Green roof systems...we are hearing about them more and more. Whether it be for commercial uses or even residential green roof design, green roof technology is speeding ahead. Germany has been using them for many years now.
There are a variety of plants that can be used. Sedums are extremely common due to their shallow root system. In addition, meadow grasses and perennials can be used. Trees, too, can be part of a green roof system. The types of plants utilized will depend on the type of green roof being installed. Full coverage will take about two years.
Green roofs are also called eco-roofs or living roofs. If you were to look at a cross section of a green roof system, you would typically see the following layers (from top down):
However, not all green roof installations are done in the same way or contain the same layers. It can depend on many things. There are lightweight systems for shallow plants and there are also heavier systems for plants with deeper roots....even trees.
Green Roofs and Storm Water Management Benefits
A green roof can do many positive things for our environment.
Green roofs control storm water runoff by allowing the water to seep into the plant roots and soil. With the standard roof, water from the roof must be channeled to an acceptable area. If not done correctly erosion can occur, along with pollution.
Roof Life is Extended Tremendously
Urban Heat Island Effects are Greatly Improved
Most roofs are made of a dark color and can reach temperatures of 150 to 190 degrees. In urban areas, temperatures can be 2 to 10 degrees hotter than those in rural areas.
So how do green roofs help this situation?There are a few different ways:
Evapotranspiration (it's not that complicated...read on!)
Moisture is retained in the roots of the plants. The plants then absorb this water, which then evaporates through the leaves. This cools the air above the roof surface.
Thermal Mass Effect
Large amounts of heat can be absorbed and stored by a green roof. While normally, heat from the roof is transposed to the building interior, with green roofs, the heat can be absorbed and stored there. The heat is released once the air cools down. This eliminates building temperature extremes, reducing cooling demands.
Plant foliage can actually provide shade, which also helps to cool the roof.
Additional Benefits of Green Roofs
"Susan, what a pleasure it was to work with you. You made me feel like I was your only client - responding late at night and always so quickly! Your design is amazing and we only hope we can do justice to it when we plant. You have such fantastic ideas and you are so open to suggestions and changes. Loved working with you - now if you could only come to Canada and plant it!!!"
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