With This Self-Cooling Roof, You Might Not Need AC A new, ultra-reflective roof material is the firs

As summers keep getting hotter because of climate change, it sets up a vicious cycle: By the end of the century, the world may be using more than 30 times more energy for air conditioning, pushing temperatures up even more. But a new variation on cool roofs could help.

A typical dark roof soaks in sunlight, heating up the building underneath and releasing more heat back into the surrounding neighborhood at night. While cool roofs–made from white, reflective material–aren’t new, they still absorb some heat. A new material is the first to actually stay cooler than ambient air.

“What we set out to do was maximize the solar reflectance to see how far it could be pushed…to see the extent of further improvements that are possible with open roofing technologies,” says Angus Gentle, a researcher at the University of Technology Sydney, who developed the material along with physics professor Geoff Smith.

By adding layers of plastic on top of silver, the researchers were able to create a roof surface that bounces sunlight back into space, leaving it as much nine degrees cooler than a state-of-the-art cool roof. “The coating keeps the roof cool by reflecting almost all of the incoming solar radiation,” Gentle says. “A vast majority of this emitted radiation goes directly into space without being absorbed by the atmosphere.”