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Special to Georgia Public Policy Foundation Newsletter
September 12, 2003
Eva’s Penthouse View Made Better By Green Roofs
By Robert Ryan
A generation of television viewers heard the glamorous Eva Gabor exclaim “I just adore a penthouse view!” during the title scenes of the popular 70’s situation comedy Green Acres. Imagine how robust her enthusiasm would have been could she have gazed upon something more beautiful than a landscape of asphalt, tar and litter strewn roofs.
Today, green roof design has empowered architects, landscape architects and urban planners with new ammunition to combat the blight of gray urban landscapes. The environment – and summer temperatures – are all the better for it.
Green roof design is the wave of the future to mitigate urban and suburban impervious surfaces. Green roofs entail more than putting lawns on top of buildings; it’s a way to improve the environment and our quality of life while creating pleasing urban landscapes.
Green roofs today are an innovative and flexible solution that can simultaneously provide benefits for the urban ecology, and for building owners by increasing property values. Green roofs involve a system of special waterproofing membrane, a drainage/retention system, a specific growing medium and a project-specific palette of plant materials. Green roofs systems can be built as a system of components, or may be a prefabricated modular system.
The idea is catching on in North America as designers and developers are noticing the significant environmental benefits demonstrated by both the longer track record in Europe and some local projects.
One local example employing green roof strategies is the Turner Entertainment Group’s campus. In their first phase, a pre-development, 2.2 acre urban parking lot was transformed with an intensive green roof plaza and gardens linking new and existing facilities.
Atlanta, shown through a NASA study, has a significant urban heat island effect. The Turner green roof demonstrates significant strategies to alleviate this problem. Surface parking was eliminated and placed under the green roof. The landscape plaza reduces high temperatures and, in turn, reduces potential increases in ozone. Storm water runoff is intercepted, delayed and absorbed in the landscape and returned back into the atmosphere through evaporation and transpiration. The runoff that passes through the green roof system is filtered before it enters storm water and stream systems.
Like the Atlanta project, green roofs provide numerous benefits for the environment in addition to natural beauty. Green roofs have dual impacts when rainfall hits the surface. Storm water control, may reduce the need for detention facilities; reducing the amount of land used or defraying storm water treatment costs. Rainwater carries airborne pollutant particulates to the ground. The green roof can filter particulates out, before they can run-off and pollute our waterways. Additional ecological benefits include improving outdoor air quality through reducing the urban heat island effect, lowering temperatures and reducing ground-level ozone caused by smog and higher cooling loads. Also, dust and pollutants are bound by the plant foliage and increased oxygen is provided through photosynthesis by the plant material.
Benefits attractive to building owners that are quantifiable include extended roof membrane service life; sometimes by a factor of at least two, often three. A green roof can reduce cooling loads and generally improve the function of conventional insulation, reducing energy consumption.
Perhaps, one of the most important benefits green roofs offers, though hard to quantify, is the positive impact on the quality of life in our urban environments. Plant life actively suppresses noise while the green space offers visual and aesthetic interest, recreation opportunities and positive psychological effects on the human spirit.
However, for all of the advantages come some concerns. The greatest concern about green roofs is leaks. Manufacturers have greatly improved the quality of waterproofing membranes and created total green systems.
Despite improved manufacturing and installation methods, costs still limit the use of green roofs. Realistic costs for extensive green roofs range from $15 to $20 per square foot, including everything from waterproofing to plants. Key considerations for implementing green roofs include structural capacity, waterproofing, water or drainage systems and plant selection. As the various benefits resulting from green roofs are better understood (storm water detention, urban heat island mitigation, energy savings, adding project’s value), they will ultimately outweigh any negative hype placed on this technique.
When considering a green roof, designers and developers should take into account the long term cost savings. The most significant benefits of green roofs, such as storm water retention and a healthier microclimate, combined with the improved roof longevity and thermal insulation of a green roof, can easily outweigh the increased first costs for most installations.
Green roofs present a unique business opportunity to bring cities to life by combining environmental responsibility, life–cycle economies, the urban ecology and an increased quality of life through plants, water management and reducing impervious land uses, as the Turner Entertainment Group Campus demonstrates. Nature is at premium in the urban setting; the project introduces additional ecologically and psychologically valuable green space to the campus.
Cities often effectively exclude greenery and nature. Green roofs are no substitute for open space and simply cannot replace the significant functions of forests, rolling green hills and open fields, they do provide green space, visual and aesthetic relief and wildlife habitat from which both urban and suburban areas can greatly benefit.
Bottom line, if green roof design had been widely practiced in Eva’s New York City, Mr. Douglas may have never gotten her to that dubious little farm near Hooterville.
Robert S. Ryan is a registered landscape architect at the landscape architecture firm HGOR. He has
over 20 years experience in creating cutting edge designs that respond to the social, environmental
and economic issues faced today.
HGOR is a nationally recognized firm that embraces the challenges of creating places of social value, economic sustainability and environmental stewardship. With a staff of planners, urban designers, landscape architects, environmental specialists and support staff, HGOR focuses on quality service and innovative solutions to complex design issues. For more information, visit www.hgor.com.