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In 2007, 30 percent more green roofs were installed in North America, the Green Roofs for Healthy Cities' 3rd Annual Green Roof Market Industry Survey said. According to corporate members of Green Roofs for Healthy Cities, the finding represents a five percent increase over 2006's annual market growth rate of 25 percent. The survey is based on square footage of green roof projects installed by GRHC's corporate members in 2007.

The top three cities on the Top 10 U.S. Cities list includes: No 1: Chicago, No. 2: Wilmington, D.E., and No. 3: Baltimore.

The city of Chicago remains the number one city for the fourth year in a row with over half a million new square feet of green roofs installed in 2007, evidence of the city's commitment to becoming America's greenest city through green roof policies and incentives that support green roofs, walls and other forms of living architecture.

Newcomers to the list include: Brooklyn, N.Y.; Virginia Beach, Va.; Royersford, Pa.; Philadelphia, Amery, Wisc.; and Germantown, Md.