Green Roofs

This is the view from one of the third floor windows of the building. Yesterday, the folks from David Brothers Landscape Services finished putting the plants on the roof. Yep, those are plants on the roof.

On top of the roof surface, David Brothers put about 4-6 inches of soil and rock to create a bed for planting. Then they planted a variety of grasses and a low-growing plant called Sedum. The combination makes what is called a "green roof."

We included green roofs on a small part of the building primarily because we think they're so cool to look at and they give a great teaching opportunity. We made a decision to dedicate the bulk of the roof to capturing rainwater for the toilets and irrigation. But we thought a small nod to green roofs was really needed given the unique nature of the community. The benefits to us and the community we serve of a green roof are:

• An estimated 30 percent reduction in the amount of cooling needed to keep the space underneath comfortable in summer months. Our green roofs are too small for this to make a big difference, but every little bit helps.
• There will be almost no stormwater runoff from the green roofs. The soil and the vegetation should absorb virtually all of the rain that falls on them. Stormwater runoff is a major source of pollution in the Schuylkill River watershed (because of the "stuff" that the stormwater picks up on the way to the river).
• No one really knows how much this extends the life of the roof membranes. If you think about it, what causes the rubber roofs to deteriorate is mostly the exposure to sunlight. These roofs will never see any sunlight.
• The roofs lower the "heat island" effect that buildings cause in cities. That refers to the fact that the black roofs in cities get very hot. That hot air rises. It's a very inhospitable environment for birds. We won't be surprised to see a bird's nest (or two even) on our small roofs.

So, for a lot of good reasons, both environmental and economic, green roofs frequently are a better choice. And you have to admit....that's a nice view.