Energy efficient. Keeping urban heat islands cool in summer

The rise in temperature not only adversely affects agriculture but also makes summers increasingly unbearable. Studies from around the world have shown that urban areas are more vulnerable as concrete structures and concrete-topped lanes and by-lanes absorb heat, adding at least 2-4 degrees to the temperature.

Cities like New York, Los Angeles and Toronto have experimented with strategies to mitigate the adverse impact of ‘urban heat islands.’ An urban heat island, or UHI, is a place which is a lot warmer than the rural areas surrounding it.

The policy push

Taking a cue from global experiments, Telangana, the third most urbanised State in the country, has introduced a cool roof policy. The 36-page policy mandates all structures beyond 600 square yards to follow prescribed norms.

Cool roofs, the policy asserts, can reduce inside temperatures by 2.1-4.3 degrees Celsius. As an offshoot, it will also reduce power consumption as the load and demand on air-conditioning comes down proportionately. The policy’s target is to achieve a cool-roofed area of 7.5 sq km, including 5 sq. km in Hyderabad, in the first year (2023-24) of the five-year policy.

By the end of the initiative, the State aims to cool-roof 300 sq km in the State, including 200 sq km in the Hyderabad agglomerate, which includes urban areas abutting it. Besides reducing the heat, the policy is looking at saving 600 million units of power through reduced demand for air-conditioning by 2028-29.

How to chill

So, what is a cool roof? It is a surface which can reflect sunlight back to the atmosphere and can emit any absorbed heat. This helps reduce temperature inside a building and cuts the power required for air conditioning the interiors. Several products are available for cool roofing, including cool metal roofing, coatings, membranes, tiles, terra-cotta tiles and white tiles. “The cost of ceramic tiles for cool-roofing is around ₹30-40 per sq ft. The scope for variance in products is less as white is what is good for reflecting sunlight,” an executive of Gujarat-based Essence Tiles said.

An array of reflective paints is also available both, online and offline. Reflective painting coats are available in different-sized packs, with prices starting from ₹300/kg. While tiles and coating materials are widely used, there are some other products like roofing shingles that are available in the ₹55-105 range per sq ft. Some prefer to use traditional terracotta tiles which starts as low as ₹5.

In the policy’s first phase, the State government will make it mandatory for government buildings, hospitals, shops, non-residential complexes, educational institutions and housing for the poor to deploy cool roofs. C Shekar Reddy, Chairman of CII (Telangana) and Chairman of CSR Estates, said the move will help sustainability efforts. “Cool roofing is not new to our tradition. Houses in villages do have several cool-roofing techniques. This is the minimum we should do in urban areas to reduce temperatures in buildings and houses,” he said.

Reddy, who is also the chairman of the Indian Green Building Council (IGBC-Hyderabad Chapter), said urban areas have become heat islands as every bit of land is covered. IGBC is championing green ways of construction across India and would like the Telangana government to be more pro-active in the project.

The challenges

Vishal Garg, who is director at Indorama Ventures Center for Clean Energy, Palaksha University (Punjab), and has done seminal work in urban heat islands and energy efficient building models, also welcomed the move. He said, “The cool roof policy is a timely and necessary step towards creating sustainable, energy-efficient and climate-resilient cities, ultimately enhancing the well-being of millions of Indians.”

However, he said there were concerns about the quality of products that could swarm the market during the policy’s implementation. “I think the biggest challenge is to ensure good quality products are deployed. Poor products have a short life and lose their ability to reflect rather too quickly,” Garg said if it fails, people will lose trust in the initiative. But as a first step, this one was in the right direction.

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