Why Do Green Roofs Have Alternating Media Depth

Fine sands 0 05mm 0 25mm do little to improve the physical properties of a growing media and may result in reduced drainage and aeration.

Why do green roofs have alternating media depth.

Sand a basic component of soil ranges in particle size from 0 05mm to 2 0mm in diameter. However research and innovation continues to expand the possibilities and benefits of urban greening with green roofs. Green roof technology is still under development in the united states. Their roofs are essentially green roofs and usually deep intensive roofs that need considerably more structural support than the more shallow extensive type.

Green roofs are designated as extensive semi intensive or intensive. Green roofs also have a fairly stable surface temperature remaining at air temperature or cooler while traditional rooftops can soar up to 90º f 32º c above air temperature source. The designation depends on their depth type of vegetative cover and function. Gravel to protect built up roofs.

Container gardens on roofs where plants are maintained in pots are not generally considered to be true green roofs although. When the depth of water stored in the green roof growing media was treated as a variable roof storage was varied from 0 25 to 3 0 inches of storage using the 28 years of state college s daily rainfall data the results see figure 3 showed that the 3 5 inch green roof with 1 6 inches of water storage with a drainage layer and plants was an excellent choice. Green roofs are usually covered with an artificial soil or growing medium to minimise roof loads but earth sheltered homes often use heavier natural soil as a continuation of the indigenous site conditions. The origin of the term is often ascribed to such rooms historically being painted green.

Here alternating layers of roofing felt usually fiberglass and hot applied asphalt are combined to create a long lasting roof system. A built up roof bur sometimes called a tar and gravel roof is a tried and true style of flat roof. Green roofs are differentiated by the depth of the growing medium as this directly relates to weight the primary structural concern. The planting medium in extensive green roofs ranges from 1 6 to 6 inches deep and while deeper systems have been installed they are not favored as much as the shallower systems drought tolerant sedums succulent plants and grasses are the typical plants used since they are shallow rooted and use little water plant diversity on these roofs is kept low to simplify care and to be sure all plants.

Intensive roofs are those greater than 4 inches in thickness with some as deep as 2 feet or more making a wide variety of plants including bushes and even small trees possible. Because green roofs protect the roof membrane from harsh weather and ultraviolet uv radiation they can last twice as long traditional roofs.