Roof tiles to cool the planet

Colour-changing roof tile works with the weather 

A roof tile that turns white in the heat of the sun, reflecting its rays back into space, is the latest techno-fix solution for cooling the planet [see ‘Paint it white’, GF73].

Developed by students at the Massachusetts Institute of Technology, the ‘thermeleon’ slate incorporates a polymer – similar in structure to hair gel – mixed with water and sandwiched between two layers of plastic. When the weather is cold the slate remains black, but when the sun shines, the polymer/water mix reacts and the slate turns white, reflecting heat and light back out to space.

The MIT team is also working on a paint version of the invention that can be sprayed onto existing slate roofs to create the same effect.

White roofs can cut indoor temperatures by up to 20°C, reducing the need for energy-intensive cooling systems. It’s a smart solution with high-profile advocates. In 2009, Al Gore joined New York Mayor Michael Bloomberg in a campaign to paint 100,000 square feet of rooftops – part of a plan to cut the city’s emissions by 30%. – Lorna Howarth

2 February 2010

Lorna Howarth