A vegetated roof, or green roof, is a layered system installed on top of a roof that includes vegetation growing in a lightweight soil medium. It provides environmental benefits like decreased stormwater runoff and reduced energy usage. There are two types - extensive roofs have shallow soil depths under 6 inches while intensive roofs have deeper soil and support a greater variety of plants but require more maintenance. Initial installation costs of vegetated roofs are higher than traditional roofs but they provide long-term savings and last longer through better insulation and protection from temperature fluctuations.