A green roof system consists of plantings and/or landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof is made up of a waterproofing system and it's associated components, a drainage layer, thermal insulation and an aeration layer, and an overburden of growth medium and plantings. Green roofing systems are divided into three primary categories: extensive (shallow), semi-intensive (moderate depth) and intensive (deep).
There are many benefits for choosing a green roofing system. Green roofs reduce the urban heat island effects, provide storm water run-off management, add valuable space providing economic benefits, add to air and water purification, in addition to being energy efficient year-round.