According to the non-profit association Green Roofs for Healthy Cities, North American green roof infrastructure implementation increased from 1.3 million square feet in 2004 to 2.5 million square feet in 2005, an increase of 72 percent.
The organization reports that the top 10 cities by square footage planted in 2005 are as follows: Chicago; Washington, D.C.; Suitland, Md.; Ashburn, Va.; New York; Culpepper, Va.; Austin, Texas; Arlington, Va.; Des Moines, Iowa; and Ottawa, Ontario, Canada.
Green roofs, which largely are used for stormwater retention, can be installed for as little as $9 per square foot, experts say. The resulting increased property value, energy cost savings, and a longer life for the roof can offset the investment.