Plant a Green Roof

 By creating a green roof layered with soil and plants atop your home, 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 green roof-enhanced City Hall, by contrast, temperatures on a hot day are typically 25 to 80 degrees cooler than they are on traditionally roofed buildings nearby. The economic benefits can be considerable: On a one-story building with a green roof, for example, cooling costs can be reduced by between 20 and 30 percent.
• 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 pollutants in the soil while retaining more than 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 been found to benefit the planet--and all its inhabitants--in many ways.

Create a Green Roof on Your House

Green roofs are typically installed on flat roofs, but they 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. A savings calculator is available from GreenRoofs.org. 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
• Greenroofs.org
• ELT Easy Green GreenRoof Systems
• Green Roof Plants
• Roofscapes
• Green Roof Solutions
• BBC's Gardening Guides
• Green Roof Tops

A directory of green-roof experts and professionals is also available at Greenroofs.com; a video on YouTube demonstrates the green roof premise in action.

Green Your Community

There are many examples of community efforts to create green roofs on shared buildings, including some notable projects in New York, Chicago and 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. A sample request for proposals is available on GreenRoofs.com.