As India’s urban centres continue to expand in population and infrastructure, they are becoming hotspots for escalating climate change impacts. By 2030, over 40 percent of India’s population is projected to be living in urban regions, according to the latest Economic Survey 2023-24.

Among various rising urban challenges, heat stress is one of the pressing issues leading to increased energy consumption, health risks and additional strain on infrastructure. A major contributor to heat stress is the Urban Heat Island (UHI) effect, which results in urban areas experiencing markedly higher temperatures due to dense construction, impermeable surfaces, lack of green spaces and anthropogenic heat. Anthropogenic heat means heat generated by buildings, vehicles, machinery, or people.

Every year, several cities in states such as Delhi, Haryana, Uttar Pradesh, Madhya Pradesh and Gujarat report record-breaking summer temperatures, making urban heat a public health issue requiring resilient infrastructure. The UHI effect primarily and disproportionately affects low-income and vulnerable communities, highlighting the need for inclusive and scalable solutions.

In response, cool roof materials such as paints, membranes and tiles have emerged as a scientifically verified, economical solution that mitigates urban heat while enhancing energy efficiency and human well-being.

What cool roofs do

Designed to reflect more sunlight and absorb less heat than conventional roofs, cool roofs offer a scientifically sound and accessible strategy to tackle rising urban temperatures. This is primarily done by applying solar-reflective materials or coatings that possess a high solar reflectance index. This means they reflect a larger portion of solar radiation while maintaining significantly cooler surface temperatures as compared to conventional roofs.

Conventional construction materials for roofs such as reinforced cement concrete, asbestos cement sheets, galvanised iron sheets/metal roofs and ceramic or clay tiles (uncoated) have a low reflectance value, ranging from 20-30 percent.

These materials absorb a significant amount—about 40-75 percent—of solar radiation through the day due to their high thermal mass. As the temperature decreases in the evening, the retained heat is released slowly, leading to elevated nighttime temperatures. This results in discomfort and health risks for city dwellers, particularly those living in informal housing or poorly ventilated structures. It also increases the demand for artificial cooling, creating additional strain on energy systems. Appropriate roofing materials can mitigate the demand for Heating, Ventilation and Air Conditioning (HVAC) systems.

Research has indicated a reduction in cooling energy demand by 21–26 percent with the implementation of cool roofs, leading to significant energy savings and lower carbon emissions from electricity generation. The building envelope acts as an interface between the interior and exterior environments. The solar energy absorbed and reflected by it contributes to the HVAC load within the building.

Among its various components, the roof is a crucial element that accounts for approximately 50–60 percent of the total cooling load. Cool roof applications saw a significant decrease in interior and exterior surface temperatures of about 4.1 degrees Celsius and 9.2 degrees Celsius, respectively. Indoor room temperature was lowered by approximately 2-5 degrees Celsius, reducing the need for cooling appliances.

Sustainable and affordable

Cool roofs are particularly beneficial because of their affordability and adaptability. A simple coat of solar-reflective white paint or cool roof coating can alter a standard rooftop into a heat-reflective surface in existing buildings. Implementing cool roof materials from the initial stages of construction in new buildings can ensure long-term thermal comfort and energy efficiency.

Due to their low installation and maintenance costs, cool roofs stand out as a practical, affordable, adaptable and sustainable solution. They provide thermal comfort to the building occupants amidst rising heat without the requirement for major infrastructural changes. Simultaneously, they reduce the UHI effect, positively reducing heat stress among vulnerable and marginalised communities.

In India, aligning with the government’s Indian Cooling Action Plan, and the Heat Action Plans developed by state governments, several Indian cities including Delhi, Ahmedabad, Hyderabad and Jodhpur have initiated their cool roof implementation programmes, as part of energy-efficient and sustainable cooling solutions to combat climate change.

The Municipal Administration and Urban Development Department of the government of Telangana introduced India’s first Cool Roof Policy 2023-2028, making Telangana the pioneering state to undertake this initiative at the state level.

With a vision to transform Telangana into a heat-resilient state, the policy seeks to promote widespread adoption of cool roofs by mandating the installation of cool roofing materials such as solar reflective paints, tiles, or sheets, across all government, residential, and commercial buildings, as well as housing schemes.

Climate-responsive ratings

GRIHA (Green Rating for Integrated Habitat Assessment), jointly established by The Energy and Resources Institute and the Ministry of New and Renewable Energy, government of India, has been acknowledged as India’s own green building rating system.

As a climate-responsive rating framework, GRIHA rating variants advocate for the integration of passive design strategies and cool roof implementation for enhancing thermal comfort by lowering indoor temperature, optimising energy consumption by reducing cooling loads, and mitigating the UHI effect through material efficiency.

Aligning with global and national sustainability goals, the inclusion of these strategies contributes to the broader vision of reducing the environmental footprint of built spaces and enhancing urban heat resilience. To facilitate the adoption of cool roofs and mitigate urban heat, GRIHA Council has collaborated with various organisations and entities.

Towards inclusive urbanscapes

India’s climate discourse is recognising urban heat as a significant issue. Addressing the challenge of increasing urban heat, sustainable solutions such as cool roofs can build resilience, especially for those on the frontlines of urban heat stress.

However, to effectively tackle the UHI effect and heat stress in the built environment, a holistic, integrative and multi-pronged approach is essential.

The initial design stage of a building is the most effective and critical phase of construction. At this point, a combination of complementary strategies can be implemented to ensure the optimisation of both indoor and outdoor environments for better thermal comfort, energy savings and improved liveability. These include incorporating vegetative covers, vertical gardens and roof gardens, as well as integrating passive design principles such as optimal building orientation and cross-ventilation.

Integrating these strategies with cool roof implementation can significantly improve surface temperature and air quality, enhance energy efficiency and promote long-term resilience against the impacts of climate change. For transformational change, unlocking its full potential necessitates multi-stakeholder collaboration, sustained policy support, public engagement and integration into mainstream urban planning and building codes.

-360info