Sangath and passive solar hstl by bv doshi

SANGATH

An architect’s studio, Ahmedabad

BV Doshi

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.

Design features Sandwiched construction of vault

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

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.

The ventilating window at upper volume releases the accumulated hot air through pressure differences.

Envelope design

Subterranean spaces

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).

Passive solar design 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

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.

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.

Performance

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.

SOLAR PASSIVE HOSTEL, JODHPUR

Climatic Zone: Hot and Dry

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.

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.

Materials and methods of construction

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.

Passive solar design 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.

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.

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.

Window design

Since the university is normally on vacation during the worst summer months, winter comfort is as important as summer comfort. South-facing 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.

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.

Conclusion

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.