Text: Himanshu Burte
We expect relatively sustainable buildings to look ‘different’. Khadke house (4000 square feet,six bedrooms), designed by Girish Doshi for Pune’s composite climate with its hot-dry summers, looks like any other elegant contemporary house designed by a very skilled architect. Built for a joint family that had earlier lived in a traditional wada in the old heart of Pune, it is designed like a wada but also has the usual modernist characteristics- white walls (inside and out), a simple cuboidal form, and the very contemporary accent of polished wooden elements in windows and related elements. These are not automatic markers of sustainable form. And yet, this building is actually much more sustainable than most others.
There are two innovations at work in the house. One is related to construction technique that saves energy intensive materials in the masonry and RCC work. Another is about inducing ventilation using wind towers.
Since the 1980s Doshi has perfected an innovative system of construction first developed by V. D. Joshi, a structural engineer who has collaborated with the eminent Ahmedabad architect, B. V. Doshi on many of his important projects. Khadke house has load-bearing hollow concrete block walls, with RCC stiffening columns with nominal steel at corners for earthquake resistance. Floor and roof slabs have two parts: the top 2 inch thick layer is a ferrocement slab, while the lower layer is 6 inch thick hollow concrete block. Beams are absorbed within the 8 inch thickness of the slab which ensures that there are no projections inside or outside.
The construction system has dual benefits. It saves a lot of cement and steel, and with its hollows, it also provides insulation from the outside heat. The absence of projections that this system allows is perfectly in tune with the value placed on smooth uninterrupted surfaces and forms in the modernist aesthetic that Doshi works with.
While the construction system is something Doshi has used for a long time, he has recently started integrating wind towers along with other passive devices for ventilation into his designs where possible and appropriate.
Khadke house has four wind towers that catch breeze at a height and channel it down into different spaces. These towers have provisions for fountains at their base which would humidify (and cool) the incoming breeze before it blows into the adjacent spaces. The house plan is organized around a double height atrium whose glass roof strip is flanked by towers that have extractor fans activated by the natural upward movement of hot air. A good draft develops in the house since cool air from the wind towers comes into the interior space, gets heated up and rises up through the atrium. The greater the temperature difference between inside and outside, the stronger this cycle gets.
Doshi has also reexamined window design and has done away with glass in shutters. He has developed a low cill, two part (upper-lower), multilayered window detail with shutters in solid wood. The upper part of the window (starting at waist height) has no grill and can be kept open by day when the room is occupied by day. The lower part of the window has one external layer of wooden shutters and an inner shutter with wooden louvers to which is fixed a stainless steel mosquito mesh. A mild steel grill is fixed into the frame between the two layers. At night, the upper part is closed and the inner layer of the lower part opened which allows good ventilation. This is particularly appropriate for the bedrooms.
This is a consistently elegant design and a great resolution of many design issues involving wind towers and solar panels. One quibble could be that Doshi appears to be overcommitted to modernist aesthetics. Could an unplastered house not save significant amount of cement? However, building in Pune, Doshi’s options for unplastered construction are limited. Brick quality is bad in Maharashtra in general and stone is now prohibitively expensive. However, mud remains an option. If Doshi does explore that, it would be interesting to see what kind of aesthetic he would develop out of the constructional constraints and possibilities of that material.