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Kimberly Powell


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If green roofs were mandatory in cities would there be less development and building?

William McDonough knows the benefits that come from designing and implementing green roofs. McDonough has helped design living roofs for big companies such as Nike and Ford Motors. But many companies and homeowners overlook the benefits of green roofs. One benefit of green roofs is that they keep the internal temperature of a building steady throughout the year. The National Research Council of Canada found that having a green roof reduced the daily energy demand for air conditioning in the summer by 75%. Toronto is the first North American city to pass a law mandating green rooftops for all new residential, commercial and industrial developments. Any new construction with floor space of more than 2,000 square meters must devote between 20 and 60 percent of its roof to vegetation. But with green roofs comes an unwanted financial upfront cost. Will developers decide that the benefits outweigh the costs for installing green roofs?

If green roofs were mandatory in cities would there be less development and building?


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    May 22 2012: http://www.dailymail.co.uk/sciencetech/article-1031438/Pictured-The-floating-cities-day-house-climate-change-refugees.html "Lilypad Cities"

    I direct you all to that link to show how human ingenuity is illimitable. This is not to say that it provides the best, or even good solutions, but green roofs will not hinder architectural designs. We are too creative, and our subjects (plants) are too intelligent and tenuous for that.

    With the idea of "green roofs" we tend to think of roofs that are populated by things that are uniformly green, that is, the types of leafy lollipop spheres that represent a green space on a designer's computer screen. To me, the most exciting thing about green roofs is the potential for intense variation across buildings, across countries--reflecting the particular nuances of the landscape. Is it too warm for cherry trees in Miami? Plant a Japanese garden of mangroves and saw palmetto. Is it too cold for cherry trees in Maine? Plant a forest of white spruces. They are used to shallow, moist soils.

    From the plant's point of view, the greatest problem will be a lack of soil consistent with the constraints of a rooftop. Bonsai trees are bonsai trees simply because they are maintained and pruned in a pot. To avoid this, we can a) start adapting green roofs to the climate b) make roof-building a whole new discipline, in which they become new earths, not merely shelters for those living or working below them.

    Another thing that we must not overlook, however, is that if we start explicitly designing buildings to house incredible rooftop gardens, we may start building bigger roofs, and bigger buildings. That's a long way off though!
    • May 24 2012: That is such an inspiring article! It is sad, however, to see everything we could accomplish in the way of being sustainable that we haven't. Regarding trees on green roofs, I think that food crops would be a better choice than trees per se. It would be a way to make cities less reliant on the commercial farm and transportation systems that provide almost all of our food, so that if ever either of those systems failed, we would have a fallback. Growing crops would also lessen the problem of not having enough soil depth, because the plants' roots would not grow as long as tree roots.

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