Green-Roof Study Results Offer Positive Surprises

摘要

A green roof has the potential to lower stormwater runoff from 65 to 94%. In cities with com-bined sewer systems, that translates to a significant reduction in the demand placed on wastewater treatment plants during storms, according to a two-year study of green roofs in Seattle. In addition, green roofs allow building owners to reduce the size of stormwater detention tanks needed for peak rainfall. That can offset the cost of a green roof by 30 to 60%, according to Magnusson Kle-mencic Associates, the local engineer that led the $125,000 green-roof evaluation project. The study quantified the effectiveness of green-roof stormwater management, based on rainfall and weather conditions, from July 2005 through this January.