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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 Living Room temperature analysis, Ground Floor

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

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 .

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10th June Corridor temperature analysis ground floor

10th June Living Room temperature analysis ground floor

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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.

10th June Bedroom temperature analysis, 1st floor

10th June Corridor temperature analysis . 1st Floor

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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

3 PM

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8th January Corridor temperature analysis . Ground Floor

8th January Living room temperature analysis, Ground Floor

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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.

8th January Bedroom temperature analysis. 1st Floor

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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 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.

10th October Bedroom temperature analysis, 1st Floor

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15TH JUNE RADIANT TEMPERATURE AT GROUND LEVEL

8AM

12 PM

4PM

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8AM

12PM

3PM

SHADOW STUDY AT 15TH JUNE

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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.

15th June Corridor temperature analysis, Ground floor

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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.

at 3’

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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.