Grey+south is cool formula: South-facing homes with grey glass windows best plan

Hyderabad: Keeping in mind the soaring levels of mercury nationwide, researchers from the National  Institute of Technology-Suratkal (Mangaluru) have worked out a formula that can significantly reduce heat from building up inside homes.

The NIT researchers found that a south-facing house made of laterite bricks, with windowpanes having grey glass and a 1.5-metre window overhang  is more  temperature-moderated and energy efficient than any other combination.

The researchers hit upon the formula after studying summer climactic conditions in Hyderabad, Ahmedabad, Kolkata and Bengaluru and analysing over 300 models of buildings, using  various construction materials.

According to the research findings, the absorptance of grey glass is 49 per cent, compared to just 16 per cent of transparent glass. Absorptance indicates the percentage of  radiation that a glass absorbs.

The higher the absorptance, the better. Saboor Shaik, who was on the team, said, “Grey glass is also beneficial for the environment as its reflectance, the amount of radiation it reflects back into the environment, is low, just five per cent compared to eight per cent of transparent glass. Grey glass outperforms green glass, bronze glass and blue green glass in absorptance and reflectance.”

Scientists recorded a radiation of 33 Kilo Watt Hour (KWh) from a grey glass window located on the south-facing wall with a 1.5-metre window overhang. The figure was 40.95 KWh for a window without the overhang, located on an east-facing wall and having transparent glass.

Ventilators also play an important role in maintaining energy efficiency in a house.
S. Srinivas, deputy executive director, CII-Sohrabji Godrej Green Business Centre, said, “Fresh air supply of 10-12 cubic feet per metre is required in a building so that the air does not become stale. Each room should have windows that make up least eight per cent of the carpet area.”

But is a south-facing house okay as per Vastu norms? City-based vastu expert
A. Hanumanth Rao says, “A house can face in any  direction but its construction and architecture should be as per the laws of Vastu.

It is a myth that a house should be facing only the east or the north-east. Many homes in Chennai constructed as per Vastu norms are south facing. Vastu is a science and, therefore, practical, not rigid as many believe.”