Study Evaluates Benefits of Green Roofs

SEATTLE-Green roofs are being installed on four different privately owned Downtown buildings here as part of an effort to quantify their effectiveness in reducing storm water runoff in the region. The Seattle Green Roof Evaluation Project is being spearheaded by Magnusson Klemencic Associates (formerly Skilling Ward Magnusson Barkshire), a locally based international engineering firm with a sustainable design division. The 18-month Seattle Green Roof Evaluation Project will measure the impact of green roofs on storm water runoff, including reduction in rainfall entering conventional storm water management systems. The volunteers for the project are Unico Properties’ Rainier Square at 1301 Fifth Ave., Sellen Construction’s headquarters at 227 Westlake Avenue N., Gregory Broderick Smith Real Estate’s Stadium Center building at 801 First Ave. S. and a Vulcan Inc. building at 2201 Ninth Ave. Sellen also brokered green roof materials and built the roof plots. Teufel Landscaping donated soil and plants. Rainier Square, the low-rise retail portion of Rainier Tower will be the only project site to offer close-up, unescorted public viewing. It will also be the only roof to receive a sample green roof planted on both 2- and 4-inch platforms. “We see this as a clinical trial that may confirm and quantify the benefits of green roofs,” says Unico CEO Dale Sperling. “We believe there is great value in ‘green’ solutions that enhance existing and future buildings and improve the urban environment.”MKA’s impetus for the project was the distinct lack of existing green roofs in the Downtown market despite the well-publicized benefits and Seattle’s rainy climate. Indeed, only two Downtown buildings have green roofs, and both of those are atop publicly financed projects (Seattle Justice Center and Seattle City Hall). Moreover, a MKA says a recent sampling of 13 projects that proposed green roofs revealed that, due to its cost being 50% to 100% more expensive than a conventional roof, none of them ever followed through with the project.”The Seattle Green Roof Project hopes to change those numbers by demonstrating green roof applications on commercial buildings and quantifying their environmental benefits in Seattle’s climate,” states MKA in an electronic brochure on the project. “It is hoped that further understanding of green roofs will hasten their implementation and enable city policymakers to consider appropriate incentives for their use.” Green roofs do more than just decrease storm water runoff but since storm water runoff is the most measurable of the touted green roof benefits, it is the most logical place to start, according to those involved in the project. Green roofs also have been credited with extending the life of roofing materials by blocking ultraviolet light and minimizing roof expansion and contraction. Green roofs are also credited with improved building insulation, reduction in noise levels and cleaner runoff. While Seattle doesn’t yet offer any incentives for green roofs, Portland, OR, offers incentives such as FAR bonuses, the City of Minneapolis is in the process of implementing incentives and the City of Chicago actually mandates the use of green roofs. Meanwhile, California and Maryland have incentives that help offset costs and Massachusetts and Pennsylvania reportedly have similar legislation in the works.