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Green Roof Vs. Cool Roof

Many cities have created goals to reduce their carbon footprint over the next couple of years. One way they have found to do this is through the roofs of buildings, i.e. "green" and "cool" roofs.

You might be wondering just what green roofs are, they refer to roofs that are covered either completely or partially with living plants. They have many benefits including protecting the roof from sunlight, reducing storm water runoff and pollution, reducing green house gas emissions, improving air quality and keeping buildings cooler, as plants absorb the majority of the sun's energy. Green roofs contain a waterproof membrane, a drainage system, a thin layer of soil and, of course, plants. These types of roofs can be installed almost anywhere, including residential, commercial, educational and government buildings.

Green Roofs Report by NRDC found that green roofs in New York City were 60 degrees Fahrenheit cooler than regular black roofs. Furthermore, the report also explains that "green" roofs are either "extensive" or "intensive." "Extensive" roofs have hardy, drought-tolerant plants that do not need fertilizers or pesticides and "intensive" green roofs mimic a park-like setting where there is no limit as to what plants or trees are installed. Of course there is more money and planning that goes into the "intensive" type roofs, but both provide the same benefits. In June 2007, it was determined that 6.6 million square feet of roofs have been either converted or were in the process of being converted into "green" roofs in the United States.

"Cool" roofs are made of materials that help reflect the sun's energy, such as light-colored paints, roof tiles, coatings and shingles. They can be installed on all types of roofs including, flat or sloped roofs, commercial or residential buildings and new or old structures. They are able to keep roofs between 50 to 60 degrees Fahrenheit cooler than traditional roofs and can help reduce energy use and green house gas emissions as well. They do not, however, reduce storm water runoff, help with water pollution or sequester carbon, and may cause buildings to require more heat during the winter months. "Green" roofs will actually help insulate buildings during the cold season. In order for buildings to become more environmentally friendly, "cool" roof systems can have additional structures to help capture storm water runoff, as well as help with insulation. "Green" roofs may have many more benefits, but "cool" roofs are still a better choice than traditional roofs.

"Green" roofs do not have to be expensive. Urban Design Tools: Low Impact Development states that the average cost for a "green" roof in the U.S. is "between $15 to $20 per square foot for all use types, i.e., high density, residential, commercial, industrial, etc." In other countries, such as Germany, these costs range from $8 to $15 per square foot because "green" roofs are more common and a whole service industry was developed in order to install them. Perhaps as "green" roofs become more common, they will also become cheaper in the U.S.

Once the roof is created, very little maintenance is required. Plants may require some watering until they are fully developed. "Extensive" types sometimes contain a permanent drip tubing system so that water can run directly into the roots of the plants, taking care of those that may require regular watering. In order to decrease maintenance and survival of the plants, they should be selected based off of what type of environment they can withstand.

"Cool" roofs are even cheaper than green roofs, only costing $0.75 to $1.50 per square foot and a single-ply cool roof membrane usually ranges from $1.50 to $3 per square foot, according to EPA.Gov. It also claims that "cool" roofs can save $0.50 per square foot annually, while still taking into consideration the possibility of increased heating costs in the winter. Federal Tax Credits for Energy Star qualified that roofs and reflective asphalt shingles may also be given, allowing for additional tax savings.

In order to reduce the "urban heat island effect," people are considering creative ways to turn their heat-absorbing roofs into landscapes or reflective devices. Creating a "green" or "cool" roof can help you save money and reduce your impact on the earth. They are becoming more and more common and are not very expensive. If you feel like a "green" or "cool" roof is too much work or money, perhaps you can start small by just turning your garage or shed into an eco-friendly roof. Any little bit helps and you might find it was not as hard or expensive as you thought.

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Stephanie Siemek is a freelance writer whose work can be found on

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