Green Roof Primer
A €œgreen roof system€ is a roof designed to support a layer of soil and plants on the roof surface. Green roofs have several aesthetic and practical advantages.
- Improved Heating and Cooling Efficiency
- Double the Life of the Roof Membrane
- Greatly Reduced Storm Water Runoff
- Sound Dampening
- Visually & Psychologically Appealing
- Reduced Heat-Island Effect in Urban Areas
Green roof systems are classified as "intensive" or "extensive".
An intensive green roof has more than six inches of soil material and can generally support plants and trees without additional watering.
An extensive green roof has less than six inches of soil material and can only support drought tolerant plants, unless it is watered during the Summer.
Engineering
Green roof systems are substantially heavier than a conventional roof. A stronger support structure is therefore required. Intensive green roofs are commonly supported with steel-reinforced concrete decks.
Extensive green roofs add about 5 pounds per square foot per inch of soil depth and are typically supported with a truss system.
For a typical 4 inch deep extensive green roof, the additional dead load is about 20 pounds per square foot. Wood trussing is quite suitable for this task and has numerous benefits over steel trussing.
Economic Advantages
For developers, the primary advantage to incorporating a green roof system into the building design is reduction in stormwater management costs.
Many cities such as Chicago, Washington, DC and Asheville, NC are actively encouraging green roof construction as a means to reduce stormwater runoff and combined sewer overflows. Other municipalities are encouraging green roof development with tax credits, density credits, or allowing a small impervious credit to be applied to other structural BMP requirements.
Green Roof Design Firms
The following design firms specialize in green roof systems in the United States*:
Living Roofs, Inc.
Emilio Ancaya
Asheville, North Carolina
828-252-4449
http://www.livingroofsinc.com/
The Ecobuilders
Rob Moody
828-254-3334
Asheville, North Carolina
http://www.theecobuilders.com/
Fredrick Stewart Architects
Fredrick Stewart
Raleigh, NC
919-563-4284
http://www.fredrickstewart.com/
Roofscapes, Inc.
Nate Johnson
Philadelphia, Pennsylvania
215-247-8784
http://www.roofmeadow.com/
W.P. Hickman, Inc.
Tony Nista
Ohio
440-479-0339
http://www.ecoroofsystems.com/
MacDonald Environmental Planning, P.C.
1022 SW Salmon Street
Suite #222
Portland, Oregon 97205
Ph: 503.224.1225
http://www.mep-pc.com/
*Placement in this list does not constitute an endorsement of this firm by Dominion Truss. This is merely an informational list.
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