Scientists at MIT have invented a smart roofing material that takes a new thermal-management approach to eco-design. It's a different approach to previous efforts, of which there are many. We've rounded them up for you, starting with the latest, below.
MIT's Black and White Solution
MIT's Thermeleon material is a composite of layers that makes it thermochromic--on exposure to heat it changes color from black to white. It works by sandwiching a common polymer between flexible plastic layers, with a black one at the back--when cold the polymer solution stays dissolved and the black rear face shows through, and when it heats up the solution condenses to form light-scattering droplets.
The upshot is that when the sun is shining a roof tile covered in the material is white-colored, scattering up to 80% of the sunlight back and thus keeping the building beneath the roof cooler. The result is a 20% reduction in cost to keep the interior at a comfortable temperature in the summer, a figure which also comes with an eco-friendly drop in the electricity supply demands. During winter, of course, you'd prefer your roof to capture as much heat as possible from the sun, which is where the black coloring is handy--the tiles scatter just 30% of incoming solar radiation then.
The team's working on micro-encapsulating the chemicals, so that in future they may work as a paintable or spray-on coating, and then if the prices drop to match the innovation, the tech could also find much use in the developing world.
Penn State Uni's Cylindrical Solar Tiles
If you're wanting to generate electricity directly from photovoltaic cells on your roof, Penn State University has an interesting suggestion--which we wrote about back in September.
This solution involves using curved instead of flat Roof tiles--these actually capture more sunlight during the day. Until now they've only been found in specialist commercial applications. The team matched the Solyndra curved panels with a lower green-colored roof to boost their efficiency and offset the heating effect of a darkened roof panel by having many plants underneath.
LMN Architect's Living Roof
Speaking of the cooling effect of plants, check out the design of the Vancouver Convention Centre from LMN Architects, which we wrote about a few months ago:
The 400,000 plants integrated into the structure help regulate the temperature inside, and along with the other eco-friendly systems built into the design the result is a drop of 60% to 70% in water consumption, compared to other similarly-sized convention centers.
SRS Energy's Disguised Solar Tiles
Both of the solutions above result in a roof that looks significantly different to the traditional tiled solution--a situation that means in some places they'll come into conflict with local planning laws designed to keep buildings looking similar. That's where SRS Energy's Solé Solar Tiles come in--they're actually a marriage between a traditional clay tile, and a photovoltaic cell.
The cell is formed as a flexible thin-film unit, and bonded to a dark colored clay tile, so that they look like any other tile. The resulting product is modular for extra-easy installation, cheaper and lighter than a traditional silicon solar cell solution.
Dow Chemicals' Covert Solar Tiles
If your house design calls for a shingled roof instead of a tiled one, and you live in an area where theft of expensive roof-top solar panels is a problem, then Dow Chemicals has a neat trick.
Its Solar Shingles use thin-film copper indium gallium diselenide technology to make them cheap and light, and they're designed to be intermingled with traditional asphalt roof tiles on a roof. That makes for easy installation, and lower visibility to street-level thieves.
And there you have it: Proof positive that in the future, our building roofing will do much more for us than keeping the sun, wind, and rain off our heads. They all make good sense, of course, since traditional roofs spend all their time staring at the sun rather than harnessing its rays for energy. Now if there were only a clever hybrid of all these different ideas....