Nrca roofing manual 2013 pdf


Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof. 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. They effectively utilize the natural functions of plants to filter water and treat air in nrca roofing manual 2013 pdf and suburban landscapes.

There are two types of green roof: intensive roofs, which are thicker, with a minimum depth of 12. Green roofs improve and reduce energy consumption. A modeling study found that adding green roofs to 50 percent of the available surfaces in downtown Toronto would cool the entire city by 0. On Chicago’s City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 1.

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. In the case of Chicago, the city has passed codes offering incentives to builders who put green roofs on their buildings. 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 degrees Celsius. 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. Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. Often, phosphorus and nitrogen are in this category of environmentally harmful substances even though they are stimulating to the growth of plant life and agriculture.

When these substances are added to a system, it can create mass biological activity since they are considered limiting factors of plant growth and by adding more of them to a system, it allows for more plant growth. Elevation 314, a new development in Washington, D. Department of Health storm-water regulations. Even in high-rise urban settings as tall as 19 stories, it has been found that green roofs can attract beneficial insects, birds, bees and butterflies. They can also filter pollutants and heavy metals out of rainwater. An additional environmental benefit of greens roofs is the ability to sequester carbon. Carbon is the main component of plant matter and is naturally absorbed by plant tissue.

The carbon is stored in the plant tissue and the soil substrate through plant litter and root exudates. Variations occurred among the different species of plant used. The sequestration can be improved by changing plant species, increasing substrate depth, substrate composition, and management practices. Also, by increasing the substrate depth would allow for more area of carbon storage and diversify the types of plants with greater potential of carbon storage. The direct carbon sequestration techniques and methods can be measured and accounted for.