Within the growing urban vulnerability, it is the poor and those who live in informal settlements that will be the hardest hit. There are close to 14 million slum households across India (Census 2011). Measures to lower impact on these families will be essential, particularly from the growing heat stress.
A first look at what makes slum houses vulnerable reveals the typical tin house for what it is—a hot metal box clad in combustible materials where temperatures could easily reach 51⁰C. The story of heatwave vulnerability, however, is not about the tin house but about the people who live in them.
The residents of Masudpur slum of Vasant Kunj in Delhi, for example, said that summer was the most difficult time of the year. Yet, mainstream market options to improve thermal comfort were either too expensive or too alien to ever be adopted in settlements like this one. It needed simple do-it-yourself options.
Was it possible to use the community’s own strengths as the basis for effective retrofits to improve thermal comfort? Over a few months at the end of 2018, SEEDS helped prototype and test such retrofits, analysing their performance both in real time and through EnergyPlus simulations. Multiple community feedback events ensured they were acceptable to the slum community; and a manual was published with step-by-step instructions on creating and installing them.
The final prototypes were five-fold. A double roof made from billboard flex awnings reduce the heat gain from the roof (the major source). A skylight and vent was made with a simple hole, steel wire mesh and plastic bucket, helping cool and light the house. The army of drums used to store water were stacked vertically in a stand made with bamboo ladders. This also supported a desert cooler and potted plants, redirecting and filtering rainwater from the double roof for collection.
A retractable flexible ceiling made of billboard flex and bamboo helped the house cool down and heat up as required. Finally, cycle tyre tubes (usually used as lining on the door to prevent scrapes) were used to line the top of the tin walls, breaking the thermal bridge with the tin roof.
These five small micro-innovations could truly help beat the heat. For together, they cost just INR 2,500 to make and could reduce internal temperature by over 10⁰C (as validated by Visvesvaraya National Institute of Technology, Nagpur).