Roofs that reflect sunlight save electricity
Delhi is set to become more energy efficient. Chief Minister Sheila Dikshit has asked the Bureau of Energy Efficiency and municipal bodies to build cool roofs in new buildings, especially the government ones. She gave the directions in mid-September. Such roofs reflect sunlight and heat unlike the conventional dark ones that absorb heat (see ‘How cool roof mechanism works’).
“Cool roof at ITC Green Centre in Gurgaon reduces surface temperature by 30°C and saves energy of air conditioning in the top floor by 10 to 15 per cent,” says Niranjan Khatri, general manager, environment unit at the company. According to a study by Lawrence Berkeley National Laboratory (LBNL) in the US and International Institute of Information Technology in Hyderabad (IIIT-H), commercial buildings can annually save 13 to 14 kWh/m2 of energy by switching to cool roof. A commercial building with 150m2 roof area can save up to Rs 15,000 annually in the electricity bill.