sangath and the passive solar hostel built and designed by bv doshi

1. An architect’s studio, Ahmedabad
BV Doshi

2. General description
The relative organization of form elements, layering of spaces,
controlled interiors and transitions to the outside, the
interruption of the skyline through varying outlines that break
the sun into shadow, and open the roof into the night sky, are
themes that respond well to the hot and arid climates.
 At Sangath, the architect’s design studio, these responses are
at their best. The architectural studio comprising reception
areas, a design studio, office spaces, workshop, library,
conference room, and other ancillary spaces has been
designed to naturally manage the forces of nature. There are
spatial, constructional, and landscape responses to combat the
vagaries of nature in the hot dry climate. In Ahmedabad, the
summer temperature reaches 45 °C and the heat is very
intense. It is the heat rather than the breeze that becomes
critical. Natural comfort conditions can be achieved by
protecting spaces from the heat and glare of the sun.


4. Design features
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Sandwiched construction of vault
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The vaulted roof is of locally-made clay fuses over the
concrete slab, which provides a non-conducting layer. The
top finish of China mosaic glazed tiles further adds to the
insulation. Being white and glossy it reflects sun while being
made from clay it retards the heat transmission.
Vaulted roof form
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The roof form creates an efficient surface/volume ratio
optimizing material quantities. The higher space volume thus
created provides for hot air pockets due to convective
currents that keep lower volumes relatively cool.
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The ventilating window at upper volume releases the
accumulated hot air through pressure differences.

5. 
Envelope design
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Subterranean spaces
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The building is largely buried under the ground to
use earth masses for natural insulation.
Storage walls
External walls of the building are nearly a metre
deep but have been hollowed out as alcoves to
provide storage that becomes an insulative wall
with efficiency of space (for storage functions).

7. Passive solar design
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Indirect/diffused light
Sun light brings heat and haze with it. To maximize daylight
(intensity of illumination) and to diffuse heat and glare, the light
is received in indirect manner by diffusing it. There are three
ways by which natural light is drawn within.

By upper-level large openings towards north direction, which is
cool, and consistent light is reflected off the clouds

Skylights, which are projected masses from the roof, reflect the
light on the white inner wall surface, which further radiates light
into the room

Innermost spaces are lit up through small cutouts in the roof
slab, which are then filled with hollow glass blocks that take
away the glare and transmit diffused light

9. Landscaping

Microclimate through vegetation

Lawns and vegetative cover all around create a
favourable microclimate by absorbing solar radiation and
providing a cooler passage of air through humidity.

Water channels
Rainwater and overflow of pumped water from the roof
tank are harnessed through roof channels that run
through a series of cascading tanks and water channels
to finally culminate in a pond from where it is recycled
back or used for irrigating vegetation.
 Water cascades also provide interesting visual
experiences.


11. Materials and methods of
construction

Exposed natural finishes

The concrete of slabs and wall surfaces are kept bare
unplastered as final visual finishes, which provide a natural look
and save on finishing material quantity.

Use of secondary waste material

Paving material is a stone chip waste while the roof surface is
glazed tiles waste, both available as waste material from
factories at no cost. These have been creatively hand-crafted
and integrated into the design by fully using waste material.

The application is also skill-oriented and involves as well as
promotes craftsmen and our traditional heritage.

13. 
Performance
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The above measures have ensured excellent climate control in
terms of keeping the inside cool and increasing the time-lag for heat
transfer.

There is a difference of about 8 oC between the interior and exterior
roof skin temperatures. The time-lag for heat transfer is nearly six
hours.

The natural elements are harmoniously blended with the built
environment, and water recycling and waste material reuse have
ensured cost economy as well as environmental consciousness.

14. Climatic Zone: Hot and Dry

15. General description

The solar hostel was put up as part of
the research project undertaken by the
Centre of Energy Studies, Indian
Institute of Technology, Delhi. Although
energy conservation was stated as the
objective, the design attempted to test
and demonstrate suitable methods of
providing thermal comfort in the hot and
dry climate of Rajasthan.

17. Architectural design
The building had to be designed to house 14 double room
suites for married students.
 The two-storeyed building has seven suites on the ground
floor and seven suites on the first floor. Each suite is
provided with a toilet (about 4 m² floor area), one lobby,
and a small courtyard.
 The ground floor that has seven double rooms is partially
sunk into the ground to take advantage of the earth’s
thermal storage and insulation effect.
 The wind tower, erected over the lobby of the first floor, is
connected to the ground floor through the staircase and
supplies cool air to the seven units. The hot room air exits
by means of smaller chimneys over each room.


18. Materials and methods of
construction
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The protection of the roof and its treatment is important because it is a major source
of summer heat gain. The roof has been insulated by providing small inverted
terracotta pots over the stone slabs and filling up the intervening spaces with lime
concrete.
Stone masonry has been used for walls because it is a local material and can
provide good thermal mass to balance out diurnal temperature variations. The wall
thickness varies from 0.30 m to 0.45 m.
The wind tower helps to ventilate the heat out of the room during late evenings and
nights.
The design of the building has a set of rooms partially underground. This did not
pose any major construction problems in Jodhpur because of its low water level.
Toilets were also placed at the same level as these can be drained to the sewage
system or decomposition tank/pit as the case may be. The partially underground
configuration has a moderating influence on the temperatures, reducing the solar
heat gain on the walls and cooling like a basement.
For this building, an improved design of wind tower was made with built-in
evaporative cooling to lower temperatures. The higher rates of airflow and the
evaporative capacity of the new wind tower can be fully utilized at night in summer to
cool the building mass to lower temperatures.

19. Passive solar design
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The air being very dry, evaporative cooling in
summer can prove to be very effective in Jodhpur.
Unfortunately, as water is a scarce commodity in
summer in Jodhpur, any system that depends upon
water for cooling is bound to fail.
The design, therefore, uses a favourable orientation,
a massive structure, and an air gap in the roof for
insulation, reflective external finishes, deep
sunshades, and finally a wind tower for making use
of the cool winds. An experimental evaporative
cooling system using wires for water distribution has
also been installed on the wind tower.

20. Wind tower

The prevailing direction for cool winds in Jodhpur is
the south-west. Window apertures are difficult to
provide in this orientation, as it is the least favourable
from the point of view of solar radiation.

To overcome this problem, a wind tower concept was
used. The tower facing the wind direction has been
located over the staircase, thus minimizing costs.
Cool air is provided to each room from this tower and
normal windows or smaller shafts (towers) facing the
lee of the wind have been provided to distribute the
cool air throughout the building. The tower catches
only the cool wind from the south-west, avoiding
warmer air from other directions.

22. 
Roof insulation
The most commonly used building material in Jodhpur is stone
sourced locally. Blocks of this light-coloured stone have been used for
walls in the building. Large slabs of stone have been used for the
roofing, staircases, partitions, and lintels over windows.
 The roof has been insulated by providing small inverted terracotta pots
over the stone slabs and filling up the intervening spaces with lime
concrete. Since very few manufactured materials have been used, this
is a low embodied energy building.

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Window design
Since the university is normally on vacation during the worst summer
months, winter comfort is as important as summer comfort. Southfacing windows have been provided in most of the rooms.
 To prevent heat loss during night, solid timber shutters have been
provided in addition to glass ones.


23. Performance
 The results of monitoring in various
rooms of the hostel show that internal
temperature remains nearly constant
around the day without much fluctuation
on a typical summer and winter day,
while the ambient temperature has a
large diurnal variation.

24. Conclusion
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Favourable orientation
Low embodied energy by making minimal use of
manufactured materials
Heavy construction to balance out diurnal temperature
variation
Roof insulation by air gap
Light-coloured building to reflect heat
Wind tower with evaporative cooling for summer cooling
Building partially sunken to moderate internal temperature
South-facing window with deep sunshades to cut off
summer sun and to let in winter sun
Solid timber shutters in addition to glass shutters to
prevent heat loss during winter nights.