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Name: Claudia L.
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: July 2004


Question:
Hello, Can you please tell me if their would be a benefit to the environment by planting trees on skyscrapers or using reflective surfaces as roof tops on those same buildings?



Replies:
Yes, there would be a benefit if either of your suggestions were adopted.

Planting trees would shield the building from the direct rays of the sun (especially if the building is not very tall). Further, due to the water emitted by the trees which is evaporated, especially on warm days, the top of the building would be further cooled. One could, of course, put water tanks on the roof; the evaporation of the water would cool the building without the trees being needed.

Reflective surfaces could work well also. The sunlight could be returned to space without heating the building or, in fact, any part of the earth. Further, if the light is reflected specularly -- without change of wavelength -- there would not be a greenhouse effect. The greenhouse effect works if sunlight is incident on the earth and warms the earth, which then radiates the heat energy at a longer wavelength (characteristic of the temperature of the earth and not of the sun). The longer wavelength electromagnetic radiation is efficiently trapped by the atmosphere, especially if it contains significant amounts of carbon dioxide and other "greenhouse" gases.

Best, Dick Plano, Professor of Physics emeritus, Rutgers University...


I do not see any harm provided the roof is strong enough to support the plants and their soil. Dirt is pretty heavy.

Vince Calder



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