Irrigation needs are stronger in the Southwest and California. In general, roof plants have to be tougher than those growing in the ground it can be hot, dry, and windy up there, and weed seeds carried by wind and birds can still invade. Plant choices for green roofs, of course, depend on local conditions. After six years, measurable results are in: The roof plantings retained 77 percent of rainfall that fell during the first data-collecting period, and temperatures have been as much as an astounding 59 degrees lower than conventional black roofs on neighboring buildings.Ī playhouse in North London.

One has low plants (primarily sedums) making use of minimum soil depth the other includes a mix of sedums with taller, drought-resistant grasses and perennials requiring a deeper soil base. The residential-size, 3,000-square-foot display includes two elevated waves. The 3,300-square-foot roof of the house they call Wings of Earth uses nine species of sedum with accents of butterfly-attracting, perennial dianthus and phlox - all visible from the upper floors of the home.Īs a model for green roof design, the American Society of Landscape Architects commissioned Michael Van Valkenburgh Associates to create a rootop research garden atop its Washington, D.C., headquarters. In Sonoma County, California, Kevin Falkerson and Kerrie Lee Cole, the design-and-build team at Symbios, create one-of-a-kind “artisan” roofs that display a surprising diversity of plants. (Photo by: Barbara Ries)Īnother approach designers take is to mix up the plant palette on roofs. Currently he’s at work on a similar system suited for subtropical climates.Ī green roof atop a house in Mill Valley, California, by McGlashan Architecture. For those who desire a similar look, Hellwig has developed an easy-to-install mat containing a pre-cultivated epiphytic ecosystem that can adhere to most any roof or wall. Thus the lightweight living roof requires minimal maintenance and looks as connected with the earth as the Hobbits’ homes in The Lord of the Rings. Turning away from typical earth-bound plants, he covered his flat torch-down roof with mosses, lichens, and ferns mostly collected from his forest property these are largely epiphytes (air plants), which don’t require soil. And in the forests of Washington’s Olympic Peninsula, architect Roy Hellwig of Sequim also gave local natives a try. In Phoenix, for instance, landscape architect Steve Martino took a playfully literal approach, laying prickly pear pads like shingles on 3 inches of native granite soil on a low, flat, reinforced roof. Yet with lowered financial expectations comes more design freedom, and a growing number of residential green roofs display plant surprises, innovation, and a delightful sense of experimentation and fun. A smaller residential roof may accomplish some of the same environmental goals, but full financial payback is unlikely at least in the near future these projects are more about doing good for the environment, beauty, and horticultural interest. Most of these projects, like the Academy’s, are standard “extensive” green roofs as now defined: vegetation growing in a shallow (3- to 6-inch) layer of lightweight soil medium, contained in a special assembly system over a waterproof membrane. Green roofs have become natural fits for many public buildings as well, thanks to large-scale environmental and financial benefits such as energy efficiency, storm-water management, sound insulation, and the development of habitats for birds and other urban creatures. In Virginia, Norfolk Botanical Garden’s green roof uses sedum, delosperma, and sempervivum.

Eco green roofs