Quote TCEToday:

ROOF tiles which can change colour depending on the temperature could offer large energy savings for households.

The tile has been developed by a team of graduates from the Massachusetts Institute for Technology (MIT), who call themselves Thermeleon. The tile turns white in hot weather to reflect heat, and black when the temperature drops to absorb heat, saving energy on both air conditioning and heating.

White roofs have been hailed by many as a way to reduce the energy expense and therefore greenhouse gas emissions associated with air conditioning. However, in cooler or more temperate climates, white roofs would mean precious heat being lost, where a black roof would absorb heat, potentially reducing the need for heating. A colour-changing roof tile could solve both of these problems.

The Thermeleon tile consists of a black background and a common polymer dissolved in water and encapsulated by flexible plastic layers. Below a certain temperature, the polymer stays dissolved in the water and the black background shows through. When the temperature rises, the polymer condenses out of solution and forms a film of droplets which scatters light and blocks out the black background, thereby creating a white surface. The temperature at which the polymer comes out of solution can be changed by varying the precise formulation. In laboratory tests, when white, the tile reflects around 80% of light falling on it. Thermeleon predicts that the tiles could save up to 20% of cooling costs.

The team now hopes to develop the idea further by micro-encapsulating the polymer solution and incorporating it into a clear formulation which could be painted onto existing black roof tiles, saving money as roofs would not have to be replaced. They will also test and improve the durability of the system.