Green roofs, also called living roofs or eco-roofs, consist of a complete system of vegetation, growing medium, drainage, and a waterproof membrane. Ranging from very lightweight systems with shallow succulent plantings to deeper, heavier systems supporting a variety of plantings, they are greening roofs in the Richmond area.

This green roof grows atop a condominium high-rise in downtown Evanston, IL. Notice the variety of plant material and the covered seating area.

While the introduction of landscape architecture onto a building's roof is not new, modern-day installation techniques have improved, and the environmental, economic, and green building benefits can be tremendous. The technology is currently viewed as both practical and economically feasible.

Matthew Carr, the eastern regional manager for American Hydrotech Inc. and member of the board of directors of the James River Green Building Council, describes this technology as a way to transform the roof into a storm water detention site. Whether extensive or shallow, a typical green roof system can retain up to 50 percent of a one-inch rainfall, which is significant in relation to the overall reduction of rainwater runoff from a building site.

"One of the largest environmental benefits of a green roof and most immediate return on investment for property developers is the storm water management benefits, which reduce the quantity of water runoff from the building site and improve the quality of the remaining water. Green roof technology can play a key role in the smart growth or new urbanism strategies that strive to lessen the environmental impact of new structures," says Carr.

Government, industry, and the American Institute of Architects are enacting requirements and standards to promote the development and use of environmentally friendly building practices. "The challenge facing the design community," says Carr, "is to take the second building site, the roof, and do something positive with it in relation to the environment. The Germans, having understood this concept for almost 30 years, have enacted laws requiring green roofs in cities like Berlin and Stuttgart. A good friend and pioneer of green roof technology in the U.S. is Ed Snodgrass, a horticulturist located in Maryland. In September, Ed is participating locally as a speaker on this topic during the Virginia Garden Festival. It is horticulture researchers like Ed who have influenced cities such as Chicago and Seattle to incorporate green roofs as a design requirement for their new buildings. These cities recognize that this technology is a way to mitigate storm water runoff, reduce the urban heat island effect, and cool the microclimate. It also creates a wildlife corridor for native species and creates a carbon sink that actually absorbs atmospheric pollutants."

	Matthew Carr (left) and colleague Mike Maloney of American Hydrotech Inc. stand before a green roof installation at the Manulife Financial headquarters in Boston, MA.

Another form of a living green technology is the roof garden. Richmond's Massey Cancer Center's healing garden is one example. "This style garden," says landscape designer Shelley Arthur, owner of Shelly Arthur Landscape Design LLC, "can vary in size but should first and foremost consider the needs of those who use the site." Rosemary Alexander, founder and principal of The English Gardening School, agrees with Arthur and advocates that all designs start with owner requirements and consider the structural elements of the site. Finally, designs should focus on environmental influences, space, light, scale, and proportion.

A third form of green roof technology promotes the use of roofing materials that are either derived from recycled materials and/or provide significant reduction of onsite energy consumption. For example, the Energy Star program is designed to encourage the use of building materials that contribute to the overall efficiency of heating and air conditioning systems. To encourage consumers to consider implementing green building strategies, tax incentives are available.

There is some question about the benefits of green roof technology applied at the residential level. "Recently," Carr says, "while I was in Philadelphia, a state official from the department of water told the Delaware Valley Green Building Council that Philly is considering taxing property owners on the amount of impervious space they own, since rainwater runoff from it is forcing the city to increase the size of its storm systems. Strategies like green roofs are a way for property owners to reduce their impervious area and lower their taxes. Because installation techniques have improved, the current technology is viewed as both practical and economically feasible."

THE VIRGINIA GREEN Industry Council's second Virginia Garden Festival will be Sept. 22 at Lewis Ginter Botanical Garden, 1800 Lakeside Ave. in Richmond. Call (804) 262-9887 or visit virginiagardening.com/virginiagardenfestival.htm for more information.