A simple and cost-effective solution to beat the heat, 'cool roof' was recently introduced in Telangana for a five-year period from 2023 to 2028, making it the first state to do so.
But much before Telangana, as part of a heat action plan, it was introduced in Ahmedabad. The technique – and the heat action plan – found so much success that it "serves as a standard template for many cities and states across India and internationally," Dr Abhiyant Tiwari, Lead - Health & Climate Resilience, Natural Resources Defense Council (NRDC), told The Quint.
So, what exactly is a cool roof? How does it help lower temperatures? What led to Ahmedabad's heat action plan? We have all the answers.
'Cool Roofs' in Telangana & Ahmedabad: How Does This Heat-Proofing Method Work?
1. What Is a Cool Roof & How Does It Work?
A cool roof is a design that involves coating the roof of a building with solar reflective paint covered in white tiles or with a white membrane.
And how will doing so help lower temperatures? Well, it all boils down to physics.
Darker-coloured roofs made using standard materials tend to absorb more heat than lighter-coloured standard roofs, as the colour black absorbs all wavelengths of light and reflects none, while the colour white reflects all wavelengths of light, and therefore, absorbs the least amount of heat.
This was actually proven by a study by the Lawrence Berkeley National Laboratory in the United States. The lab tested black, white, and green roof types to determine the Solar Reflectance Index or SRI (which is essentially an indicator of the ability of a roof surface to return solar energy to the atmosphere).
Roofing material surfaces with a higher SRI will be cooler than surfaces with a lower SRI under the same solar energy exposure.
The study found that a roof with a clean, smooth, and bright white surface was found to have an SRI of 107, the surface of a standard grey roof had an SRI of just 19, and a roof with a clean, smooth 'cool colour' surface, such as a cool red tile, had an SRI of 38.
So, apart from its heat-reflecting qualities, why are cool roofs beneficial? Dr Abhiyant Tiwari explained to The Quint, "It is a cheaper alternative to things like air conditioners, which are energy-consuming."
Expand2. Why Has Telangana Opted for Cool Roofing?
In its cool roof policy, the Telangana government highlighted how the state that is located on the Deccan plateau is vulnerable to heatwaves.
Additionally, the government added that the state is "on a high growth trajectory with rapid urbanisation increasing the demand for cooling."
Telangana is the third-most urbanised state in India, with 47 percent of its population living in urban areas – and the numbers are likely to exceed 50 percent soon. "The policy is aimed at reducing heat island impact and heat stress in the state," said Rama Rao.
Heat islands contribute to higher daytime temperatures, reduced nighttime cooling, and higher air pollution levels, while heat stress occurs when the human body's way of controlling its internal temperature starts to fail.
Expand3. How Did Ahmedabad Become a Success Model?
In May 2010, Ahmedabad was in the throes of a deadly heatwave where temperatures surpassed 48 degrees Celsius and claimed the lives of 800 people.
It was so deadly that bats and birds dropped dead from the trees they roosted in. A slow-moving cyclone made things worst.
After the devastating heatwave, the Ahmedabad Municipal Corporation partnered with the India Institute of Public Health-Gandhinagar (IIPH-G) and the US Natural Resources Defense Council (NRDC) to develop India's first heat action plan (HAP).
Moreover, like many other cities in the global south, Ahmedabad's temperature is expected to go up. The average summer temperature in the 2030s or the next decade may rise about 2 degrees Celsius, according to a forecast by state government-funded research.
Expand4. What Are the Key Aspects of Ahmedabad's HAP?
A research by Dr Jeremy Hess, director at the Center for Health and the Global Environment, University of Washington, has credited the Ahmedabad HAP with averting about 1,190 deaths each year since it was implemented.
The heat action plan, according to Dr Dileep Mavlankar, the director of IIPH-G, has four primary components:
SnapshotFirst is the early warning, which includes issuing a threshold-based alert. "For instance, when the temperature is above 45 degrees Celsius, we issue a red alert, when it is above 43 degrees Celsius, we issue an orange alert, and when it is above 41 degrees Celsius, we issue a yellow alert," he explained.
Second is public awareness, including media awareness through several meetings about how to protect oneself from heat and what the consequences of exposure are.
Third is preparing medical and paramedical staff to deal with heat emergencies.
Fourth is taking short-term measures like creating a water distribution system and long-term measures like running a citywide cool roof programme.
In 2020, the city announced a cool roof programme for more than 15,000 slum roofs and 1,000 government buildings as part of its heat action plan. The focus of the larger rollout was on slum households and local government buildings.
The Mahila Housing Trust has installed over 100 cool roofs in low-income communities in Ahmedabad using solar reflective paint and a technology called ModRoof – a locally made material using coconut husk and paper waste. And it seems to have worked.
(At The Quint, we are answerable only to our audience. Play an active role in shaping our journalism by becoming a member. Because the truth is worth it.)
Expand
What Is a Cool Roof & How Does It Work?
A cool roof is a design that involves coating the roof of a building with solar reflective paint covered in white tiles or with a white membrane.
And how will doing so help lower temperatures? Well, it all boils down to physics.
Darker-coloured roofs made using standard materials tend to absorb more heat than lighter-coloured standard roofs, as the colour black absorbs all wavelengths of light and reflects none, while the colour white reflects all wavelengths of light, and therefore, absorbs the least amount of heat.
This was actually proven by a study by the Lawrence Berkeley National Laboratory in the United States. The lab tested black, white, and green roof types to determine the Solar Reflectance Index or SRI (which is essentially an indicator of the ability of a roof surface to return solar energy to the atmosphere).
Roofing material surfaces with a higher SRI will be cooler than surfaces with a lower SRI under the same solar energy exposure.
The study found that a roof with a clean, smooth, and bright white surface was found to have an SRI of 107, the surface of a standard grey roof had an SRI of just 19, and a roof with a clean, smooth 'cool colour' surface, such as a cool red tile, had an SRI of 38.
So, apart from its heat-reflecting qualities, why are cool roofs beneficial? Dr Abhiyant Tiwari explained to The Quint, "It is a cheaper alternative to things like air conditioners, which are energy-consuming."
Why Has Telangana Opted for Cool Roofing?
In its cool roof policy, the Telangana government highlighted how the state that is located on the Deccan plateau is vulnerable to heatwaves.
Additionally, the government added that the state is "on a high growth trajectory with rapid urbanisation increasing the demand for cooling."
Telangana is the third-most urbanised state in India, with 47 percent of its population living in urban areas – and the numbers are likely to exceed 50 percent soon. "The policy is aimed at reducing heat island impact and heat stress in the state," said Rama Rao.
Heat islands contribute to higher daytime temperatures, reduced nighttime cooling, and higher air pollution levels, while heat stress occurs when the human body's way of controlling its internal temperature starts to fail.
How Did Ahmedabad Become a Success Model?
In May 2010, Ahmedabad was in the throes of a deadly heatwave where temperatures surpassed 48 degrees Celsius and claimed the lives of 800 people.
It was so deadly that bats and birds dropped dead from the trees they roosted in. A slow-moving cyclone made things worst.
After the devastating heatwave, the Ahmedabad Municipal Corporation partnered with the India Institute of Public Health-Gandhinagar (IIPH-G) and the US Natural Resources Defense Council (NRDC) to develop India's first heat action plan (HAP).
Moreover, like many other cities in the global south, Ahmedabad's temperature is expected to go up. The average summer temperature in the 2030s or the next decade may rise about 2 degrees Celsius, according to a forecast by state government-funded research.
What Are the Key Aspects of Ahmedabad's HAP?
A research by Dr Jeremy Hess, director at the Center for Health and the Global Environment, University of Washington, has credited the Ahmedabad HAP with averting about 1,190 deaths each year since it was implemented.
The heat action plan, according to Dr Dileep Mavlankar, the director of IIPH-G, has four primary components:
First is the early warning, which includes issuing a threshold-based alert. "For instance, when the temperature is above 45 degrees Celsius, we issue a red alert, when it is above 43 degrees Celsius, we issue an orange alert, and when it is above 41 degrees Celsius, we issue a yellow alert," he explained.
Second is public awareness, including media awareness through several meetings about how to protect oneself from heat and what the consequences of exposure are.
Third is preparing medical and paramedical staff to deal with heat emergencies.
Fourth is taking short-term measures like creating a water distribution system and long-term measures like running a citywide cool roof programme.
In 2020, the city announced a cool roof programme for more than 15,000 slum roofs and 1,000 government buildings as part of its heat action plan. The focus of the larger rollout was on slum households and local government buildings.
The Mahila Housing Trust has installed over 100 cool roofs in low-income communities in Ahmedabad using solar reflective paint and a technology called ModRoof – a locally made material using coconut husk and paper waste. And it seems to have worked.
(At The Quint, we are answerable only to our audience. Play an active role in shaping our journalism by becoming a member. Because the truth is worth it.)