Green Roofs - Living Architecture Monitor - Winter 2009 - (Page 19) “The tall vines, with their watersucking roots, undoubtedly also contribute to lessening stormwater runoff from the property.” mer.” However, it is safe to say that the vines act in much the same way that closing shades in summer and opening them in winter saves energy. Johnsen adds, “they may save more energy than shades in the summer, because they are actually in front of the building, instead of inside, as shades are. With shades, there is still some heat build-up between the shade and the window.” The tall vines, with their water-sucking roots, undoubtedly also contribute to lessening stormwater runoff from the property. The maintenance of the green wall has been relatively minimal. Because all the vines are native to the area, they are well-adapted to the local soils and northern Virginia’s blistering summers. They do not normally need to be irrigated, although Johnsen says that they were occasionally watered at ground level with a regular garden hose in one or two of the very dry summers. Also, during the first few growing seasons, when the vines were getting started, maintenance workers would help with weaving the vines into the trellis. Now, Johnsen says, the opposite problem exists attracted to the light reflected off the windows, the vines sometimes grow aggressively into the six-feet-wide space between the building and the trellis. To keep open space between the trellis and the building, maintenance workers must occasionally trim the vines down with long-poled lobbers. Eight years later, it is fair to say that the National Wildlife Federation headquarters building successfully achieved the goals of the organization to minimize impact on the local environment and wildlife. The bioretention ponds serve to filter runoff from the building and parking lot, while simultaneously providing wildlife habitat. The building affords its staff wildlife viewing opportunities unusual for a suburban office park and the green wall creates vertical wildlife habitat and energy savings for the building. D Roxanne Nersesian Paul is a senior coordinator for the Habitats Program at the National Wildlife Federation in Fairfax,Virginia. http://www.xeroflora.com http://www.xeroflora.com
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