Context: Telangana has become the first state to notify a Cool Roof Policy to effectively address the issue of heat waves and urban heat island. IPCC reports have highlighted that incumbent climate change will intensify heat & humidity in India. Under the policy, Telangana plans to achieve around 300 sq. km of cool roof area by 2028.
- A Cool roof takes in less heat from sun than regular roofs. It stays relatively cool in the sun by reflecting (minimize solar absorption) and emitting thermal radiation (to help dissipate solar heat gain).
- Cool roofs reflect around 80% of sunlight while regular roofs reflect only about 20%, keeping buildings significantly cooler.
Cool Roof techniques
- Cool roof techniques can be broadly divided into three categories:
- Coated Cool Roofs: These roofs involve the coating of a material or paint with high reflectivity on top of a conventional roof material to increase the roof surface’s Solar Reflective Index (SRI). These are liquid applied coatings made of simple materials white in colour. Ex. Lime wash, Acrylic polymer, Plastic technology.
- Membrane Cool Roofs: These roofs involve using pre-fabricated materials like membranes or sheeting to cover an existing roof to increase the roof surface’s solar reflectance and thermal emittance. Ex. Polyvinyl chloride, bitumen based.
- Tiled Cool Roofs: These roofs involve the application of high albedo, ceramic mosaic tiles or shingles on top of an existing roof or to a new roof.
- Green roofs and rooftop solar systems: Policy also supports application of Green Roofs and Rooftop Solar Systems. Green Roofs make use of vegetation to help the roof absorb less solar energy by providing a thermal mass layer to reduce flow of heat into a building. Vegetation is especially helpful in reflecting infrared radiation.
- Minimum Requirements Cool Roof Materials: For qualifying as a cool roof, roofs with slopes less than 20o shall have an initial solar reflectance of no less than 0.70 and initial emittance no less than 0.75.
Application of Policy
Mandatory cool roofing: Government, Non-residential & Commercial Buildings, Residential buildings with plot area more than 600 sq yards and Government assisted housing constructions.
Optional cool roofing: All other buildings
Benefits of Cool Roofs
- Increased thermal comfort: Cool roofs can help keep indoor temperatures 2.1-4.3oC lower than households with traditional roofs.
- Climate freindly cooling solution: Cool roofs are estimated to reduce air conditioning costs by 20% of the building leading to saving of cost and electricity and lower greenhouse gas emissions.
- Limited maintenance and costs: Cool roofs need minimal maintenance and a cool protective coating can be reapplied periodically. Often initial material costs for cool roofs are comparable with traditional roofing materials and can also be applied on existing buildings.
- Longevity of roof: Application of cool roof increases the longevity of roof beneath it, by acting as a protective layer.
- Address Urban Heat Island Effect: City-wide installations of highly reflective roofs and pavements along with planting shade trees, has potential to reduce city’s ambient air temperature by 2oC in summer month. Thus, reducing urban heat island effect.
- Equitable solution to heat stress for poor and low-income households: Heats stress hits the poor the hardest due to lack of access to cooling and their houses are often made of heat-trapping materials such as tin sheets, asbestos, plastic or tarpaulin without sufficient ventilation leading to health hazards and reduced productivity. Cool roofs are especially relevant to provide thermal comfort to poor & low-income households.
Other Initiatives for Cool Roofs
Million Cool Roofs Challenge: It is an initiative launched by Sustainable Energy for All (SEforAll) and NESTA Challenges in 2019 which awarded $125,000 in grants to 10 finalist teams based in South Africa, Bangladesh, Ivory Coast, Philippines, Indonesia, Kenya, Mexico, Niger, Rwanda & Senegal. In less than two years, collectevily the 10 countries managed to apply more than 1.1 million sq. m. of cool roofs.
Cool Roof Challenge: National Disaster Management Authority (NDMA) had launched inviting cities to announce targets and implement cool roofs in 2021.
Heat Wave Vulnerability In India
- A heatwave is an extended period of hot weather relative to expected conditions of the area at that time of year.
- Heat wave has emerged as one of the deadliest natural hazards often causing more deaths than all other natural hazards.
- Heat waves have a slow onset and are silent killers unlike other disasters.
- Greenhouse has emissions led Climate change has increased Earth’s temperatures by close to 1.10oC. Each year earth’s temperature cross previous limits.
- Meteorological events like La Nina and El Nino also cause localised warming and cooling of planet. In the Indian context, El-Nino particularly increases chances of heat waves in the Indian subcontinent.
- Urban Heat Island effect: This is a phenomena under which urban and suburban areas experience elevated temperatures compared to their outlying rural surroundings. The annual mean air temperature of a city with one million or more people can be 1 to 3°C warmer than its surroundings, and on a clear, calm night, this temperature difference can be as much as 12°C. Heat Island effect leads to increased heat risk in cities. Reasons for Heat Island effect are: Air Pollution which traps heat, concretisation & blackening of surfaces which traps heat.
- Large and informal workforce of India makes India particularly vulnerable to heat waves who often work in less ventilated buildings or in the outdoors.
IMD Criteria for Heatwaves: IMD declares a heatwave when:
- Temperature of a place crosses 40oC in the plains, 37oC in coastal areas and 30oC in the hills.
- Temperature of a place is 4.5-6.4oC more than the normal temperature for the region on that day.
- Temperature of a place crosses 4.5oC.
Way forward for Heat Wave
- All States to formulate & implement Heat Action Plans in line with NDMA’s guidelines on Heat Wave.
- Need to strengthen existing Early Warning Systems.
- Need for understanding the local thresholds of Heat Wave.
- Data on Heat: Automatic Weather Stations networks needs to be expanded in cities and states.
- Vulnerability analysis: A comprehensive, country-wide assessment of heat vulnerability and hyper-local heat action plans is required.
- Heat waves should be notified as disasters at the national level under existing disaster relief policies. Currently, several states have declared heat waves as a local disaster. Ex. Odisha, Maharashtra etc.
- Land use change: Promoting Urban forests/farms, community gardens, rejuvenation of wetlands and shading of areas with trees.
- Building materials: Promoting Green roofs and other materials that increase albedo, LEED compliant green building architecture, Home insulation. These solutions should be made part of building codes and effectively enforced.
- Heat related work standards should be notified by Ministry of Labour and public health institutes to make workers work easily in high heat situations.
- Provisions for Emergency: First Aid Kits, Drills for Heat Waves, Heat Wards in Hospitals etc.
- Long Term solutions: Green Transition, Limiting Emissions and controlling climate change.