Home
Special Reports
 
Back
 
Plant a Green Roof


By Katherine Noyes
Charity Guide
2005


By creating a green roof layered with soil and plants atop your house, you
not only add natural beauty to a landscape increasingly dominated by
concrete and pavement. You also help reduce the urban "heat island"
effect, by which cities tend to be several degrees hotter than surrounding
areas, and you provide a roof-garden habitat for insects, songbirds and
other wildlife.

Unlike the natural green areas that once covered the earth, most cities
and suburbs are made primarily in shades of gray and black. Functional as
they may be, the asphalt roads and tar roofs responsible for those drab
colors also cause a host of problems:

These manmade materials soak up the sun's radiation and reflect it
back as heat, making cities at least 7 degrees hotter than surrounding
areas. On Chicago's City Hall, by contrast, which features a green
roof, temperatures on a hot day are typically 25 to 80 degrees cooler
than they are on traditionally roofed buildings nearby. If all the
roofs in a major city were "greened," urban temperatures could be
reduced by as much as 12 degrees.

The impermeable quality of traditional building materials makes storm
water a problem, since there is nothing to prevent rainwater from
rushing off rooftops, collecting pollution and heavy metal
contamination along the way, and then overburdening urban sewage
systems. Green roof strategies have been found to hold the pollutants
in their soil while retaining up to 75 percent of the water and
subsequently allowing it to return to the atmosphere through
evaporation.

Concrete landscapes also offer nothing to support the insects, birds
and other wildlife that depend on vegetation to survive. Much like
planting native gardens and backyard habitats, roof gardens can
complement wild areas by providing "stepping stones" for songbirds and
other wildlife facing shortages of natural habitat. Even in high-rise
urban settings as tall as 19 stories high, it has been found that
green roofs can attract beneficial insects, birds, bees and
butterflies.

Sometimes known as "living roofs" or "eco-roofs," green roofs have also
been found to extend roof life and to reduce heating and cooling costs
dramatically.

Create a Green Roof on Your House

Green roofs are typically installed on flat roofs, but can be adapted for
sloped roofs as well. They can be either "intensive," with about 12 inches
of soil and a wide variety of plants, or "extensive," with about 3 inches
of soil and a more limited selection of suitable plants. Extensive green
roofs are less expensive, lighter, and easier to maintain. You should
speak to a structural engineer or architect to assess an existing roof
before making plans to convert it into a green roof.

How-to information, products, services and do-it-yourself kits are
available from:

Greenroofs.com
ELT Easy Green GreenRoof Systems
Green Roof Plants
Roofscapes
Green Roof Solutions
Green Roof Tops
BBC Gardening
Green Roofs for Healthy Cities

A directory of green-roof experts and professionals is available at
Greenroofs.com, and other suggestions and green roof links are available
at Earth Pledge and Emery Knoll Farms.

Green Your Community

There are many examples of community efforts to create green roofs on
shared buildings, including some notable projects in Portland. A
searchable database of green-roof projects throughout the world is
available from GreenRoofs.com and volunteer opportunities abound.
To initiate a green roof project yourself, begin by asking building owners
in your community to investigate the possibility of greening their
rooftops. Sample letters are available from Greening Gotham.


 

Promoting Green Building Design, Construction and Operation, Sustainable Living,
Clean Technology, Renewable Energy Resources and Energy Independence