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.