MITs "chameleon" tiles promise to slash building energy use

Anyone with even a passing knowledge of physics knows that dark surfaces absorb heat, while white surfaces are more effective at reflecting heat – hence the growing number of experts arguing that people should paint buildings white to help tackle global warming.

But now a team of MIT graduates reckon they may have worked out a way for buildings to enjoy white surfaces in the summer, before switching to darker surfaces in the winter when buildings typically need to maximise the sun's heat, and there isn’t a paint brush in sight.

According to the university, a team of recent graduates have developed a new tile that changes colour as the temperature changes, producing a white surface when hot and a black surface when it is cold.

Dubbed the Thermeleon, to rhyme with chameleon, the researchers claim that in their white state the tiles reflect about 80 per cent of sunlight landing on them, while in their dark state they reflect around 30 per cent of the sun's energy.

The team, which last week won a $5,000 prize as part of MIT's annual Making and Designing Materials Engineering Contest (MADMEC), is now looking at developing a commercial version of the technology that will be able to cope with harsh outdoor weather conditions.

The current version of the technology uses a common commercial polymer in a water solution, which is then trapped between plastic layers, one of which is coloured black. When the temperature drops below a level determined by the nature of the solution the white polymer dissolves revealing the black surface.

MIT said the team is now working on an even simpler and lower cost version of the technology that will effectively integrate the polymer solution into a paint that could then be painted straight onto existing black roofs.