Careful siting
Half the battle for comfort against the vagaries of climate in a city such as Delhi is often won by orienting the building sensibly with respect to the sun.

Prakash has provided a continuous veranda and roof overhangs towards the south (the entrance facade) so that the external walls are always in shade and absorb less heat. To the north he deftly integrated a vertical "fin" (a bit of wall extending out of the building) to cut off the low but harsh summer morning and evening sun which would otherwise heat up the north walls. In both cases, the heat that the external walls soak up and radiate inwards is thus reduced significantly in spite of the dark colour of the exposed brick.

The roofs
Since almost 70% of the heat a building absorbs comes through the roof, these are either covered with highly reflective white broken tiles or are insulated in two ways. The almost 15-inch-thick vaulted brick roof of the upper floor bedrooms insulates largely with its very thickness, and is covered with light insulation waterproofing and a white broken tile finish. The flat slab over the dining room has a lawn growing on it for insulation.

Air-conditioning strategies
The basic principle Prakash followed was to reduce the demand for cooling by reducing the heat absorption of the house. Given the dry local climate, he decided to use an air cooler (environmentally more benign) for the spacious living-dining area, while centrally air conditioning the rest of the house. Finally, the desired temperature that the central chilled water air conditioning system is set to achieve is higher than normal at 28 degrees.

The centralized system also has a good storage capacity for chilled water.

The water is stored at the highest possible temperature so as to be produced and stored efficiently. The room units are set to deliver more air than conventional air conditioning, in order to respond to the higher setting for water and indoor temperature. Coupled with a lifestyle adjustment in clothes and diet, a significant saving in energy consumption is achieved even as interior space is comfortably cooled in summer.

Prakash has provided an 80,000-litre underground tank to harvest rainwater. A gift of the sky and extremely pure, this filtered rainwater is fed to the washing machine, dishwasher, the air-cooler and the air-conditioning system. The tank is built of brick masonry instead of reinforced concrete which makes it much cheaper (at less than Rs2 per litre) at half to one-third the normal cost. Masonry construction is also less energy intensive.

Finishes
The external surfaces of the secondgrade brick walls are left exposed, which looks good; it also avoids the use of cement in plaster. Internal wall surfaces are plastered because they can be painted white to maximize reflection of natural light all over the house and help reduce electricity consumption for lighting. Bathroom walls, too, are putty-textured and the use of tiles restricted to wet areas.

Much waste finishing material was reused, partly by designing floors and bathroom patterns at the end of the construction process. Pieces of stone from the kitchen and washbasin counters have been integrated into bands in the flooring pattern. Prakash has even gone to the extent of reusing leftover copper pipes from the air-conditioning system to making water spouts in the washbasin of the guest bathroom.

Flooring
Not only fashionable, but also sustainable, is the "wooden" floor for the children's rooms that Prakash has provided. Only, it is not wood, but bamboo, in an arrangement that looks like planking. This floor is composed of prefabricated panels--made by sticking together thin layers of bamboo--that are placed but not stuck to the floor by wedging them under the skirting.

Like the doors in the house (of mango wood), and the sandstone slabs in part of the roof, this floor can also be "reclaimed" entirely, for reuse or resale. Given the volatile real estate market, this may well become a reality.