BY JAMES S. TYREE Published: April 23, 2010
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NORMAN — The National Weather Center introduced the state’s first "green roof” Thursday to help celebrate Earth Day.

The roof atop the University of Oklahoma research campus building has 160 trays measuring a combined 1,280 square feet that will hold plants and grasses planted in layers of clay, sand and organic material that have one-third the weight of regular soil.

Reid Coffman, an OU landscape architecture assistant professor, said the green roof, also called a vegetative roof system, is designed to drastically reduce both storm water runoff and energy use and cost.

"These have been shown, depending on conditions, to produce 25 to 75 percent in annual air conditioning savings,” said Coffman.

Small sprouts can be seen in some trays while others are barren. Coffman said most trays will be filled with sedum plants, which have shallow roots that are ideal for the trays’ four-inch depth.

Native grasses and perhaps wildflowers will be planted in the empty trays.

Second site planned
Rainfall will absorb into the substrate of clay, sand and organic material instead of running off the roof, and the numerous plants that will cover the roof will interrupt solar radiation and keep the building cooler.

The green roof trays are expected to stay three years atop the National Weather Center’s classroom deck for observation and research, Coffman said.