In Ahmedabad, India, where the temperature soared to 108 degrees on Monday—and where high temperatures will stay well over 100 for at least the next 10 days—it’s even hotter inside small shacks in slums, where thin metal roofs trap heat. A local startup designed an alternative: modular roofing panels made from paper and wood waste that can help keep homes cooler.
“When I started the company, I traveled across four states of India, rural areas, urban slums, and spoke to 600 families,” says Hasit Ganatra, the founder and CEO of ReMaterials, the startup that makes the Modroof. “And I kept seeing these roofs which needed change.” Most were made from either thin corrugated metal sheets or thin cement. “We would go to villages and slums and see people spending time outside of their house on summer afternoons, and they’d say, ‘This house is like an oven. We can’t stay inside.'” Heat strokes are common; more than 6,000 people have died in India from heat waves over the last decade.
As climate change is making the country hotter, India has one of the fastest-growing markets for air conditioners. (Unfortunately, the increase in air-conditioning is also adding to global warming, though new technology is emerging.) But millions of people can’t afford air conditioners. Changing the design of a small house can help only to some extent. One McKinsey report predicted that by the end of the decade, parts of India will be at risk of heat waves that are so extreme that humans may not be able survive outside, even in the shade. But on a more ordinary hot day, if a change in a building can lower the temperature, it can make a large difference for the people living inside.
The Modroof design uses cardboard waste and natural binders to make a lightweight panel that’s insulated and has a coating that renders it waterproof. A metal structure makes it strong. The insulation, along with an air gap inside the panel, helps keep heat out. In tests, the company has shown that the new roof can make a home as much as 18 degrees Fahrenheit cooler than it was previously.
The roof is also designed to keep homes dry in monsoons; metal roofs often corrode and develop holes that leak, and concrete roofs develop cracks. Ganatra visited one family after a heavy rainstorm and saw that they were carrying all of their belongings outside to dry off. “I asked them about it and they said, ‘Yeah, we had to crawl up in one corner of the house because it was raining and we’ve stayed up all night.’ And this was a routine for them.”
The roofs are more expensive than cheap metal sheeting, but cost less than concrete slabs because they’re easier to install. The startup partnered with microfinance companies to offer loans. (Some families are separately painting their metal roofs white, a cheaper option that can also help lower the temperature.) Over the last few years, the company has installed 500 roofs. While the pandemic has slowed its growth, Gantra hopes his company can expand to countries in Africa and South America. “It’s very easy to ship, it’s very easy to install, it’s very easy to repair or maintain,” he says. “And we can do everything over a WhatsApp video call—we can get these installed anywhere in the world. We have not gone outside India, but it’s only a matter of time before we do.”