Green (or sod) roofing is held up as a technology that offers a myriad of benefits for buildings as well as the general public, but perhaps it can now be labeled as recession-proof.

The non-profit green roofing industry group, Green Roofs for Healthy Cities (GRHC) in Toronto, Canada, says a recent survey of its corporate members revealed that the green roofing industry grew by 16.1% in 2009, even while other areas of the construction market and the economy foundered.

“Despite this fantastic progress, opportunities for future annual growth are enormous, with green roofs accounting for an estimated 10 million square feet annually in an overall flat roofing industry which replaces or builds more than 4 billion square feet in North America annually,” said Steven W. Peck, founder and president of GRHC, in a statement.

Moreover, the group’s annual Top Ten Cities List indicates that for the sixth time in a row Chicago led the nation with more than 562,000 square feet of sod roofs installed, followed at a distance by Washington, D.C., and Minneapolis.

“We are definitely seeing the emergence of more public policies and direct investment that support the implementation of green roof infrastructure due to its many public benefits, such as stormwater management, air quality improvement, and reducing the urban heat island effect,” said Jeffrey L. Bruce, chair of Green Roofs for Healthy Cities.

As its name suggests, a green roof is one that consists of several layers of protected membranes and soil medium, and planted with any type of vegetation, including succulents, grasses, and other plants. It offers sound insulation for the building, promotes energy efficiency, and is said to help keep the interior of a house or building cooler.

But in addition to the benefits for the building, green roof proponents say the installations help society as a whole. It cleans the air, takes the stress off sewer systems through stormwater retention, and helps reduce the heat island effect that makes urban temperatures climb in the summer.

“Through the daily dew and evaporation cycle, plants on vertical and horizontal surfaces are able to cool cities during hot summer months,” the GRHC says on its website. “In the process of [taking water from the air and then evaporating it through their leaves], plants use heat energy from their surroundings when evaporating water.”

These attributes are the reasons more jurisdictions/cities have been interested in promoting green roof installations either in retrofits or new construction. Chicago, which is the foremost American city for green roofs, made the technology part of its commitment to green back in the early 2000s, and it’s reported that Mayor Richard Daley launched the green roof movement in the city after seeing installations in Europe.

As an example of the technology’s benefits, the City Hall building was outfitted with a sod roof and is reportedly 14 degrees to 44 degrees cooler on a summer day than the county office building across the street, which has a typical black-tar roof.

In addition, a 2005 Green Roof Grants Program has helped dozens of green roof projects throughout Chicago. At present, the city leads the nation with more than 200 green roofs that cover almost 3 million square feet.

Washington, D.C., which has been pushing green roofs as well, ranked second in 2009 with 190,377 installed square feet. Earlier this week, the city hosted the Regional Green Roofs & Walls Conference and Training, where attendees and panelists focused on how to achieve a higher level of green roof adoption in D.C. to meet a target of 20% green roof coverage by 2020.

Nigel Maynard is senior editor, products, at BUILDER magazine.

Top 10 Cities For Green Roofs

1. Chicago
2. Washington, D.C.
3. Minneapolis
4. Baltimore
5. Newtown Square, Pa.
6. New York
7. Redmond, Wash.
8. Montreal, Quebec (Canada)
9. Quebec City, Quebec (Canada)
10. Milwaukee

Source: Green Roofs for Healthy Cities

Learn more about markets featured in this article: Washington, DC, Chicago, IL, Minneapolis-St. Paul, MN, Baltimore, MD.