I fell in love with the idea of green roofs before I fully understood the concept. The thought of decreasing rainwater run-off by attaching plants to a roof just blew my mind. And as I’ve learned how rooftop plants lower energy costs and help cool buildings in the summer, I’ve been itching to tour the green roof at the PECO building in Philadelphia.
I got my chance last week when I joined the PA Horticultural Society’s Young Friends group on a tour of the roof (followed by yummy drinks across the street at Bistro St. Tropez). The night was hot and humid as I walked from 30th St station to the PECO building. But once I got up on the roof there was a beautiful breeze. Without all of that dark rooftop tar, the sun’s heat is less intense than on typical urban roofs. The only things absorbing sun up there are sedums (a genus of drought and heat tolerant plants) and meadow grasses. They serve as insulation for the building, which employees say is warmer in the winter and cooler in the summer now that the roof has been installed.
Various layers of materials, like PVC, help seal the roof, making it leak-proof. And recycled sneaker soles aid filtration of rainwater. The tour video makes the system seem so simple and brilliant. But one reason we don’t see more green roofs is because they need to be properly fortified to hold up the extra weight of a garden plot. The work it takes to do that, and the cost, can sometimes be daunting.
But PHS plans to start quantifying the energy and rainwater savings someday soon to prove these structures to be worthwhile, and I’m willing to bet there will be significant results. Until then, I’m more than impressed with the near acre of carefree sedums, which felt like massage balls under my toes. And the noticeably cooler air.
Growing Where Planted: Check out the following links for more information on green roofs and green walls