Why Are Green Roofs Environmentally Responsible?

  January 12, 2012

Today's tip is the reasons why green roofs are an environmentally responsible choice. That's certainly a common-sense notion, but let's take a look at why.

First, a bit of definition: There are two varieties of green roofs: intensive and extensive.

Intensive green roofs are the fancy kind, most often recognized as roof gardens that allow people to walk around and relax. They often include flowers, bushes, and even small trees. Extensive green roofs are usually less involved, with a thinner planting medium, and usually include smaller plants with shallower roots, like grass and flowers. They have a saturated weight of 12 to 50 pounds per square foot.

Green roofs can save a building energy because the added insulation they provide do not allow heat from the sun to penetrate the building. A study by National Research Council of Canada found that green roofs reduced demand for air condition by 75 percent. Green roofs also help reduce the urban heat island effect because they absorb energy that would otherwise be reflected back to the atmosphere, cooking cities more so than their outlying suburbs.

Green roofs also help prevent stormwater from overtaxing storm drains by absorbing rainwater. According to Green Roofs, Healthy Cities — an organization promoting the benefits of green roofs — depending on the type of plants and thickness of the growing medium, green roofs retain 70 to 90 percent of the precipitation that falls on them in the summer and 25 to 40 percent in the winter.

Finally, green roofs improve air quality because plants filter noxious chemicals and can capture and absorb airborne pollutants.


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