The walls of buildings facing east or west are usually built with hollow bricks. Explnin Why.

Explanation

The thermal conductivity of the insulating brick is 0.15`Wm^(-1)K^(-1)` and that of concrete is 0.8 `Wm^(-1)K^(-1)` and that of air is `0.024Wm^(-1)K^(-1)`. Since air is a bad conductor of heat, heat from the Sun falling on the wall is poorly conducted into the rooms.
This renders the living rooms and bed rooms cooler than ones not using the hollow bricks.