There were times when a small opening would be provided below the roof of rooms to take out the foul air, but most builders have discontinued that practice.
The statement that a big central window is necessary for better air movement is a big myth. A room with one side window, however big it is, gets least air since there is no provocation for air to enter or exit. When we plan for air with opposite openings, there would be more windows than walls in the room.
While air gets in, heat gets trapped as well. Slowly we realise, our house however well planned, is climatically uncomfortable. Then starts the usual appreciation about how cool the grandma's house is!
So, what do we do? Typically, Bangaloreans would argue how the city has grown with tree cutting and more vehicles; hence resign to the fate of living in a heated house.
Most rooms have 10' feet clear height with lintels at 7', leaving the top one-third area without any openings. There were times when a small opening would be provided here to take out the foul air, but most builders have discontinued that practice. Also, the air just below the topmost roof gets warmer with no escape, in turn creating a zone of stagnant air.
Air lock zone
The easiest way to prove this air lock zone is to put on the fan – for quite some time the breeze we get is warmer and foul. It takes part of an hour depending on the room volume to ensure complete air change.
So, what do we do? We live in the so-called garden city of India, but crib about the rooms getting stuffy, with inadequate fresh air.
Designing for a cool house is among the simplest of common sense ideas our past generations followed, during the days of no electricity. It also ensured understanding air. The major challenge is to take out the foul air, the air we breathe out, the air affected by our body temperature and the air heated at the roof zone.
A few openings just under the roof achieve this purpose, termed as displacement ventilation. Modern aesthetics do not appreciate these pigeon hole-like voids! For nearly 15 years now in our firm, we have merged this vent with the window, taking the window opening up to the roof bottom. It has worked well.
The second major need is for body-level air movement. Air moves from windward directions, where air pressure is high, to leeward areas where pressure is low. However, in a city with compactly placed houses, predicting these air currents is difficult. Hence, we can simply provide multiple but small openings distributed across the external walls. To this end, every room should have at least two sides as external walls. In smaller plots, often, it is not easy to achieve this.
Slightly staggering the setbacks with varying widths, where the house wall projects or recedes, helps in ensuring more external wall positions. We can then have windows to more directions — to north, south, east or west.
(The writer is an architect, working for eco-friendly designs, and can be contacted at firstname.lastname@example.org)
Keywords: eco-friendly architecture