This document discusses green roofs, which are engineered lightweight roofing systems that support plant life installed on top of structures. Green roofs provide benefits like reducing stormwater runoff, mitigating the urban heat island effect, and improving air quality. There are two main types - intensive green roofs which are like roof top gardens with thick growth media and vegetation but higher costs, and extensive green roofs which are thinner and lighter like sod roofs and have lower costs and maintenance needs. Installing a successful green roof requires a team approach involving various professionals.