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Green roofs are multi-functional roofng systems that provide signifcant economic and environmental benefts. Green roofs mitigate the impact of urban development by managing stormwater, reducing building heat absorption, and creating valued green space . Filtrexx ® GrowingMedia tm may be utilized as an important component of the green roof soil media for a successful green roof installation.

Green roof systems can have a variety of objective applications including: storm water runoff reduction, storm water pollutant reduction, thermal buffering of the building envelope to save energy in cooling and heating, creation of urban wildlife habitat, creation of human recreational green space, air pollution mitigation, and/or mitigation of heat island effects in urban areas. Green roof systems have been used in Europe for centuries, the frst systems appeared as grass or sod roofs that provided thermal insulation in Northern Europe. The engineered green roof systems we use today began to appear over thirty years ago in Germany. Today they are widespread throughout Europe and are becoming common throughout the United States. All green roof systems utilize the following components:

• High-quality impermeable waterproofng membrane covering the roof structure. • Drainage layer.

• Lightweight growing medium layer. • Vegetation.

There are many commercially available green roof systems that vary only slightly. Some systems utilize a drainage layer that unrolls into one continuous cover over the waterproofng while other systems utilize interlocking trays or grids that are combined to create a continuous drainage layer. Additional components, such as root barriers, are also used in some systems. Green roofs may be divided into two broad categories, intensive and extensive. Intensive green roof systems generally consist of a deep (6 in+, 150mm+) soil layer and vegetation that may include groundcovers, turf grass, shrubs and trees. Extensive green roof systems have a shallow (1-6 in, 25-150mm) soil layer and only hardy, drought-tolerant groundcover vegetation. Extensive systems are less expensive, lighter weight, lower maintenance and more common than intensive green roof systems. Green roof systems may be installed during new building construction or retroftted onto an existing building. Extensive green roof systems are feasible on roofs with up to a 30° slope. The key consideration for extensive systems is whether the roof structure is adequate to hold the weight of the green roof. Extensive green roofs can weigh 12-50 lbs/square ft. (59-244 kg/square m), and intensive roofs often way over 50 lbs/square ft (244 kg/square m). Consult a structural engineer to verify the roof and building structure is adequate before installing any green roof system.

Green roof soils are typically engineered to be very lightweight. They are primarily made of inorganic components such as expanded slate and shale, and extruded clay and perlite, which provide