I went to a lunch and learn at Greenable (the Philadelphia green building supply store) on Monday. I've been attending their monthly educational lectures because I'm doing research for both my writing and the addition that we are planning for our house next year. We want to make our home as energy efficient and sustainable as we can afford. One of the things my husband and I have been talking about is a green roof.
A green roof is a roof on a building that has been covered with vegetation. There's a lot more to it than just sticking some dirt on top of your roof and throwing down some seeds. A proper green roof has several layers starting with the roofing materials and then waterproofing materials, drainage materials and others are layered on top of the roof before the vegetation is planted.
There are many environmental benefits to a green roof. Here are some of them that I learned at the lecture.
- It increases storm water retention which produces a cooling effect to the air around as the water slowly evaporates.
- It improves air quality around the building.
- It reduces low level ozone.
- It can reduce energy costs in a building up to 30% because the roof is not absorbing heat and holding onto it. The heat is released when the sun goes down.
- Urban wildlife habitats are created with some green roofs.
- The roofing materials under the vegetation last much longer than exposed roofing materials. They last longer and that keeps roofing materials out of landfills.
It seems, however, that in the U.S. these types of roofs are predominately being put on large buildings, not residences. If we want to do a green roof on our addition, it will probably be very costly because we'd have to have it specially designed. It's not that it can't be done. It's just that no one's doing it right now. Perhaps we'll have to find another way to make our addition sustainable, but we haven't completely ruled it out yet.
Have you ever seen a green roof? Where was it?