(FORTUNE Small Business) – Talk about a growing business: Roofscapes installs rooftop gardens, which offer more insulation than traditional coverings. Green roofs cost more but last longer, claims Roofscapes founder and principal Charlie Miller. The Philadelphia firm has planted green roofs at Chicago City Hall, saving $3,600 a year in heating and cooling costs, and at Life Expression Wellness Center (above) in Sugar Loaf, Pa. Come 2006, it plans to unveil its biggest project: the 350,000-square-foot roof of Howard Hughes Medical Institute in Ashburn, Va. —MATTHEW PHAN