Ask anyone who lives in a west-facing flat in Delhi, Ahmedabad or Hyderabad: the afternoons are hot. There is a clear physical reason, and there are practical solutions.
Why the west is hottest
By the afternoon, the air temperature is at its peak and the building has been absorbing heat all day. At the same time, the sun is low in the western sky, so its rays strike west walls and windows almost head-on, entering deep into the room. East windows receive similar low sun, but in the cooler morning.
Why overhangs aren't enough
A horizontal chajja works brilliantly on a south façade, where the sun is high. On the west, the sun is too low; it simply shines in beneath the overhang.
What works
- External shading is far more effective than internal curtains, because it stops heat before it passes through the glass. Options include vertical fins, external blinds, jaali screens and bamboo chiks.
- Deep balconies and verandas create a shaded buffer.
- Trees and creepers on the west side provide shade and cool the air by evaporation.
- Solar-control glass or film reduces heat gain while letting light through.
- Light-coloured exterior walls and roofs reflect more of the sun's energy.
- Night ventilation: open windows after sunset to flush the stored heat out.
The Vastu view
Traditional Vastu advises fewer and smaller openings on the west and heavier walls on the south-west. Seen through building science, that guidance helps reduce afternoon heat gain — a good example of tradition and climate sense pointing in the same direction.