How to let the wind in, and out
Among the major hurdles for air movement is the larger indoor spaces we are creating in our buildings.
Let us try this quiz – ask a hundred people if they appreciate traditional homes, and possibly the majority would say ‘yes’. Now ask if these houses get fresh air inside, and possibly the majority would say ‘no’.
Traditional homes would have few windows in the external walls and often a central court, together ensuring air circulation. Most owners cancelled courtyards, the poor built smaller houses and in some regions courts were anyway uncommon – so the stale air stayed in.
The best means of ensuring air circulation continues to be having an opening to the sky – a skylight if covered with glass, with or without a sunken courtyard. Enclosed rooms like bedrooms that cannot get a skylight, can have tall windows going up to roof level with vent at top.
In earlier times, most houses were rectangular in plan, with rooms distributed all around in geometrical shapes. Thus, one external wall of one room would get only one window. Now, let us try staggering them – push one room inside and pull one room outside. Thus, the external wall of the house would not be a rectangle with the wall line going in and out. We realise there can be many more windows in all orientations, many more corners for the room and generally much better air circulation inside.
Wind does not move in all orientations equally. Every region has its dominant directions, e.g. Kerala gets largely south-west wind, while Chennai has it from south-east. These larger trends further change directions due to trees, buildings, ground levels, seasons and such others, causing microclimatic modifications. As such, every site will have certain windward directions where pressure is high and leeward directions, where pressure is low. Wind blows from the higher to the lower pressure areas, hence windows can be located in such directions to get better indoor air movement.
Among the major hurdles for air movement is the larger indoor spaces we are creating thanks to technology. Smaller the room width, better the air circulation, but we are building large spaces necessitating ceiling fans. Even worse condition can be experienced in closely built crowded areas. The compactness nullifies all possible green cover and wind around the building, finally demanding an air conditioner. As such, both the house planning and city planning play major roles in indoor air.
Scientifically drawn-up data called wind rose diagrams are freely available today, though they may not be accurate for every site in a compact layout, but the general ideas can improve the situation largely. Roof-top fans called turbo ventilators are today popular, which need no electricity.
Past societies learnt how to live with wind, with sailors in the sea and farmers on land being the best examples. It was an animal instinct displayed by all, be it birds when they migrate or humans when they build vernacular structures. Somewhere down our modernising process, we seem to have lost this knowledge. It’s time to regain it.