Green Roof Definition Epa

Green roof runoff does contain concentrations of some nutrients and other parameters but values are in line with other planted systems.

Green roof definition epa.

A green roof is a vegetative layer grown on a rooftop. Green roofs are covered with growing media and vegetation that enable rainfall infiltration and evapotranspiration of stored water. The green roof at the epa regional office is an extensive modular design meaning that the plants are growing in 2 x 4 trays made of recycled plastic. They are particularly cost effective in dense urban areas where land values are high and on large industrial or office buildings where stormwater management costs are likely to be high.

A green roof or rooftop garden is a vegetative layer grown on a rooftop. Green roofs can significantly reduce the amount of rain water that would otherwise run off an impervious roof surface. A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems.

Green roofs have a layer of plant material that absorbs water like a sponge. They capture water when it rains slowly releasing it through evaporation and plant use. Green roofs provide shade remove heat from the air and reduce temperatures of the roof surface and surrounding air. These two mechanisms reduce temperatures of the roof surface and the surrounding air.

As with trees and vegetation elsewhere vegetation on a green roof shades surfaces and removes heat from the air through evapotranspiration. These trays cover 20 000 square feet or almost 60 of the 35 000 square foot total roof surface above the 8th 9th and 10thfloors of region 8 epa headquarters. It may also include additional layers such as a root barrier and drainage and irrigation systems. Due to the volume reduction actual nutrient loadings from green roofs are less than asphalt roofing runoff or otherwise manageable at the downspout.