Green roof

Green roof

A green roof is a roof of a building which is partially or completely covered with plants. It may be a tended roof garden[?] or a more self-maintaining ecology like a living wall[?] or breathing wall[?]. An earth structure[?] often has such a roof, as plants simply grow naturally over it, making a hill that is from some angles indistinguishable from a natural one.

Green roofs are used to:

Provide amenity space[?] for building users - in effect replacing a yard or patio[?]
Reduce heating[?] (by adding mass and thermal resistance value[?]) and cooling[?] (by evaporative cooling) loads on a building - especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir[?]
Reduce the urban heat island effect
Increase roof life span[?]
Reduce storm water run off - see water-wise gardening
Filter pollutants and CO2 out of the air - see breathing wall[?]
Provide locally grown food[?] - in which case it is known as a roof garden[?]
Increase wildlife habitat[?] in built up areas - see urban wilderness[?]

A green roof is often a key component of an autonomous building.

According to Green Roofs for Healthy Cities (a network of public and private interests founded by Steven W. Peck[?] based in Toronto):

"In North America, the benefits of green roof technologies are poorly understood and the market remains immature, despite the efforts of several industry leaders. In Europe however, these technologies have become very well established"