14 November 2018
Green Roofs: A Way to Sustain Environment
For many years, people were unaware about green roofs and it might be possible that even today some of them have never heard about it. Green roofs are the rooftops covered with vegetation partially or completely. They were introduced around 500 B.C in the famous Hanging Gardens of Babylon. The place was listed in Seven Wonders of the Ancient world and it had trees, grass, and shrubs resembling some magical garden. Furthermore, places like Scandinavia, Kurdistan and regions of Africa had also employed these roofs to protect their homes from cold, or heat. Their use has accelerated to the twentieth century due to deep ecological conscience, environmental groups’ pressure, and sustained research activity in the field.
Green roofs are one of the most effective ways of restoring environment and providing benefits to public, private, economic, and social sectors, as well as to global environment. These roofs encourage diversity of plants also knows as plant diversity in the area, and primarily people stay happier in a green and clean environment instead of a grey and unhygienic atmosphere. Also, these roofs stable the environmental imbalance by providing various advantages, such as prevention of heat island effect by decreasing the temperature which also results in less energy demands, curbing of greenhouse gases, and thermal comfort. Some of the other benefits include aesthetic advantages and restoring green areas to provide natural habitat for wildlife. Thus, employing the green roof strategy would improve the environment as well as provide certain benefits to people.
Growing urbanization and an increase in number of heat waves call for an alternative
which can lessen extremely high temperature. Green roofs are one of the best effective measures to prevent heat island effect as they cool the area by not reradiating the heat absorbed. Also, these roofs remove heat through evapotranspiration, a process by which water is transferred from the land to the atmosphere, which results in reduced temperature of root surface and the atmosphere. As compared to traditional roofs, green roofs reduce the temperature to a greater extent. In one experiment, these roofs decreased the temperature of surrounding by seventeen degrees Fahrenheit (Holladay 64). EPA (Environmental Protection Agency) claimed that “the surface temperature of a vegetated rooftop can be cooler than the air temperature surrounding it, whereas the surface of a traditional rooftop can be up to 90degrees F warmer.”(Happe para 17).
Moreover, the world is facing severe heat island effect because of which there has been a number of deaths, heat strokes, decreased quality of sleep, and decrease in labor productivity. Green roofs balance the environment by making it a safer place to reside. They adjust the microclimate by cooling and humidifying air. Some cities like Los Angeles constructed more than five hundred and sixteen thousand square meters of green roofs on five hundred and nine buildings, Toronto added two hundred sixty green roofs covering one hundred ninety-six thousand meters. As a result, these are protected from the severe effect of heat (Hoag 403).
Further, considerable increase of power consumption of air conditioning also requires some measure to reduce the cost of energy. Green roofs are energy efficient and the energy conservation lead to fewer greenhouse gas emissions. In one study, they decreased the daily energy demand by seventy five percent (Holladay 65). Additionally, they act as an insulator and result in reduced energy costs needed to provide cooling and heating. For instance, the energy used to remove additional heat gain in Florida was saved up to seven hundred watts and The Environment Institute found that green roofs save the air cooling energy approximately twenty six percent (Holladay 66).
The less heat fluctuation in twenty-four hour periods and reduction of temperature are advantages provided by green roofs. The amount of heat flux which enters the building is reduced due to their substrate layer. As a result, the inside temperature gets far more soothing and less humid. Experts proved through an experiment that heat fluctuation in green roofs was forty degrees less when compared to conventional roofs. In another study, green roofs reflected three to four degrees centigrade lower temperature inside building. (Dimitrijevic, et al S1518). Green roofs reduce the temperature thereby providing thermal comfort. The condition of mind is satisfied as the thermal environment is better. Due to reduced temperature inside the building people work with a satisfied mind resulting in better outputs. Also, the decreased outdoor temperature allows social groups to sit together and enjoy the nature. Experiment performed in Japan complied that green roofs reduce the building temperature between thirty to sixty degrees centigrade (Dimitrijevic, et al S1518).
Besides temperature issues, green roofs manage storm water by storing the water in their membrane or returning to atmosphere. The membrane of green roofs work as a sponge to remove pollutants as well as limit water discharge, thus, preventing soil erosion and effect of flooding (Happe para 11). An extensive research performed by EPA shows green roofs absorb 75 percent of rain events that are one-half inch or less and delay the run-off about forty-five minutes in a twelve hour periods (Holladay 65). They also control the storm sewer water by not letting it flow into the city sewers. According to the news article “Designing Green Roofs for Stormwater Management” written by Karen Liu “vegetation, growing medium, water retention layer, drainage, and root barriers possess the capacity of holding water.”
Moreover, our future generation might face difficulty of getting clean water as water pollution in today’s era is at peak. Fortunately, less water pollution and enhanced quality of water is linked to green roofs. The green roofs are made sloppy so that standing water does not damage the membrane and water is collected in drainage system for recycling purposes. During rain, the airborne particles such as heavy metals and pathogenic microorganism which flow through these roofs are collected by them resulting in better quality of water.
In today’s world, growing industrialization impacts the city’s atmosphere to the greater extent. Extensive planting is required to enhance the air quality, unfortunately, the goal of development is met by deforestation. Green roofs contribute to reduction of number of harmful gases (carbon monoxide, nitrogen dioxide, ozone) and pollutants through deposition in themselves. Photosynthesis in plants results in carbon dioxide consumption and release of oxygen in the atmosphere. They also help to remove airborne particles and volatile organic compounds from the air.
Due to bad air quality, a number of respiratory diseases impact people’s health. For instance, a large number of deaths are reported every year at the hospital where my grandfather,
Dr. Kuldip Singh, worked. He explained in an interview that poor air quality causes many people to die from asthma, respiratory tract infections, obstructive lung disease, and other lungs diseases
(Singh). Green roofs address this issue directly or indirectly by providing a better quality of air.
Thus, there can be a reduction of the risk of death and harmful diseases with green roofs.
In many places, green areas have been replaced by tall buildings and the natural habitat of wildlife has been exploited. Humans have destroyed the greenery for their own benefits and might regret in the near future. Thus, green roofs can play a major role in restoring the green environment and also giving back the wildlife their natural habitat. Pollinators such as insects, bees, butterflies, and birds can be attracted to them.
Despite of various advantages that green roofs provide these have been still criticized due to cost effectiveness, lower temperature, and beneficial only to upper levels of buildings. Cost effectiveness is one of the major argument that is held against green roofs. Experts suggest that green roofs lack design standards which leads to increased prices. Thereafter, it is also highlighted that green roofs are not cost effective on private basis (Blackhurst, Michael, et al 138). The material required to build a green roof is more than the material used for traditional roofs. In one study, 1900 multifamily green roof conversion costed around 1440 dollars per household whereas attic floors costed 340 dollars per household (Blackhurst, Michael, et al 140).
In contrast, an expert proved that green roofs cost only ten percent higher than traditional roofs and provide a number of benefits which letter ones do not (Holladay 64). Sometimes, homebuyers are misguided by some experts who show them the high-priced estimates of green roofs’ installation. By comparison, the asphalt and shingle used in traditional roofs cannot outweigh the benefits provided by green plants.
Further, green roofs are opposed by some people because they provide benefits only to the upper levels. Only tall buildings such as commercial workplaces enjoy the benefits of green roofs. Opponents argue that green roofs are not beneficial at street levels; instead, plants and grasses should be planted to get full benefits (Hoag 403). In a modelling study based on the European heatwave, planting twenty-five percent of roofs, it was found that green roofs do not benefit at the street level because the wind prevented cooler air from reaching the ground level
(Hoag 404). Also, experts criticize the fact that green roofs are one hundred percent advantageous to a few top floors of buildings. They are not worth it for single story houses because those are deprived of thermal comfort and insulation in summer and winter respectively.
Undoubtedly, plants and grasses benefit the environment, but in today’s growing world, green roofs are needed to address various issues, such as drainage of standing water, reduced temperatures inside the buildings, and fulfilment of natural green spaces. Planting on land is not possible in big cities like New York, Los Angeles, and many other metropolitan cities around the world.
Above all, some experts suggest that green roofs do not lower the temperature significantly as they reradiate the heat stored during the night. In Chicago, dark roofs were replaced by green roofs to see if there was any benefit, but the latter did not alter the temperature significantly (Hoag 403). During a heatwave in Washington, ninety percent of area covered with green roofs lowered the temperature by .5 degree centigrade which is not a significant decrease (Hoag 403).
Although, the area of green roof covered with plants and the reduction of temperature are correlated, various other factors are taken into account when people expect more benefits. When fully covered with plants, the conducting research revealed that surface temperature of building is reduced up to sixty degrees centigrade (Dimitrijevic, et al S1518).
Human beings have done a lot of deforestation in order to construct tall buildings or to bring advancement in the world. If the action is not taken now it would be too late and our future generation might face a lot of difficulties. The kinds of actions, such as homeowners planting green roofs, can be buffered if people understand the value of green roofs and take initiatives to make the concept successful. According to a 2016 article in National Geographic online magazine, a law was passed in San Francisco mandating that new construction use between fifteen to thirty percent of roof space for green roofing or solar (Snow para 2). However, these kinds of actions can only be effective if people are not misguided by the negative views of opponents on the value of green roofs. Accurate information on the costs and benefits of green roofs will create buy-in so more people will actively employ green roofs. As a result, not only the environment will get better but also people will be comfortable at their homes, workplaces and outside environment.
Overall, green roofs provide certain benefits which outweigh the problems that critics say are associated with them. Humans and all life on earth depend on a healthy environment to survive, but Mother Earth needs help from humans to enable that survival, and a cleaner and greener environment. Thus, green roofs should be employed as they play a major role in protecting the environment and benefiting people and all other things that breathe. ?
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Liu, Karen, and Xeroflor, Bonar. “Designing Green Roofs for Stormwater Management: Technological Advances Offer Low-Weight Options. Green Roofs, 2018, http://www.greenroofs.com/content/articles/153-Designing-Green-Roofs-for-StormwaterManagement.htm#.W1iQotJKgdU. Accessed 24 July 2018.
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