Why Green Roof Systems Are Environmentally FriendlySusan Schlenger
January 1, 2005 — 1,187 views
Green roof systems seem very complicated, don't they? You might be wondering how they get installed, or where they can be used. Then again, what plants actually grow on a roof? And what is all the fuss about?
The nuts and bolts is that green roofs are very good for the environment. Because plant material is the top roof layer, instead of typical roofing material, many positive situations are created. Here are some of them:
Roof water is absorbed by the plants which serve as wonderful water collectors. This is great for stormwater management. Instead of the water becoming a problem as to where it will drain to, much of it goes directly to the plant roots where it is utilized. The little that does drain away does so slowly. Less water runoff means less erosion and less pollution. The plants absorb and temporarily retain roof heat, releasing it into the atmosphere as temperatures cool. This keeps the inside of buildings and homes cooler, reducing air conditioning needs and costs.
Green roofs extend the life of the roof. There is less debris damage. There is also less roof expansion and contraction from temperature changes. Some roofs with green roof construction can last 50 years.
These eco-roofs create new wildlife habitats. Yes, birds will appear there!
Germany has been using green roofs for over 35 years, and now some U.S. cities are promoting green roofs.
Green roofs are created in layers. Different applications require various green roof construction. Some are more light weight, while others are more of a mid weight. In addition, there are actual roof tops with more intricate construction able to support trees. Sedums, wildflowers, and perennials are all common green roof plants.
Typically though, the layers of a green roof system would contain plants, growing medium, filter fabric, drain, insulation, root barrier, and a waterproof membrane. As mentioned this can be different for different situations.
Green roofs generally do not need irrigation. If some is needed, however, the water should be delivered directly to the roots.
Both flat roofs and those that are sloped can accommodate green roof systems. There is a maximum slope for pitched roofs.
The appearance of green roof tops for residential applications and also for commercial greatly improves the aesthetics of our landscapes. As I looked out my upper floor window the other day, I couldn't help thinking how nice it would be to look at plants and greenery instead. Likewise, in urban areas, the upper view streetscapes would be unbelievably improved.