A green roof is a roof fully or partially covered in plants and waterproof media that helps reduce the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater release, and promoting evaporation.
A green roof is a fully or partially vegetated roof. The system is composed of multiple layers, including waterproofing, a drainage layer, a planting media, and special plants. These systems can be installed on many types of roofs — from small slantings to large commercial flat structures. Two basic types of green roofs have been developed: extensive and intensive. An extensive green roof system is a thin, lighter-weight system predominantly planted with drought-tolerant succulent plants and grasses. An intensive green roof is a deeper, heavier system designed to sustain more complex landscapes. A green roof is effective in reducing the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater release into the combined sewer system, and promoting evapotranspiration.