At the 2011 Solar Decathlon, where collegiate teams are displaying their super-efficient model homes for judging in Washington, D.C., Planet Forward host Frank Sesno speaks with Don Ferrier, president of Ferrier Custom Homes, about green roofs.

(Related Photos: Solar’s Model Homes at the 2011 Decathlon)

Using the University of Maryland WaterShed model home as a starting point, Ferrier discusses the costs and benefits of green roofs, and some of the implementations he’s been part of. Green roofs can be pricy — a large installation might run $20,000 — but see why Ferrier thinks the benefits of this cooling system can outweigh the costs.

But the real question is: Solar panels or a green roof? The Solar Decathlon’s Empowerhouse, designed by a team of students from four different schools, uses both. Planet Forward’s expert Bill Worthen of the American Institute of Architects comments via our Ask an Expert feature: