Conventional Roofing and the Secret Life of Green Roofs - Term Paper Example

Green Roofs vs Conventional Roofs Introduction Green roofs are the roofs with vegetated surfaces. Green roofs have been used for a long time in history particularly in the domestic houses. Generally, conventional roofs have been used more than the green roofs in buildings in the urban areas. As the concerns about the environmental effects of buildings increased during the late 20th century, green roofs became legally required in many countries around the world. “The city of Portland, Ore., is aiming for 49 total acres of eco-roofs in the city by 2013” (grist.org, 2012). On the other hand, conventional roofs are the more common type of roofs made of such materials as glass, wood, concrete, and bricks. This paper draws a comparison between the green roofs and the conventional roofs. Types The conventional roof has many types. Types of the conventional roof include but are not limited to the single ply roofs, built-up roofs, metal roofs, and asphalt shingle roofs. Single ply roofs are sheet-like membranes manufactured in the factory. Thermoplastic membranes and thermoset membranes are the two types of single ply membranes. Built-up roofs contain several layers of reinforced membranes and modified bitumen roofs. Built-up roofs are the most common as well as the oldest type of conventional roofs. They are also called as the gravel or tar roofs. There are three components in the built-up roofs, which include a layer of waterproofing, a reinforcement layer, topped with a surfacing layer. It is installed with the help of asphalt or coal tar. Structural metal panel roofs are used for roofs with low slopes as they have the characteristic quality of water barrier. They can also be used for roof assemblies with steep roofs. The structural metal panel roofs are constructed in such a way that water cannot pass through the joints. These roofs are installed in a broad range of substrates. Asphalt shingle roofs are amongst the most commonly used roofs where the slope is steep. There are two types of asphalt shingle roofs; organic roofs and fiber glass roofs. “Organic consists of paper saturated with asphalt to make it waterproof with a top coat of adhesive with embedded ceramic granule” (gogreenconstructionnow.com, n.d.). Owing to their greater weight, organic shingle roofs offer better blow-off resistance as compared to the fiber glass roofs. Roof shingles may contain single or multiple layers, but all types contain an adhesive strip which is sun-activated and serves as a sealant for the rows. There are three main types of green roofs; extensive green roofs, semi-intensive green roofs, and intensive green roofs. The extensive green roofs are used in ecological landscapes. The type of vegetation used in the extensive green roofs ranges from moss and herbs to grasses. The depth of substrate in the extensive green roofs is between 60 mm and 200 mm, and their weight is in the range of 60 kg/m2 to 150 kg/m2 (Livingroofs.org, 2012). The cost of extensive green roofs is the lowest of the three types of green roofs. The semi-intensive green roofs are used in ecological landscapes as well as gardens. The type of vegetation employed in them includes herbs, grass, and shrubs. Their depth of substrate ranges from 120 mm to 250 mm whereas their weight is generally between 120 kg/m2 and 200 kg/m2. The cost of semi-intensive green roofs is periodic. The intensive green roofs are used in parks and gardens. The type of vegetation used in the intensive green roofs ranges from perennials and shrubs to trees. Their depth of substrate is generally 150 mm to 400 mm. The weight of the intensive green roofs is between 180 kg/mm2 and 500 kg/mm2. The cost of intensive green roofs is the highest of the three types of green roofs. Cost Payne et al. (n.d.) conducted a research to compare the expenses associated with the green roofs to the cost of conventional tar roofs to identify the places where the installation of a green roof is more feasible economically than the conventional roof. As a result of their research, Payne et al. (n.d.) found that the initial cost of the green roofs takes anything between 300 and 400 years to payback. Payne et al. (n.d.) found that the period of payback of the initial cost of green roof is shorter in the warmer climates as compared to the colder climates. “This is mainly because in the winter the insulation for a green roof has a greater R‐value but because the solar reflectance is greater then an asphalt roof the rooms below are not warmed by the sun, thus requiring more energy spent for heat” (Payne et al., n.d.). The cold climate of the New York City makes the payback period the longest of the four cities included in the study; Houston, New York City, Miami, and Los Angeles. From their research, it can be concluded that green roofs are best-suited to the places with warmer climates because of the shorter payback period whereas the economic feasibility of the conventional roofs is more than the green roofs in the places with colder climates. Benefits Green roofs offer a lot of advantages including economic savings and environmental benefits. Installation of green roofs cuts down the heating and cooling costs. “The layer of vegetation acts as an insulator which absorbs the heat from the sun to keep the building cooler in the summer and warmer in the winter” (Payne et al., n.d.). Green roofs do not require roof repairs that the conventional roofs require periodically. Green roofs increase the amount of green space in the area that bring the carbon emissions down. “Research in London since 2002 has also shown that some green roofs in London are providing refuge for a number of nationally rare and scarce species” (sustainable-eastside.net, 2004, p. 15). On the other hand, the conventional roofs are sometimes much cheaper as compared to the green roofs. For instance, fiber glass is quite cheap and does not incur much maintenance or repair cost as well. Conventional roofs are easier to construct, and can be immediately laid. In many cases, conventional roofs are prefabricated members prepared in the factory and are just brought and installed at the required location. In this way, conventional roofs facilitate speedy construction. In addition to that, conventional roofs provide room for construction above them whereas construction of another storey atop the green roof is very difficult. Life Expectancy Life of the conventional roofs is generally longer as compared to the green roofs. Life of any kind of roof typically depends upon how it has been maintained. Most of the green roofs require a lot of maintenance. “Green roofs can be designed to be relatively low maintenance, especially after the establishment period, but with rare exceptions ignoring maintenance or giving it short shrift is inviting problems” (themindfulword.org, 2012). Maintenance works of the green roofs include but are not limited to cutting and shaping the plants, regularly watering them, and profiling the sand so that it does not come off the beams. On the other hand, conventional roofs can sustain for several decades without much maintenance. For example, service life of the built-up roofs is generally between 15 and 25 years (gogreenconstructionnow.com, n.d.). The reinforced concrete (RCC) roofs can sustain up to five decades or more with minimal maintenance. Conclusion There is a wider range of types of conventional roofs as compared to the green roofs. Green roofs are environment-friendlier as compared to the conventional roofs. Life expectancy of the conventional roofs is greater than the green roofs. Green roofs require much more maintenance than the conventional roofs. References: gogreenconstructionnow.com. (n.d.). Conventional Roofing. Retrieved from http://www.gogreenconstructionnow.com/?page_id=89. Grist.org. (2012). The secret life of green roofs. Retrieved from http://grist.org/article/2010-04-02-the-secret-life-of-green-roofs/full/. Livingroofs.org. (2012). Introduction to Types of Green Roof. Retrieved from http://livingroofs.org/2010022858/green-roof-types/greenrooftypes.html. Payne, D., Christner, M., Turner, Q., Sapochetti, G., and Savilonis, B. (n.d.). The Cost of Green Roofs vs. Conventional Tar Roofs. Retrieved from http://m.wpi.edu/Images/CMS/UGP/quantay-turney-2-poster_for_AFC.pptx.pdf. sustainable-eastside.net. (2004, Mar.). Green Roofs Benefits and Cost Implications. Retrieved from http://www.sustainable-eastside.net/Green%20Roofs%20Report%202.07.05.pdf. themindfulword.org. (2012, July 19). Green Roof Maintenance: How to extend the life of your green roof. Retrieved from http://www.themindfulword.org/2012/green-roof-maintenance/. Read More