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.

The Guardian

US newsmag’s green rankings

A leading U S weekly newsmagazine, has ranked CB Richard Ellis (CBRE) No 45 in its 2009 green rankings.

The list measures the environmental performance of the 500 largest US-based publicly traded companies.

The ranking is based on each company’s actual resource use and emission levels, its environmental policies and strategies, and its reputation among its peers. CB Richard Ellis is the highest ranked commercial real estate company. “In India and around the globe, we are showing in our own operations and our work with clients that sustainable practices are good for both the environment and the bottom line,” said CB Richard Ellis’ Anshuman, Magazine, Chairman & Managing Director, India.  The newsmagazine collaborated with three research partners to compile the rankings, KLD Research & Analytics, Trucost, and CorporateRegister.com, and also referenced data provided by the Carbon Disclosure Project, which collects GHG data on over 2,500 companies worldwide. CBRE has participated in the Carbon Disclosure Project since 2007.

In 2007, CB Richard Ellis became the first commercial real estate services company to announce a commitment to become carbon neutral in its own operations. In addition, CB Richard Ellis is assisting property owners and occupiers with energy efficiency programs at building space it manages around the world. The complete rankings, and methodology, are available at http://greenrankings.newsweek.com.