Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. Water is stored by the roof's substrate and then taken up by the plants, from which it is returned to the atmosphere through transpiration and evaporation. A study presented at the Green Roofs for Healthy Cities Conference in June 2004, cited by the EPA, found water runoff was reduced by over 75% during rainstorms. Green roofs play a significant role in retrofitting the Low Impact Development (LID) practices in urban areas. Green roofs can reduce stormwater runoff via water-wise gardening techniques. Water managementĪ green roof being used on a bike rack to keep bikes dry. Following this and other studies, it has now been estimated that if all the roofs in a major city were greened, urban temperatures could be reduced by as much as 7 ☌ (13 ☏). The Chicago City Hall green roof is one of the earliest and most well-known examples of green roofs in the United States it was planted as an experiment to determine the effects a green roof would have on the microclimate of the roof. In the case of Chicago, the city has passed codes offering incentives to builders who put green roofs on their buildings. Green roofs are a type of low impact development. Green roofs are becoming common in Chicago, as well as in Atlanta, Portland, and other United States cities, where their use is encouraged by regulations to combat the urban heat-island effect. On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 1.4–4.4 ☌ (2.5–7.9 ☏) cooler than they are on traditionally roofed buildings nearby. Traditional building materials soak up the sun's radiation and re-emit it as heat, making cities at least 4 ☌ (7.2 ☏) hotter than surrounding areas. Green roofs are also referred to as eco-roofs, oikosteges, vegetated roofs, living roofs, greenroofs and VCP H (Horizontal Vegetated Complex Partitions)Ī green roof reduces cooling (by evaporative cooling) loads on a building by fifty to ninety percent, especially if it is glassed-in so as to act as a terrarium and passive solar heat reservoir.Ī concentration of green roofs in an urban area can even reduce the city's average temperatures during the summer, combating the urban heat island effect. The term green roof may also be used to indicate roofs that use some form of green technology, such as a cool roof, a roof with solar thermal collectors or photovoltaic panels. There are two types of green roof: intensive roofs, which are thicker, with a minimum depth of 12.8 cm ( 5 1⁄ 16 in), and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are shallow, ranging in depth from 2 to 12.7 cm ( 13⁄ 16 to 5 in), lighter than intensive green roofs, and require minimal maintenance. They effectively use the natural functions of plants to filter water and treat air in urban and suburban landscapes. Green roofs are suitable for retrofit or redevelopment projects as well as new buildings and can be installed on small garages or larger industrial, commercial and municipal buildings. Green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, increasing benevolence, and decreasing stress of the people around the roof by providing a more aesthetically pleasing landscape, and helping to lower urban air temperatures and mitigate the heat island effect. Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof. Rooftop ponds are another form of green roofs which are used to treat greywater. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. It may also include additional layers such as a root barrier and drainage and irrigation systems. 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.
0 Comments
Leave a Reply. |