Two New Books on Green Roofs

Planting Green Roofs and Living Wallsby Nigel Dunnett and Noël Kingsbury. Timber Press, Portland, Oregon, 2004. Hardcover, 264 pages, $34.95.

Green Roofs, compiled by staff at the Earth Pledge Foundation in New York City, is probably the better book to read first if you are new to this design strategy. The book begins with a few pages of introductory information, including a foreword by architect William McDonough and a succinct overview of the environmental benefits of green roofs by Earth Pledge staff and green roof consultant Katrin Scholz-Barth.

Following this introductory material, the bulk of the book provides 40 superbly illustrated, two-page spreads of green roof case studies. These case studies were selected from around the world, with 15 countries represented, including eight projects from the United States, seven from Germany, five from Switzerland, four from Japan, and three from Canada. Each case-study spread includes several paragraphs of description, three to five color photographs, and consistently formatted data that includes location, completion date, architect, landscape architect, specialized green roof consultants, green roof area, and soil depth. (Even more information on each case study is provided in an appendix—including, for most projects, green roof component manufacturers, type of roof membrane, soil medium, plants used, planting method, construction cost per square foot, and weight per square foot.) These case studies demonstrate the tremendous breadth of green roof systems and the design opportunities green roofs provide.

The most interesting project to me was an unintentional green roof in Zurich, Switzerland, that was completed in 1914. A reinforced concrete water-filtration plant was topped with gravel, sand, and eight inches (200 mm) of topsoil from the surrounding farmland to keep the water cool. The roof naturally vegetated over a period of years and today includes more than 170 plant species, including nine orchids that are now rare or endangered in the region. Among the orchids are 6,000 specimens of

Orchis morio, a species thought to be otherwise extinct in the Zurich area!

Following the building case studies are 30 pages of municipal case studies describing efforts to advance green roofs in Berlin; Tokyo; London; Portland, Oregon; Chicago; Toronto; and New York City. In many ways these municipal case studies comprise the most interesting part of the book. We learn how Berlin really launched the modern green building movement and how very different priorities in the other cities are driving green roof implementation. For example, Tokyo is concerned with providing open space, London with creating habitat for an endangered bird, Portland with stormwater management, and Chicago with urban heat-island mitigation.

Green Roofs. Don’t be misled by the title;

Planting Green Roofs is much more than a book about plantings. Close to half of the book provides an excellent overview of green roofs, including historical background, detailed information on the benefits of green roofs, and specifics on the various components of green roofs. This is the best overview I’ve seen on green roof design and systems—and it goes into significantly greater detail than

Green Roofs.

Then, true to the book’s title, it includes extensive information on appropriate plant selection for green roofs. Rather than simply listing plants, however, the authors explain why certain plants make sense in the harsh, xeric environments found on rooftops. To date, most green roofs are dominated by sedums and related succulents from Europe—largely because the green roof movement developed in Europe. There is very interesting discussion about what sort of native plants in North America might be appropriate for green roofs—and why.

In addition to covering green roofs, the book also addresses living walls—the use of vines, specially pruned trees, and other plantings to cover building façades with vegetation. Benefits of green façades include controlling solar heat gain, trapping or removing dust and other pollutants, protecting walls from heavy rainfall and hail damage, providing visual appeal, and offering forage and nesting habitat for wildlife. On unoccupied buildings, noise-control barriers, and retaining walls, the aesthetic benefits may be most important. (Potential

damage to walls from the adventitious roots of vines is not addressed by the authors, but can be a concern.)

This practice of greening building façades is far more common in Europe (especially Germany and France) than it is in North America—though the northeastern U.S. certainly has its share of ivy-covered buildings (think Ivy League universities)! In addition to self-clinging vines like English ivy and Virginia creeper, the book addresses the use of support systems to allow other plants to serve a similar role.

Clear color photos throughout

Planting Green Roofs complement the informative text. The book concludes with a 40-page directory of plants for roof and façade applications and a several-page list of suppliers of green roof systems and components.

If you’re interested in green roofs, these two books provide a superb starting point!

–AW