For thermal comfort
Knowing daylight and shadow patterns round the year is helpful, and common sense observation can be the starting point for understanding light and shade balance in buildings.
Often we see design ideas going through a paradigm shift, nearly to the opposite ends. To realise this phenomena, look at this — from the past practice of building for shade inside the house and outside on the walls, today we are seeing buildings washed with light everywhere. Accordingly, windows on the walls have become larger, external walls are exposed to direct sunlight and skylights have been introduced.
While the theory of light is desirable, the resultant heat built-up is a nuisance no one can live with, hence the need for ideas to shade the building. From an eco-friendly perspective, the more shaded the building, the more cool would be the inside space. In case of air-conditioned structures, this would reduce energy needs; and if not, we achieve more effective passive cooling.
Emergence of chajjas
During the early years of modern architecture in India, simple projected chajjas were introduced. Most people think they are mainly for rain, which is not true. As shading devices, though without specific considerations of direction, depth of projection and materiality, they continue to be popular in India.
Thinking architects like Le Corbusier experimented with alternative forms, and came out with specially inclined concrete walls outside the window, often called as Brise Soleil. Much before him, the Golconda building at Pondicherry had a series of horizontal concrete fins. Such external skins placed closely to the walls allow wind movement and let in diffused light from the bright tropical sun but prevent direct solar radiation into indoor spaces.
Indian traditional designs did not use an external skin, but provided deep overhangs like at Fatehpur Sikri or built external walls as perforated jaalis to reduce heat built-up as found in Jaisalmer. Or positioned wooden louver-based features as walls as seen in the Padmanabhapuram Palace. Of course these are among the best examples we get, with thousands of variations with lesser effect commonly found all over our country.
While all the above measures are valid and much needed, our data base for ensuring shade has drastically improved over the years. For every region now there are solar charts – specifically locating the sun in technical terms like altitude and azimuth for any given minute of the year.
It is possible today to calculate the exact pattern of shade for any given time using manual formulae or computer simulated software driven programmes. These measures assist in designing the shading device to derive increased shade in summer and increased sunlight penetration in winter. India being in the southern hemisphere with high summer sun and low winter sun is a difficult place to design for, considering our vast geographical extent and regional diversities.
No single solution can serve year-round needs; hence we need to think judiciously to derive maximum benefits across the seasons. While computer software can help, common sense observation and following the right kind of precedence can be the starting point towards a building where light and shade are balanced.