A school and library in Omaha are the first of a movement to green city rooftops to improve the health of their cities.  Additional structural support, leak-proof membranes and special soils must be used to develop a rooftop garden, but the cost of this is far outweighed by the benefits of improved temperature control, lower energy consumption and improves storm water absorption.  Modern materials also make it possible to install a leak-free roof that will last the lifetime of the building.

In Lincoln, where the Pioneers Park Nature Center installed a native-flora roof in June, the advantages of going green quickly have become apparent, said Richard Sutton, the landscape architect who designed and continues to monitor the roof.

"It's like a giant sponge up there," absorbing storm-water runoff and Nebraska's summer heat, Sutton said. When traditional roofing reached temperatures of 140-plus degrees last summer, he said, the nature center's green roof remained a comparatively cool 80 to 90 degrees. That makes a big difference in the cost of cooling a building, he said. In the winter, green roofs provide insulation against heat loss inside a building.

The public still thinks of green roofs as an oddity, Sutton said. But the nature center's roof, unusual because of its reliance on native plants, is quickly becoming an ecological and environmental success, he said.

"It's exceeded my wildest dreams," Sutton said.

» Omaha World-Herald