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The concept of green roofs is basically about growing plants on roofs, thus helping to replace the green footprint that had been destroyed due to the construction of the building. Green roofs are the most prevalent in Germany, which is a country that is widely regarded as the leader in the research of the green roof concept, both the usage as well as the technology. According to estimations, it is thought that around 10 percent of the flat roofs in Germany are green. The green roofs that are used these days can be classified as ‘extensive’ or ‘intensive’ systems, according to the usage of the roof and the plants used. Extensive green roofs use mosses, grasses, herbs, and succulents like Sedum, which are tolerant to droughts, which do not need much maintenance, can be grown in a layer of substrate that can be as shallow as 1.5 inches (2.0 cm), and generally are inaccessible to the public. In contrast, a wide range of species of plants are grown on intensive green roofs, such as shrubs and even trees, which require substrate layers that are deeper, are usually grown on flat roofs, need intensive maintenance, and are usually areas that resemble parks which are accessible to people.
How are Green Roofs Beneficial? There are several benefits of adopting green roof technologies. Apart from the obvious psychological and aesthetic benefits of garden-like environments surrounding you, some of the common economic and ecological benefits are: a reduction in the consumption of energy; air and water purification; an improvement in the management of stormwaters; recovering green spaces; and the mitigation of the heat island effect in urban areas. Due to impervious surfaces being prevalent in urban areas, many people feel that the primary benefit of green roof technology is the reduction in the stormwater runoff. The rapid and large amounts of stormwater runoff from the surfaces of roofs often cause flooding, and increase in the erosion, and can even lead to raw sewage being directly discharged into rivers. And, the large amounts of stormwater runoffs also mean that larger quantities of water have to be treated before it becomes suitable for drinking. One of the main benefits of green roofs is the ability they have of absorbing the stormwater and then releasing it gradually over several hours. It has been shown that green roofs have the ability of retaining 60 to 100 percent of the stormwater that falls on them. Plus, green roofs are longer lasting compared to ordinary roofs since they are protected from factors like extreme temperature fluctuations and ultraviolet rays which cause roof surfaces to deteriorate. Green Roof Research The green roof research that is currently ongoing is focused on evaluating the species of plants that are suitable to be grown on roofs, the methods of propagation as well as establishment, nutrient and water requirement, substrates, and the quantity and quality of water runoff. The evaluation criteria of plant species are: at what rate they can be established; their capacity to withstand invasive weeds; tolerance of cold and heat; resistance to fire; tolerance of drought conditions; capacity of persistence and survival. A number of experiments are being conducted on roof platform simulations at various research centers.