Raise the eco-bar of your roof: use your rooftop as another garden and do great things for the planet.

Author:Ancaya, Kathryn
Position:DIGGING IN
 
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Green roofs are often referred to as living roofs, eco-roofs, vegetated roofs and garden roofs. The names themselves Begin to describe what a green roof is: a roof that is alive with plant material. The benefits of green roofs are most pronounced in urban areas and over large rooftops; however, they are still capable of providing many of the same economic and environmental benefits, as well as less measurable results like social benefits and beauty, On a smaller scale [for a local example of a green roof, turn to page 34].

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What makes Up a Green Roof?

A green roof is, at a minimum, composed of a waterproofing membrane, root barrier, drainage layer, lightweight growing medium and plant material. This assembly of material can be constructed on any properly designed or existing roof that meets the structural requirements of the system, which are determined by the weight of the above components.

Green roofs are broken into three categories: extensive, semi-intensive and intensive. The growing medium depth determines the category of green roof and therefore the diversity and type of plant material. Extensive green roofs typically have two to four inches of growing medium and support low-lying, drought tolerant plants like Sedums and other succulent species. Semi-intensive green roofs typically have 6-10 inches of growing medium and can support a more diverse plant palette, including drought tolerant grasses and perennials as well as succulents. Intensive green roofs are similar to a natural planting or garden in that they're designed to hold many feet of growing medium. As a result, intensive green roofs can support a wide variety of plant material, such as perennials, shrubs and even trees.

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Why a Green Roof?

For the individual building/home owner, the advantages include significant energy savings from reduced thermal loading in warmer months, your space will stay cooler, thereby reducing the need-for air conditioning. Additionally, there are reduced costs associated with roof replacement, as waterproofing membranes under green roofs last two to three times longer than traditional roofs that are exposed to continual UV light and fluctuating temperatures. On a larger scale, the benefits of green roofs include the above, as well as a 65-100 percent reduction of stormwater runoff, improved water quality of that runoff, increased urban...

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