With each passing year, hundreds of millions of Indians eye the approach of summer with trepidation. This year, the thermometer climbed above 40°C in many places in late April, earlier than normal. 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.
Commenting on the present situation, Balakrishna Pisupati, who leads the United Nations Environment Programme’s (UNEP) India office, said, “Even if nations start bringing down the greenhouse gas emissions warming the planet, temperature extremes are here to stay for the foreseeable future. Facing the kind of oppressive heat we have seen, people across this country will need to adapt, especially in ways that don’t worsen the climate crisis.” Thus, the role of the passive cooling solutions is coming into the picture.
Passive cooling solutions range from reflective roofs to cool pavements to shade-providing tree cover. Crucially, and unlike air conditioning, these solutions don’t 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. A few examples are below:
Cooling Delhi’s rooftops
The Indian capital of Delhi is one of the hottest major cities on the planet, with temperatures reportedly feeling like 50°C with humidity earlier this month. 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.
The project, supported by the Swiss Agency for Development and Cooperation, is part of a larger effort by the government and the UNEP-led Cool Coalition to blunt the effects of heat waves on Delhi and protect the city’s most-vulnerable residents.
Lowering the temperature in social housing
Pradhan Mantri Awas Yojana–Urban (PMAY) is 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.
UNEP is helping PMAY 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.
That’s part of a broader UNEP effort to reduce the heat in low-income neighborhoods. UNEP is also partnering with several agencies in the state of Tamil Nadu to develop financing mechanisms that would support the integration of passive cooling into government-supplied social housing.
Heat-proofing Chennai
Located in southern India, Chennai is a major industrial hub prone to punishing heat waves that typically sweep through ahead of the annual monsoon. Home to over 12 million people, Chennai’s dense population, high-rise buildings and shortage of green space are causing temperatures to spike. 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 recommendations are being integrated into Chennai’s master plan and can reduce urban heat by up to 4°C and cut heat-caused illnesses by 15-30%. The effort has been supported by the Swiss Agency for Development and Cooperation, the Government of Denmark, the Clean Cooling Collaborative Initiative, and the World Bank.
