Quenching the Built Environment's Thirst for Water

Designers deploy synergistic strategies to decrease demand and find new sources of supply
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From Architectural Record
Joann Gonchar, AIA

Beyond toilets and irrigation
Uses for nonpotable water are not limited to toilet flushing and irrigation. In a recently completed project for Southface Energy Institute, an Atlanta-based nonprofit that promotes construction of sustainable homes and workplaces, harvested rainwater is used for these typical applications but is also incorporated into the operation of the cooling system.

The Eco Office, an addition to the Southface Energy Institute's headquarters in Atlanta, has rooftop and underground cisterns that store storm-water runoff from a photovoltaic array and a green roof. The water is used for both toilet flushing and irrigation, and is part of the operation of the mechanical system.

Photo: © Jonathan Hillyer

 

The 10,000-square-foot, LEED Platinum building, dubbed the "Eco Office" because it is intended to demonstrate technologies appropriate for commercial construction, is an addition to a demonstration home built by the organization in 1996. The new structure, designed by Lord Aeck & Sargent, has a dedicated outdoor air system (DOAS) with a multistage evaporative cooler that makes use of harvested rainwater to help reduce the temperature of incoming air without adding humidity, explains Gregory Jeffers, a senior project engineer with local firm McKenney's, the mechanical system's design-builder. A spray system surrounding the building's rooftop heat pumps also relies on harvested rainwater and creates a cool microclimate around the equipment, enhancing its efficiency. The technology is one of several integrated energy-conserving strategies that should help the Eco Office exceed the performance of a code-compliant building by 53 percent.

In addition to serving as a consumer of salvaged water, mechanical systems can also provide a source of water that can be directed to nonpotable uses inside a building or on its grounds. One such source is the condensate produced by air-conditioning equipment, especially in hot, humid climates. Condensate is sometimes used directly within the mechanical system, as makeup water in cooling towers, or for flushing toilets or irrigation.

Somewhat surprisingly, condensate collection was not an appropriate strategy for the Eco Office project, despite Atlanta's hot and sticky climate. The building's unconventional cooling system makes little condensate, according to Jeffers. "Typically, the more energy-efficient a system is, the less condensate it produces," he says.

For Southface, as for almost any project that relies on thermoelectric power, this energy efficiency translates into water savings well beyond the confines of the building. Since electricity generation requires water, "we're not just saving resources locally, we're saving them regionally," says Jeffers.

 

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Originally published in Architectural Record
Originally published in October 2009

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