Green roofs or living roofs have a number of advantages over conventional roofs. In addition to being beautiful, green roofs reduce runoff problems, provide habitat for wildlife, buffer noise, filter the air and reduce the ‘heat island effect’ in cities. They also improve the energy efficiency of buildings, reducing heating and cooling costs.

All these benefits and more have made green roofs popular across Europe, especially in Germany, Austria, Switzerland and France, where experience has shown a proven return on investment.

One drawback, however, is the added costs of green roof materials and reinforcing the structure to carry the extra load. This was foremost in my mind when I built the dome for Mother Earth News magazine. (See post on January 22, 2009 below.) My goal was to make the green roof as ‘green’ as possible.

The design I arrived at minimizes synthetic, non green materials typically used on green roofs – insulation, root barriers, filter fabric, drains and rubber waterproof membranes (EPDM, etc.). It also avoided added structural reinforcement because domes are inherently stronger than other forms. While not perfect, my design is a step in the right direction, and it’s very simple. The earthbag dome was draped with two layers of 6 mil plastic as a moisture barrier. Shade cloth was placed over this on the steep upper half to prevent erosion. Backfill was built up in layers and tamped (road base first and then topsoil), and then planted with drought-resistant grass. It has weathered one monsoon season with no leaks, mold or other problems.

If you haven’t voted for your favorite green roof at Huffington Post, I believe there’s still time. When you vote, think about which design is the greenest.


Comments

Green Roofs — 3 Comments

  1. I agree. Designing an appropriate green roof takes a bit of research. In fact, for a long time I didn’t use them because of all the associated problems such as toxic materials and water use. I’m more interested now that I’ve found some better solutions such as lightweight, modular trays that can be removed.

  2. Green roofs are indeed a good solution, not only for technical reasons but also because they add a very pleasant element to the building. It is not completely clear yet if they are useful in every kind of climate location. I remember a particular green roof I saw in Portugal that needed sprinklers working most of the summer period because the temperatures were too high. I know there are different solutions, all with different maintenance levels, the problem is that some of the architects designing green roofs don’t know that and end up specifying green roofs just because they look nice and sometimes choose the inappropriate solution for that location.

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