Green Roofs

What is a green roof? A green roof is a living, vegetative roofing alternative to the standard, nonpermeable roofs traditionally found on buildings. Also known as roof gardens or eco roofs, green roofs are popular in Europe, particularly in Germany, and offer a multitude of architectural, environmental and aesthetic benefits. They promote environmental protection in a variety of ways, reduce energy and maintenance costs, and enhance the aesthetic appeal of a building. Green roofs offer a way of lessening the impact that a construction site has on the land by replacing some of the environment that was displaced by the building.

Greenroof technology requires an understanding of and detailed knowledge of plant biology, hydraulic engineering, and architecture. The green roof system is a series of waterproof membranes and drainage layers, topped with gravel and soil, into which carefully selected plant species, such as sedum, are planted. They are living, dynamic systems, incorporating nature into building design, which can become net producers of energy, clean water and air.

Green roofs can be intensive or extensive; intensive green roofs are designed to be walked on, and can include features like benches and paths. The structural load for an intensive green roof is much heavier than for an extensive green roof.

A green roof helps to clean and manage storm water. The control of storm water runoff is achieved by mimicking natural processes by intercepting and delaying rainfall runoff with the roof plant communities. The plant diversity provides for plant uptake of the water, and friction slows the water down, which helps to retain the water on the green roof surface. They help reduce the total volume of storm water going into streams, thereby reducing problems such as sediment transport, soil erosion, and run off of pollutants into streams.

Green roofs help reduce air pollution by filtering and binding dust particles and airborne toxins as well as removing carbon dioxide from the air.  They create a livable habitat for birds, butterflies, and other forms of animal life. They also help to reduce the negative impact a building has on a site by reducing heat island effect, or hot spots, that commonly occur in an urban setting.

Harford Community College plans to install two green roofs on Joppa Hall during its 2004 reconstruction. For updates on this project, visit the Green Building updates in the Accomplishments section of this web page often.

To learn more about green roofs in general, visit this very informative web site: www.greenroofs.com.