Amid rising heatwaves, ‘Cool-Roofs’ can save lives. Here’s how

Several states in north India are in the grip of an intense heatwave. Extreme heat has allegedly killed many people. As per news reports, in the past couple of days, around 100 people have died due to heatwaves in Bihar and Uttar Pradesh (UP), with Ballia district of UP reporting highest casualty.

Extreme temperature events have profound — even fatal — impacts on human health. Rapid rise in heat gain due to exposure to hotter than average conditions compromise the body's ability to regulate temperature and can result in a surge of illnesses.

During a heatwave, there is a significant increase in stress, anxiety, and depression that may trigger or exacerbate mental, behavioural, and cognitive disorders.

There are simple and cost-effective methods to reduce the impact of the heat and save lives. ‘Cool roofs’ is one such intervention to beat the sweltering heat of summer.

Simply put, cool roofs reflect sunlight and absorb less heat. Depending on the setting, cool roofs can help keep indoor temperatures lower by 2 to 5°C (3.6 - 9°F) as compared to traditional roofs.

According to National Disaster Management Authority’s (NDMA) ‘Heatwave Action: House Owners’ Guide to Alternate Roof Cooling Solutions’, published in April 2021, “Roof contributes up to 70% of the heat gain of a building during high temperatures. Solar radiation striking a surface is either reflected, absorbed, or transmitted. Cool Roofs through use of reflective materials and techniques, help in reducing heat absorption and improving overall thermal comfort of the building.”

Cooling Roof Solutions

As per the NDMA document, there are various cooling solutions for existing homes. These include Bamboo/Thatch Screening, Green Net Shading, Roof Paint, Gravel Roof, Heat Insulation Tiles, Hollow Concrete Tiles, Broken China Mosaic, Mud Phuska, etc.

Bamboo, Thatch & Palm leaves are locally available across India and can be installed as a secondary roof screen thereby reducing the heating effect.

Roof mist cooling system reduces the roof surface temperature by spraying an extremely small amount of water across the roof. Spraying allows the roof to cool as the water evaporating from the surface captures the heat.

Cool roof coatings are applied to steep as well as low sloped roofs in good condition. Coatings can be applied to both new roofs and existing roofs.

Hollow concrete/terracotta tiles have high thermal insulation and sound insulation property which is very effective in limiting heat flow. The air inside the cavities provides the insulation to heat.

Using earthen pots to keep roofs cool has been traditionally practised in hot and dry areas. Locally available earthen clay pots are affordable and exhibit high thermal insulation property.

LoChina mosaic terrace provides a reflective layer to the roof which reflects a considerable amount of solar radiation falling on the roof. The reflective layer is formed by broken and randomly sized pieces of light coloured ceramic tiles, laid on a cement mortar bed, with joints between tiles sealed with white cement.

Telangana’s Cool Roof Policy

Telangana is the first state in the country to launch a ‘cool-roof’ policy. The policy, launched on April 1 this year, will be applicable for a period of five years (2023-2028). The cool roof policy is aimed at making the state thermally comfortable, heat resilient and to also cut down energy consumption, setting an example for other states in the country.

The Cool Roof policy in Telangana is now mandatory for all government, government-owned, non-residential and commercial buildings irrespective of the site area or built up area. Occupancy certificates will be issued only after ensuring compliance with the policy.

For residential buildings that have a plot area of 600 square yards and above, cool roof application is mandatory. For buildings that have a plot area of less than 600 square yards, it is optional or voluntary.

Also Read: 54 dead, 400 hospitalised amidst extreme heat in UP’s Ballia. Where are the heat action plans?

According to Telangana’s policy, there are three different types of material which could be used for cooling the roofs. In the first type, roofs can be coated with a material or paint having high reflectivity. These are liquid applied coatings made of simple materials such as lime wash, or an acrylic polymer or white plastic coating.

In the second type, prefabricated materials such as poly-vinyl chloride (PVC) membranes or bitumen-based sheeting can be used to cover an existing roof in order to increase the roof surface’s solar reflectance and thermal emittance.

Also Read: Bihar: IMD Declares ‘Red Alert’ in 6 districts; 48 Dead Due To Heat Wave – Here’s How To Protect Yourself

The third type of cool roofs involve the application of high albedo, ceramic mosaic tiles or shingles on top of an existing roof or to a new roof, the policy document said, further adding that the choice of an appropriate cool roof material depends on some range of factors, such as the existing roof material, durability and maintenance and availability of skilled labour.

Also Read: Getting Hammered from Pole to Pole and Tropic to Tropic

Meanwhile, leading cities in India are developing and demonstrating cool roof programs for local conditions. For example, Ahmedabad has a cool roofs programme for over 3,000 low income homes as part of its heat action plan.

Hyderabad has a demonstration pilot aimed to design a broader program as part of its building energy efficiency program. The national government is working toward sustainable cooling with the National Cooling Action Plan and energy efficiency programs for buildings, air conditioners and fans.

Also Read: Feeling The Heat

The Benefits Of Cool Roofs

Cool roofs save energy and costs by reducing cooling load requirements in a building. By keeping the temperatures inside the top floor of a building lower, cool roofs reduce the need for air conditioning, providing more affordable cooling. They also reduce the energy loads in buildings that do have air conditioning.

Cool roofs help reduce the urban heat island effect, improve air quality and combat climate change. By keeping city temperatures lower, cool roofs also help in reducing air conditioning energy consumption in buildings.

Cool roofs enhance durability and appearance of roofs. By keeping roof structures from heating up through applying cool roofing techniques, cool roofs can prevent excessive expansion and contraction of the materials and reduce cracking incidences, prolonging the roof’s life.

Cool roofs increase energy access by reducing peak load on the grid. By reducing cooling needs in air-conditioned buildings, cool roofs can reduce peak load on the grid during the heat season, enabling lesser load shedding during the peak summer months.

Cool roofs help build community resilience to extreme heat, increasing community resilience to cope with heat waves can lead to fewer heat-related illnesses and casualties.