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