Climate change-related heat stress is believed to be one of the greatest threats to human health. Poor people in particular are at high risk of heat-related illnesses. Heat stress, already a problem in the warm, low-lying Indo-Gangetic plain, is likely to further intensify in the coming decades. Several innovative and traditional building measures have been tested to some extent, but mostly on an individual basis and with solutions targeting the upper and middle classes. What temperature levels people are actually exposed to, both inside and outside of their houses, and whether low-income housing can offer sufficient protection against heat are still open questions.

The issue

Temperatures are rising as a consequence of climate change. The heat wave events of 2015 in Pakistan and India showed the catastrophic consequences of extreme temperature on humans, even in regions where one would expect people to be accustomed to heat. The heat wave resulted in the loss of more than 4,000 lives. But the problem is not confined to areas historically considered hot. Extremely high temperatures have been observed in mountainous areas, and the need for cooling and cooling devices during the summer season is increasing all over the HKH. In urban areas, the heat is exacerbated by the urban fabric, concrete and built-up mass, limited ventilation or vegetation, and many anthropogenic sources of heat make cities several degrees warmer than the countryside. Options to escape the heat are limited.

The implications of this microenvironment can be substantial. Active-cooling air conditioners can achieve the necessary indoor-temperature reductions, but they are less accessible to the poor, energy-intensive, and therefore counterproductive to global mitigation efforts – especially in the global south, where primary energy demand is skewed toward cheaper non-renewable energy sources. However, certain strategies already exist that help reduce indoor temperatures, like improved building design, using appropriate insulation and both reflective and isolation materials. At a larger level, strategies are based on improving environmental conditions: street corridors can be designed as ventilation paths; vegetation cools through shade and evapotranspiration; open water brings relief, if refreshed; and water bodies may be used as heat/cold storage facilities. These strategies help achieve temperature reductions or improve thermal comfort. However, the poor remain vulnerable, because they cannot afford active cooling mechanisms and have limited opportunities to install passive cooling mechanisms to cope with the extreme heat.

Most measures that have been tested seem to take the temperature down by one to three degrees, so an integration of approaches is required, including not only combinations of technical solutions, but collaborations with city designers, architects, project developers, and most importantly, local stakeholders. A better understanding of varying heat exposure related to the environment will help design low-cost interventions in resource-poor countries.

The solution

ModRoofs, developed by ReMaterials  and promoted by Mahila Housing Sewa Trust (MHT) in Delhi, are especially designed to replace asbestos/corrugated tin roofs in a low-income setting and are a way of insulating the roof with co-benefits. ModRoof is a modular roofing system for slum and village homes in the developing world.

The main component of the roofing system is blue panels that are custom manufactured from packaging and agriculture waste. To address the challenges of operating in the developing world, ReMaterials designed the roofing system to be modular, allowing easy shipment, installation, and replacement of individual panels.

The ModRoofs, which are made from recycled materials and are water-resistant, were especially developed for slum houses and the marginalized, which make it an interesting and realistic measure to test. Together with MHT, TERI, Wageningen Environmental Research, and partners will do a thorough continuous analysis of indoor-temperature reduction to see whether during the daytime a 5-6 °C air temperature reduction can be achieved. If so, this would provide further support for outscaling this innovative solution.

The accompanying graph depicts the indoor diurnal temperature range across 45 low-income houses in Delhi on 15-16 April 2016. It shows a large variation in both night and daytime temperatures, indicating that there is room for improvement using existing techniques.

Contributors

Tanya Singh, WER, tanya.singh@wur.nl Ganesh Gorti, TERI, ganesh.gorti@teri.res.in Christian Siderius , WER, christian.siderius@wur.nl Suruchi Bhadwal, TERI, suruchib@teri.res.in

Further reading/information

Eijrond, V. (2016, February 12): Heat Stress and Effective Heat Adaptation Measures.