"Green roof" building is exploding in Washington. In 2006, D.C. had 301,751 square feet of green roofs; by 2009 it was approaching 2 million square feet. And now that the Environmental Protection Agency is proposing increased water runoff regulations, more developers might be embracing environmentally friendly roofs. Cole, vice president of Maryland's Cole Roofing, explains. Why are green roofs better for the environment?

Of course they help manage storm water runoff. But they also dissipate the urban island effect. Urban environments have a whole lot of black rooftops, so especially during the summer, temperatures in the city might be 10 degrees or more than out in the suburbs. So adding a green roof dissipates that heat... They can decrease sound pollution by providing that buffer that plants do. And they help reduce heating and cooling costs [by] increasing insulation.

Are green roofs expensive?

Relative to a typical roof, they can be a fairly significant additional cost. But the idea is ... is there enough to offset the additional cost? Large [footprint] developers like Home Depot or Lowe's ... they're required to build a storm water runoff pond. By putting in a green roof, they can limit storm water runoff thus allowing them to develop smaller land. That can open up additional property locations for them.

What could stricter regulations mean for developers?

It's forcing developers to think about the long-term operational energy efficiency for the project and maybe moving away from 'get it built as fast as you can for the lowest cost.' ... If that's understood and talked about at length, a tenant can understand why they benefit from being in that kind of building. As an industry we're confident that putting a vegetated system over the top of a roof ... [which] protects the roof and makes it last longer.

Liz Farmer