Passive cooling solutions to counter oppressive heat conditions

The impact of heat in India has been severe in recent years, with numerous heat-related deaths, widespread reports of heatstroke and school closures reported. This year, the thermometer climbed above 40°C in many places in late April, earlier than normal, according to a United Nations Environment Programme (UNEP) feature.

“Even if nations start bringing down the greenhouse gas emissions warming the planet, temperature extremes are here to stay for the foreseeable future,” said Balakrishna Pisupati, who leads the United Nations Environment Programme’s (UNEP) India office. “Facing the kind of oppressive heat we have seen, people across this country will need to adapt, especially in ways that do not worsen the climate crisis...This is where passive cooling solutions come in, he adds.

According to the UNEP feature, passive cooling solutions range from reflective roofs to cool pavements to shade-providing tree cover. Crucially, and unlike air conditioning, these solutions do not spew out planet-warming greenhouse gas emissions nor enflame the climate crisis. India has emerged as a global champion of passive cooling, integrating these approaches into national policies and city planning, often with the support of UNEP.

As UNEP states, India’s cities are particularly at risk due to climate change and extreme heat, as rising temperatures are exacerbated by urban heat island effects and inequitable access to cooling. Left unchecked, this heat could expose up to 200 million people in India to lethal heatwaves in the 2030s, reduce India’s GDP by 2%, cause the loss of 34 million jobs, and make it that much harder for millions of people to escape poverty. India’s cities cannot just air-condition a way out of this extreme heat crisis. Best practices from India and around the world show that by taking a whole-systems approach to urban cooling, Indian cities can solve their cooling challenge and increase their heat resilience. Urban cooling and cold chain are two critically under-supported areas under the India Cooling Action Plan (ICAP). Two projects, delivered under the framework of the UNEP Cool Coalition, will support the Government of India to lead a transition to sustainable, accessible and climate-friendly cooling.

One such project is in the Indian capital. Delhi is one of the hottest major cities, with temperatures reportedly feeling like 50°C with humidity. To help give commuters relief from the heat, the UNEP-led Cool Coalition in partnership with national and local government bodies are installing a “cool roof” on the bustling Kashmere Gate interstate bus terminal. The roof, which covers nearly 150,000 square feet, will be retrofitted with a surface that reflects at least 80% of solar heat, helping to cool upwards of 100,000 commuters daily.

Another example is the Pradhan Mantri Awas Yojana–Urban (PMAY) – India’s flagship affordable housing scheme; to date, it has provided safe, secure homes to millions of families. However, in many affordable housing projects across India, keeping cool remains a challenge. Together with UNEP, PMAY aims to integrate passive cooling features – such as natural ventilation and insulated walls – into the 10 million homes the government targets for delivery by 2029. These efforts could reduce electricity use by up to 35%, by lowering indoor temperature by 3°C and giving families 40% more time in the year without needing cooling.

Again, in the city of Chennai in southern India, where dense population, high-rise buildings and shortage of green space are causing temperatures to spike, attempts are on to reduce this so-called heat-island effect. UNEP’s Cool Coalition and India’s CEPT University mapped the city’s hottest areas and provided officials with recommendations on how to use nature and passive cooling to bring down temperatures. These are being integrated into Chennai’s masterplan and can reduce urban heat by up to 4°C and cut heat-caused illnesses by 15-30%.

Furthermore, according to the feature, in India, most cities do not take a standardized, scientific approach for mapping urban heat, which is essential to developing plans that address scorching temperatures. To change this, UNEP and partners are supporting central and state government efforts in India to adopt cutting-edge strategies for identifying and addressing urban heat hotspots and helping develop guidelines on how these government agencies can use disaster-related funding on projects to reduce temperatures in urban areas.