Stormwater Source Control Design Guidelines 2005 - Waterbucket

Green Roof Stormwater Source Control Design Guidelines 2005Green roofs provide multiple benefits, including:ooooooooooReduction in stormwater peak flows.Reduction in rainfall volume leaving the roofdue to evaporation and evapo-transpiration. Atypical extensive green roof of about 75mm ingrowing media can be designed to reduceannual runoff by more than 50% (Miller,2001b; FLL, 2002).Mitigation of the urban heat island effect,which is raising the temperatures of cities andincreasing energy use as well as increasing theeffects of air pollution (Peck & Kuhn, 2001).Air filtration, removing fine particulates fromthe air (Peck & Kuhn, 2001).Reduction in heat gain and the need for airconditioning in the summer – modeled savingsare as high as 25% (Peck & Kuhn, 2001).Reducing heat loss in the winter; studies showthat with 30 cm of growing medium, rooftemperatures do not drop below 0ºC evenwhen outside temperatures are -20ºC (Peck &Kuhn, 2001).Roof membrane protection and life extension.European studies have revealed that greenroof installation can double the life span of aconventional roof, by helping to protect themembrane from extreme temperaturefluctuations, ultraviolet radiation, andmechanical damage (Peck & Kuhn, 2001).Sound insulation – tests show that 12 cm ofgrowing medium can reduce sound by 40 db(Peck & Kuhn, 2001).Increasing biodiversity in urban areas byproviding habitat for birds, insects, nativeplants, and rare or endangered species.Aesthetic value and increased urban greenspace.64Greater Vancouver Sewerage & Drainage District