William R. Snodgrass Tennessee Tower
312 Rosa L. Parks Avenue, 2nd Floor
Nashville, TN 37243
For programs on this page call:
As leaders, our mission is to develop a sustainable culture throughout State Government. We will model this culture in TDEC and assist state agencies in implementing best practices that improve efficiency, reduce environmental impacts, and contribute to fiscally-sound government. Action-based approaches will focus on travel, building and purchasing.
The ancestry of green roofs began thousands of years ago. The most famous green roofs were the Hanging Gardens of Babylon which were considered as one of the Seven Wonders of the Ancient World, built around 500 B.C. They were built over arched stone beams and waterproofed with layers of reeds and thick tar. Plants and trees were then planted. In time, people used sod to cover their roof tops for the purpose of insulation, it kept their homes cool in summer and warm in winter.
The modern trend started when green roofs were developed in Germany in the 1960s, and has since spread to many countries. Today, it is estimated that about 10% of all German roofs have been “greened”. Green roofs are also becoming increasingly popular in the United States, although they are not as common as in Europe. A number of European Countries have very active associations promoting green roofs, including Germany, Switzerland, the Netherlands, Norway, Italy, Austria, Hungary, Sweden, the UK, and Greece. The City of Linz in Austria has been paying developers to install green roofs since 1983, and in Switzerland it has been a federal law since the late 1990s. In the UK, the uptake has been slow, but a number of cities have developed policies to encourage their use.
Many green roofs are installed to comply with local regulations, government fees, and often regarding storm water runoff management. In the areas with combined sewer-storm water systems, heavy storms can overload the wastewater system and cause it to flood, thus dumping raw sewage into local waterways. Green roofs reduce the total amount of runoff and slow the rate of runoff from the roof. It has been found that they may retain up to 75% of rainwater, gradually releasing it back into the atmosphere via condensation and transpiration, while retaining pollutants in their soil.
Washington, D.C. uses green roofs to filter and store some of its storm water on site, avoiding the need for expensive underground sand filters to meet D.C. Department of Health storm-water regulations. Combating the urban heat island effect is another reason for creating a green roof. Traditional building materials soak up the sun's radiation and re-emit it as heat, making cities at least 7 °F hotter than surrounding areas.
On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 2.5–8.0 °F cooler than they are on traditionally roofed buildings nearby. The Chicago City Hall green roof is one of the earliest and most well-known examples of green roofs in the United States; it was planted as an experiment to determine the effects a green roof would have on the microclimate of the roof. It has now been estimated that if all the roofs in a major city were greened, urban temperatures could be reduced by as much as 45 degrees Fahrenheit.
Examples of Tennessee’s green roofs can be found throughout the state. The Tennessee Tower, Music City Center, and Beale Street Landing are prime examples of utilizing this technology in an urban setting. Also included in the mix are several earthen shelter structures. The City of Athens, which houses Keep McMinn Beautiful, has a colfibrex building covered by vegetation as well as two Tennessee State Parks museums and interpretive centers, located at Fort Pillow State Park and Pinson Mounds State Park.
Installing a Green roof can be expensive, but they do not have to be. It could be as simple as letting your dog go green, with a small green roof for his doghouse. Many individuals are raising chickens for the fresh eggs, with a little more effort and money; the chicken coop could be green. The runoff from the green roof could be collected for the chickens, making the maintenance lower. It does not matter the size or the complexity of the green roof you choose, it is the fact that you are trying to do your part.