Green Roofing

A green roof, also known as a living roof, is a roof of a building that is partially or entirely covered with vegetation (grasses or sedum, typically). Green roofs serve many purposes for a building, for example to absorb rainwater, to insulate the rooftop, creating habitats for wildlife and lowering urban air temperatures. In cities particularly, green roofing is also called 'urban greening' and is a very popular trend at the moment.

A green roof can have several advantages, some of which are detailed below:

- Reducing heating (by adding mass and thermal resistance value)

- Reduce cooling (by evaporative cooling) loads on a building by 50-90%

- Reduce stormwater runoff

- Natural Habitat Creation

- Filter pollutants and carbon dioxide out of the air

- Filter pollutants and heavy metals out of rain water

- Help to insulate a building for sound

- Increase the lifespan of a roof drastically

- Increase real estate value

- Reduce energy usage

The main disadvantage of green roofs is the higher initial cost of the building structer, waterproofing systems and root barriers. There is also a degree of maintenance involved although the ongoing costs of most green roofs are relatively low.

Sources: here and here