Sustainable Facility - February 2009 - (Page 16) spotlight FIRESTONE BUILDING PRODUCTS Garden Roof Grows to Keep Costs Down. Reducing storm water run-off, increasing cooling system efficiency, extending the roofing system’s useful life and attaining certification as a LEED (Leadership in Energy and Environmental Design) project were key factors leading to the selection of a garden roofing system for the Rapid Central Station transit center in Grand Rapids, Mich. Built by the Interurban Transit Partnership (ITP), the new facility features a 15,600-square-foot Firestone Garden Roofing System comprised of a fully adhered RubberGard EPDM membrane with an overlay of Xero Flor, a unique green roofing technology. The lightweight, lowmaintenance roofing system permits vegetation to grow directly over protection layers of a root barrier and moisture retention mat, increasing energy conservation and improving water management. “One of the goals we achieved in building this facility was becoming the first LEED-certified transit center in the country,” explained Anne Laurent, project architect, Progressive AE, Grand Rapids. “With so much asphalt and concrete construction, it was nice to create a project that could contribute to improved air quality, reduce rooftop heat gain, and provide a habitat for birds and insects.” 16 S U S TA I N A B L E F A C I L I T Y F E B R UARY 200 9 GREEN BUILDING MOVEMENT The LEED Green Building Rating System is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings. With increasing awareness and emphasis of sustainable building, as well as the rapid adoption of LEED by the North American construction industry, garden roofing systems that have been widely used in Europe for several decades are becoming more prevalent. To minimize roof maintenance, add aesthetic appeal and obtain LEED certification, Progressive AE opted to use a garden roofing system on approximately 60 percent of the new structure, which covers the Rapid Central Station’s information and conference center. A fully adhered Firestone RubberGard EPDM Roofing System protects the rest of the facility over a concrete deck. To install the garden roofing system, J&L Roofing of Grand Rapids first attached tapered Firestone ISO 95+ polyiso insulation ranging from 0.5 inches to 10 inches to the steel deck, followed by an additional 1.5-inch layer of polyiso and a protection board. The contractor then fully adhered 60-mil RubberGard EPDM membrane to the board. A protection fabric, drainage board and moisture retention mat were installed over the EPDM membrane, in preparation of the Xero Flor planting substrate. The garden roofing system consisted of a hardy variety of sedum with a non-aggressive root system. Xero Flor was pre-cultivated at ground level to reduce installation time and provide instant coverage when installed, rather than establishing the vegetation layer on the roof. Following final inspection, Firestone Building Products warranted the roofing system for 20 years. SMALL, YET MIGHTY Although the garden roofing system is less than two inches thick from root barrier through the planting substrate, it offers outstanding storm water management because it retains 60 to 100 percent of the rainfall it receives. The system also mitigates the “Urban Heat Island Effect,” and decreases air conditioning costs, by acting as barrier to the thermal transfer of the sun’s energy to the roof. And, the natural system increases the overall roof membrane lifespan by moderating temperature extremes on the roof surface and minimizing stress caused by temperature fluctuations. While broad use of garden roofs in the U.S. may be years away, the environmental impact and aesthetic advantages on facilities like the Rapid Central Station are paying dividends today. 800-428-4442 www.firestonebpco.com http://www.firestonebpco.com
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