Benefits of Green Roofs
Green roofs help with stormwater management.. They retain a portion of the rainfall they capture but at the same time, they also slow the flow of water that does come off the roof. These effects minimize the amount of water rushing from the rooftop into the storm sewers and ultimately into the bodies of water that collect that water.
The waterproofing material on a normal roof will degrade over time. It will have to be replaced every 15 or so years. This degradation is caused by two factors: photodegradation from sunlight and mechanical degradation from temperature extremes. However, no sunlight reaches the membrane beneath a green roof. And the temperature extremes that are typically experienced and greatly moderated by a green roof. A black roof can undergo summer day/night temperature extremes of well over 100 degrees Fahrenheit. It is this regular expanding and contracting from temperature that causes the failure in many roofs. Beneath a 4″ green roof, the same membrane would experience a temperature swing of less than 10 degrees. An example of this longevity is a green roof installed in Portland, Oregon has been functioning leak free since 1975.
Green roofs help reduce the flow of heat into and out of the surfaces they cover. This leads to lower energy costs.
Urban Heat Island effects comfort of city residents as well as public health. City green spaces such as parks, tree-lined streets and green-planted areas are cooler due to evapotranspiration (evaporation plus the transpiration of the plants releasing moisture through photosynthesis). Research suggests that any increases in urban green space, including green roofs, will help mitigate the Urban Heat Island Effect.
Green Roofs are not similar to native landscapes. Yet, they attract a number of insects and birds. Native bees and honeybees love the pollen from Sedum and Delosperma. Many butterfly species can be spied on green roofs.
Greenroofs are aesthetically...