Team Canada's solar roof

The biennial Solar Decathlon kicked off yesterday in Washington D.C., a competition between 19 universities to make net-zero energy homes. The houses will be judged on multiple factors related to comfort, energy production, and affordability. A team from Germany won in 2009 and 2007.

This is Team Canada's house made by students from the University of Calgary. The building's shape draws inspiration from native American tipis. But the rounded roof made of solar panels has an additional benefit: by positioning panels this way, they operate at 93 percent of optimal efficiency. Like other houses, this one uses a reflective white roof on the other side which lightens the cooling load.