By Paul Kurtz, KYW Newsradio 1060

PHILADELPHIA (CBS) -- A gathering of movers and shakers in the "green roof" and "green wall" industry is taking place this week at the Pennsylvania Convention Center.

This year's theme is "Restoring Urban Waters."

Clayton Rugh, of Xero Flor America in North Carolina, was showing off photos of some of the green roof projects his company has manufactured since it opened ten years ago.

"A lot of people like them because of the aesthetic quality -- or in other words, a flowering roof," he says.  "It's also a great way to capitalize your investment on your roof since it lasts two or three times longer than it normally would."

Green roofs and walls are also helpful in dealing with storm water runoff, says Stephen Peck, a spokesman for  Green Roofs for Healthy Cities, the industry association that organized the conference.

"When you have a city that has so much impervious area," Peck says, "large volumes of water run off into the receiving water bodies -- the Schuylkill and the Delaware rivers. It threatens beaches, and we have problems with the quality of the water we drink."

Industry experts and vendors will be sharing their ideas through Saturday.