You learn something new everyday, if you allow yourself. Here’s what I learned, thanks to Dara Colwell of Alternet:

Green Roofs: Building for the Future

From the U.S. Food and Drug Administration building in Washington DC to Heinz Corporate head quarters in Pittsburg, an increasing number of buildings are swapping shingles for sedums. The movement is called green roofing, but far from an industrial paint job, it evolves around technology that’s ecologically-sound — and proving so useful that cities like Portland, Oregon, Chicago, Boston, Seattle, and the entire state of Maryland are eagerly exploiting the potential of this once forgotten façade.

“This technology offers us an opportunity to significantly improve not only the way our buildings operate, but to utilize wasted spaces — there are millions of square miles,” says Steven Peck, founder and president of Green Roofs for Healthy Cities, an organization established to increase awareness of green roof benefits. GRHC also hopes to advance the market in North America. “The roofing industry is just at the beginning of a process of transformation. Nothing can match the range of social, economic and environmental benefits green roofs provide.”

As the name implies, green roofs are roofs made of plants. They’re comprised of a waterproof membrane followed by a root barrier, a drainage layer, and finally the growing medium and a variety of plants, grasses, sedums, cactus or shrubs — hence, the green. The technology, of course, isn’t entirely new. For millennia, the natives of Scandinavia and Iceland, particularly barren environments with limited building materials, used sod on their roofs as insulation; in Tanzania, mud huts with grass roofs are common; and closer to home, many early settlers used sod to insulate their walls and prairie grass to cover their roofs. [full text]