Mr. X was advised by an architect to make outer walls of his house with hollow bricks. The correct reason is that such walls

Hollow bricks are primarily used in construction for their superior thermal insulation properties. The air trapped within the cavities of these bricks acts as a poor conductor of heat [1]. This thermal barrier significantly reduces heat transfer through the walls, ensuring that the interior of the building remains cooler during the summer and warmer during the winter [1]. Unlike solid bricks, which are dense and readily transmit heat, hollow bricks help maintain stable indoor temperatures and improve energy efficiency by reducing the load on air conditioners and heaters. While they offer benefits like being lightweight and providing better soundproofing, they are generally less suitable for load-bearing structures compared to solid bricks and do not inherently protect against lightning or moisture seepage better than treated solid alternatives.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > FASCINATING FACTS > p. 92