Green Roof

Green roofs have a history spanning millennia, from the legendary Hanging Gardens of Babylon to the traditional sod roofs of Scandinavia, but the modern green roof industry emerged in Germany in the 1960s and 1970s when researchers began systematically studying vegetated roof systems for their stormwater management and insulation benefits. Today, Germany alone has over 80 million square meters of green roofs, and cities worldwide including Toronto, Copenhagen, and Portland have adopted green roof requirements or incentives for new construction. The technology consists of a waterproof membrane, root barrier, drainage layer, growing medium, and vegetation, assembled in layers that protect the building while supporting plant life. Green roofs are broadly categorized as extensive systems with shallow soil supporting sedums and grasses, or intensive systems with deeper soil capable of sustaining shrubs, trees, and even full gardens. For residential applications, extensive green roofs are more common due to their lighter weight, lower maintenance, and reduced cost. The benefits are substantial and multifaceted: green roofs reduce stormwater runoff by 50 to 90 percent, lower cooling costs by shading and evapotranspiration, extend roof membrane life by protecting against UV degradation and temperature extremes, reduce the urban heat island effect, and provide habitat for pollinators and birds. Aesthetically, they transform an otherwise utilitarian surface into a living landscape visible from upper floors and neighboring buildings.