Five Sustainable Solutions to Tackle Extreme Heat in South Asia

As climate change exacerbates heat stress globally, sustainable cooling solutions are urgently needed. This year, South Asia set several deadly heat records: New Delhi recorded its highest July temperature in 90 years at 43.6°C, and Karachi saw its highest April temperature in 74 years at 44°C.

A report by the Climate Action Tracker indicates that even if the latest pledges from COP26 are fulfilled, global temperatures could rise by over 2.4°C this century. Research shows that even a 2°C rise could expose a billion people to extreme heat stress. Despite efforts to control greenhouse gas emissions, the world could reach the 1.5°C threshold, the aspirational target of the Paris Agreement, within years. Sustainable, low-carbon, and accessible cooling technologies and practices are essential, especially for the poorest and most vulnerable populations.

1. Empowering Women Through Low-Cost Cooling Solutions

Poor neighborhoods often consist of cement houses with plastic covers or tin sheets that absorb and retain heat, creating hot and uncomfortable living conditions. The Mahila Housing Trust (MHT), an Indian NGO, works in 10 cities across India to enhance community resilience to heat stress, focusing on women who are particularly vulnerable as their work often takes place within the home. MHT provides advice on affordable, easily implementable passive cooling methods.

  • Solar-reflective paint: Painting roofs and sun-facing walls can reduce indoor temperatures by 4-5°C. Light-colored roofs reflect 80% of sunlight’s energy, compared to 5% for dark roofs.
  • Vegetation: Growing potted plants and creepers on roofs can reduce indoor temperatures by 2.5°C through shading and evapotranspiration.
  • Renovating roofs: Using recycled materials and adding vents to roofs can reduce temperatures by 6-7°C. MHT has helped about 200 houses in Bhopal and Ranchi implement these changes.
  • Building orientation: Proper orientation during construction can reduce heat stress, saving on electricity for cooling.

Since 2014, MHT has helped over 2,000 families adopt heat-resilient measures, earning the 2021 Ashden Award for Cooling in Informal Settlements.

2. Geothermal Air-Conditioning

GeoAirCon, a Pakistani company, uses the stable temperatures below the Earth’s surface to cool homes.

  • Geothermal heat pumps: A loop of underground pipes filled with fluid is installed, and geothermal heat pumps move heat around the system. During summer, these pipes draw heated water from the building and move it underground, cooling the building to a comfortable 21-25°C.
  • Efficiency: GeoAirCon systems are twice as efficient as conventional air-conditioning. They cost USD 260-460 to install and are cheaper to run. Although more suited to houses with outdoor spaces, the technology can be installed in densely populated areas with minimal space.

GeoAirCon systems have been installed in 12 buildings in Pakistan and were runners-up for the 2021 Ashden Award for Cooling in Informal Settlements.

3. Low-Impact Cooling Systems

India’s CBalance consultancy promotes passive cooling design and ventilation to reduce reliance on traditional air conditioning. Their Fairconditioning program fosters cooperation between architects and urban communities to minimize artificial cooling needs and promotes energy-efficient technologies.

  • Evaporative cooling: Uses evaporated water to cool air without refrigeration, requiring much less energy. In Pune, this system reduces conventional AC use by 40%.
  • Radiant cooling: Circulates cool water through buildings, used in 73 large buildings in India.
  • Solar power: Uses solar energy to chill water.
  • Energy-efficient AC units: Promotes AC units that emit fewer greenhouse gases.

4. Cool Roofs Programs

The Ahmedabad Heat Action Plan (HAP) in India, in partnership with the Indian Institute of Public Health and the Natural Resource Defense Council, painted over 7,000 low-income households’ roofs white, potentially saving 1,100 lives annually. The Million Cool Roofs Challenge is a USD 2 million initiative to scale up solar-reflective roofs in developing countries. In Bangladesh, the roofs of factories and buildings were painted, reducing indoor air temperatures by over 7°C.

5. Vernacular Architecture

Traditional materials, techniques, and designs have provided sustainable cooling for centuries.

  • Mud and bamboo houses: In Rudrapur, Bangladesh, houses built using these materials, with openings for cross-ventilation and coconut fiber insulation, keep interiors cool.
  • Traditional stilt houses: In Assam, these houses enable cross-ventilation and shading, with unplastered walls promoting natural ventilation.

Policy and Urban Planning for Sustainable Cooling

As global emissions drive temperatures higher, these methods and technologies must be rolled out more widely. Finance is the main obstacle to wider adoption, according to both MHT and GeoAirCon. Urban planners and policymakers need to incorporate sustainable cooling into development plans. For example, the Hanoi City Master Plan 2030 in Vietnam aims to prevent heat build-up using ventilation corridors of green and blue spaces, aligning with the country’s net-zero by 2050 commitment.

As South Asia warms and urbanizes, similar heat adaptation and mitigation measures must be integral to city development plans.

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