The ‘Cool Roof’ initiative implemented in Chennai’s Perumbakkam has drawn international attention, with the United Nations Environment Programme (UNEP) citing it as a replicable climate innovation for rapidly urbanising regions. Recognised as a scalable urban heat mitigation model, the project is now being considered for similar rollouts in India’s capital, Delhi, and other heat-prone cities.
This intervention, developed in partnership between the Tamil Nadu government, the UNEP-led Cool Coalition, and the Rocky Mountain Institute, is part of a larger urban heat resilience framework. A pilot was launched at the Lighthouse Project in Perumbakkam, where cool roof technology using high solar reflective paint was applied to two residential blocks. The result was a tangible temperature drop of 5 to 8 degrees Celsius within homes during peak summer months—transforming thermal comfort in affordable housing sectors.
According to officials from Tamil Nadu’s Environment and Climate Change Department, the material used—Silka Cool Roof Paint—has a Solar Reflective Index (SRI) of 102, making it highly efficient in reflecting solar radiation and reducing heat absorption. This passive cooling strategy offers a low-cost, high-impact solution for vulnerable urban populations grappling with extreme temperatures.
The significance of the Chennai model lies not just in its design but in its context. The city’s combination of dense high-rise clusters, limited tree cover, and growing concrete footprint makes it particularly susceptible to the urban heat island effect. The UNEP report highlights that Chennai’s ongoing urban planning reforms—such as incorporating passive cooling into the city’s master plan—could reduce citywide ambient temperatures by up to 4°C and heat-related illnesses by up to 30%.
The initiative is part of a broader national movement, where India is increasingly being recognised as a global leader in passive cooling strategies. UNEP notes that such interventions are being mainstreamed into national policies like the Pradhan Mantri Awas Yojana–Urban (PMAY-U), where energy-efficient design elements such as ventilated layouts and insulated walls are being added to affordable housing for 10 million families by 2029.
Inspired by Chennai’s success, similar passive cooling retrofits are underway in Delhi, including the installation of a 150,000-square-foot cool roof at the Kashmere Gate interstate bus terminal. This structure is expected to benefit up to 100,000 daily commuters, particularly during the sweltering summer months. By reflecting 80 per cent of solar radiation, the design substantially reduces heat buildup, offering real-time comfort in densely used public spaces.
UNEP is also collaborating with state-level institutions in Tamil Nadu to explore innovative financing models to support wider adoption of these technologies in public housing. The focus is not just on heat reduction but also on achieving equity in climate adaptation—ensuring that low-income communities, often at the frontline of climate vulnerability, are not left behind in the shift toward resilient infrastructure.
While the cool roof initiative may appear simple in design, its implications are far-reaching. It represents a pragmatic blend of policy, innovation, and equity—offering cities a roadmap to adapt effectively to a warming climate. As global temperatures continue to rise, India’s urban centres are proving that affordable, scalable, and sustainable cooling solutions are not only feasible but necessary.
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