When compared to conventional roofs, green roofs can enhance storm water management by
lowering runoff and enhancing water quality, save energy, reduce the urban heat island,
lengthen the life of roofing membranes, lessen noise and air pollution, sequester carbon,
increase urban biodiversity by creating habitat for wildlife, provide a more aesthetically
pleasing setting for living and working, and increase return on investment.
• Reduced amount of roofing materials in landfills
A typical conventional roof has a mechanical life expectancy of around 20 years. Old roofing materials for these roofs need to be removed, transported, and most likely disposed of at a landfill where they may not only take up space but also release pollutants. On the other hand, in terms of mechanical lifespan, green roofs are predicted to last 45 years or more. As modern green roofs are a relatively recent technique, the majority of this estimate is based on empirical data.
• Water quality of storm water runoff
Much has been written regarding the ability of green roofs to retain storm water. Depending on the type of green roof system, substrate composition and depth, roof slope, plant species, prior substrate moisture, and the intensity and length of the rainfall, the reduction in runoff typically ranges from 50% to 100%. For instance, green roofs on 20% of the buildings in Washington, DC may store about 958 million liters (253 million gallons) of rainwater annually. Water that is kept in the substrate will eventually evaporate or be lost through transpiration. Additionally, because it takes time for the substrate to become saturated and to drain, water that does runoff is delayed. Green roofs can assist prevent municipal drainage systems from overflowing and lessen possible erosion downstream since runoff is released over a longer period. Impervious surfaces harm rivers by gathering pollutants including oil, heavy metals, salts, pesticides, and animal excrement that wash into waterways, even in towns with separate storm water management systems. Green roofs lessen the likelihood of a CSO event by holding stormwater and lower the cost of storm water systems because they do not need to be as extensive. The quantity of roof runoff influences water quality downstream after it exits the roof. The effluent that runs off green roofs has an impact on the water quality, which is the opposite side of the issue. Numerous pollutants found in typical roofing materials already seep into runoff. And these contaminants will still be present in membranes on green roofs.
But do plants and growing surfaces have a beneficial or negative impact on runoff? Do they remove impurities or do they serve as a new source of toxins that worsen water quality? Contaminants of importance include heavy metals and nutrients. There is also a chance that debris removed from the air that was stuck to leaf surfaces will be rinsed off by rain and eventually seep into the stormwater system, changing the pollution from the air to the water.
At first glance, it appears that green roofs are a source of contaminants. studied the amount of metals and nutrients (Cd, Cr, Cu, Fe, K, Mn, Pb, Zn, NO3eN, NH4eN, Tot-N, PO4eP, and TotP) in runoff from extensive sedum-moss roofs and non-vegetated roofs, and found that green roofs were a source of pollutants, with the exception of N, which was retained by the vegetation. The overall N and P concentrations in runoff from two green roofs in North Carolina were also higher than those from the control roof and the actual rainfall from the green roof. The green roof also had the highest total P load compared runoff from asphalt, gravel ballasted, and extensive green roofs and reported that green roofs had the highest concentration of total solids with no significant differences for nitrate and phosphate concentrations, Nitrate and phosphate mean mass values from the green roof, however, were lower than those from the asphalt roof.
• Noise reduction
In addition to being bothersome, excessive noise can cause health issues like hearing loss, hypertension, ischemic heart disease, sleep disruption, and poor academic performance.High noise levels are frequently an issue in enclosed locations near tall buildings, along street canyons, and adjacent to industrial regions and airports in urban areas.
The potential to lessen sound pressure from roads and other sources in these places by introducing green roofs is intriguing because conventional roofs are often hard surfaces. Sound waves will be more effectively absorbed by vegetation and the growing substrate than they would be by a hard surface. The reduction in sound pressure on the side of the building away from the noise source or street canyon is correlated with the amount of roof space covered with vegetation. Sound waves enter the pore space and are reduced by the numerous interactions with the substrate particles since the growing substrates for green roofs often have a coarse texture.
Keep following us for more information about Roof planting; Roots is an Egyptian social marketing campaign run by Mass communication, Cairo University students, English section, Fourth level.
Our mission is to Create awareness about Roof planting & Green Roofs among the Egyptian society, build an emotional bond between Humans & Plants for the benefit of the planet, Take positive steps in their lifestyle.
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