terra, not terror

sharing ideas about a simpler way to live

Cool and conserve with a green roof October 3, 2007

Filed under: conserve, energy, environment, garden — terra @ 7:06 am

green roofGreen roofs could be the new trend in home and city cooling. By green, I mean literally covering roofs and walls with vegetation. Sturdy roofs could be home to moss, turf, and even trees. Walls covered in ivy also help, but the key to coolness is the roof.

Green roofs and walls can cool local temperatures by between 3.6°C and 11.3°C, depending on the city, suggests their new study. (32.6°F – 52.3°F)

Greenery absorbs less heat, and it also cools the air by evaporating water. Green plants also absorb sound, so the noise pollution of traffic in large cities could also be resolved.

Another benefit is less energy use because the natural cooling environment requires less air conditioning in the areas of the building that are covered with the green roof. This idea was tested in cities around the world, and researchers predict that in Riyadh, Saudi Arabia, for example, air conditioning use would go from 12 hours to 5 hours per day.

NASA cites a 2003 study on the effects of green roofs, which found them to drastically lower temperatures (by 50°F or more). They compared white surfaces to green, and found that white roofs still trap heat, and that green surfaces were much cooler. Green roofs also absorb more rainwater than regular roofs, thus reducing the workload of water treatment plants. They also found that green roofs leak less than regular roofs (I would like it if my roof didn’t leak!).

What about winter? Researchers in Canada have found some extra benefits of a green roof for winter energy savings as well. Buildings with green roofs saved 10% on energy used to heat the building. They protect heat from escaping, and reduce the impact of wind on the building.

Green roofs have plenty of environmental and financial benefits, and they look nice too!

(more photos)


3 Responses to “Cool and conserve with a green roof”

  1. Well it looks good and reduces our energy use! The back of our home is shaded by maple trees and cedars and in the last few years the foliage has gotten really full…the result has been a cooler home and less reliance on our air conditioner. This is a good bit of information to spread. As we look to our next home, the placement of plants, trees etc. is going to be an important point as I compare one home to another.

  2. terra Says:

    Sharon, That’s a great system too. I’ve read about using leafy trees to provide shade during the summer, and when the leaves fall off in winter, the sun shines through the branches to provide “passive solar heating.” (that’s fancy for – the sun can warm your home)

    I would really love to have a green roof. It sounds like the researchers from Penn State, quoted in the NASA study, are looking for ways to reduce the cost.

  3. gwen Says:

    My friend got to go on a tour of the new California Academy of Sciences builing in San Fran – it has a WICKED roof – not just green, also topographical.

    See here: http://www.calacademy.org/newacademy/

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