Green Buildings--going beyond the checklist.

Those in the architectural industry tend to use the terms "green" and "sustainability" interchangeably when describing buildings that are environmental friendly. They also rely on the LEED (Leadership in Energy and Environmental Design) Green Building Rating System to measure a building's greenness. The LEED Rating System, although useful as a guideline for environmentally responsible design, is more a checklist of individual items than a true design approach. But what if the architectural industry looked beyond the checklist approach to focus on creating structures that contribute in a more active way to a building's greenness?

For structural engineers like myself, it is already standard practice, for example, to require the use of post-industrial materials. We regularly replace Portland cement in concrete with fly ash, a byproduct of coal-combustion in electric power plants, and with blast furnace slag, a byproduct of the manufacture of iron. We also specify that structural steel be produced from recycled steel material. Although such practices are significant, sustainability requires a more comprehensive approach.

Weidlinger Associates and some other firms have already taken such an approach. Weidlinger recently collaborated closely with the design team for the Queens Botanical Garden's new administration building in Flushing, New York, to develop a roof canopy structure that would not only provide shade for events, but also collect rainwater for garden irrigation. This project won the 2004 NYC Green Building Design Competition for "excellence in the use of good design principles and the integration of green building technologies." Weidlinger studied several architecturally stunning structural schemes that could function as rainwater collectors. These included a series of inverted cones constructed of Teflon-coated fiberglass fabric, cables, and steel that would funnel the rainwater to reservoirs. That scheme was eventually replaced by a sloping steel folded-plate structure that acts as a trough, directing rainwater to collectors at the column bases.

One of Weidlinger's core philosophies is to design structural systems that minimize the use of material. This happens to be a green approach; it just wasn't called that in the late 1980s, when the firm designed the roof of the Georgia Dome Stadium. The Tenstar Dome, an innovative tensegrity-based roof structure, is a fraction the weight of a conventional roof structure. The translucent Teflon-coated fiberglass fabric roof membrane minimizes daytime lighting requirements, reducing the stadium's energy consumption.

In other successful designs, engineering firms have moved the primary structure to the building's exterior, reducing the volume of interior air that needs to be conditioned, and pumped hot water through the structural pipe columns, creating giant radiators. As long ago as 1959, the steel structure of Penn State University's Beaver Stadium was disassembled and moved to the other side of campus, where it was reassembled and expanded.

The next step for the architectural industry is to look beyond the checklist approach to green design and examine how buildings interact with nature--how they live--to create a truly green built environment. Perhaps one day, buildings will contribute to the environment rather than deplete Earth's natural resources.

By SETH WOLFE, PE

WEIDLINGER ASSOCIATES, INC.