Page E1.2 . 28 February 2007                     
ArchitectureWeek - Environment Department
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Environmental Center in Georgia

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Starr continues: "We chose a site with a dry ravine, and the building took its form in part from this site. The building spans the ravine, but more important, the ravine became a cascading water feature that draws nonpotable reuse water from the nearby Gwinnett County wastewater treatment facility and uses it to provide air conditioning. Nonpotable reuse water is also used for irrigation and flushing toilets."

The building's energy- and water-saving strategies are extensive as they must be in any project targeted for LEED-Gold. The building envelope is well insulated and tightly constructed to prevent heating and cooling losses; 8-foot (2.4-meter) overhangs protect the large windows from solar heat gain; and the building features daylighting and natural ventilation.

Water-conserving plumbing fixtures are expected to save 316,000 gallons (1,200 cubic meters) of potable water annually. Pervious paving in walkways and parking lots allows water to seep into the ground instead of running off into storm drains.

Excess storm water flows into vegetated bioswales and constructed mini-wetlands to help contain onsite surface runoff. These strategies allow water from heavy rainfall to replenish underground aquifers instead of flooding overburdened streams.

Green Slopes

What is most unusual, however and a contributor to both water and energy conservation is the 40,000-square-foot (3,700-square-meter) vegetated roof, thought to be the largest sloped green roof installation in the United States. It covers the entire building, adding insulation, reducing the cooling load, and providing a natural habitat for insects and other wildlife.

The roof is planted with six species of drought-resistant flowering sedum, which requires minimal maintenance. This planting will reduce the quantity and improve the quality of storm water runoff.

Most of the green roof is sloped at a pitch of 4:12, or 18 degrees. Steel columns and wood trusses on 4-foot (1.2-meter) centers support a design load of 35 pounds per square foot (1676 pascal).

The first layer of the roof's construction is a deck made of concrete and rapidly renewable aspen wood fiber, chosen for its ability to mitigate noise inside the building. Over this roof deck is sheathing made of fiberglass and reinforced gypsum, providing a smooth surface on which to apply the membrane roofing.

The roofing was applied directly to the sheathing as a hot, fluid, rubberized asphalt membrane. This was covered with a high-density polyethylene protection sheet to act as a root barrier.

To add thermal insulation, the next layer is an "inverted roof membrane assembly" (IRMA) with 3 inches (8 centimeters) of Styrofoam made of extruded polystyrene. Over that is a drainage mat, the same type as that used between the building's concrete walls and the recycled granite stones that clad the building's exterior.

A "cellular confinement system" was applied over the drainage mat to help stabilize the soil on the sloping roof. This is a system of perforated polyethylene strips joined in accordion fashion to form a dimensional mesh. Then, specially engineered 4-inch- (10-centimeter-) deep growing medium was blown into the cellular confinement system.

The flowering sedum was planted in this medium. It will be watered for one year and thereafter is expected to be maintenance-free except during times of drought.

Add Delight to Design

In this climate, even a green roof sheds rainwater, and the architects were faced with the challenge of channeling water from an undulating roof. They built crickets in the interior valleys to direct excess water to the overhang areas. But instead of channeling the water into conventional downspouts, they came up with a solution that furthers the educational mission of the Gwinnett Center.

Below each outlet, spaced at column centerlines, are copper "rain chains" that direct the runoff to bioswales below. These attractive elements draw attention to the existence and the path of storm water, providing a further interpretive element for building visitors.

Inside the building are classrooms, interactive science exhibits, a small theater, a library, and a lecture hall. In these spaces, visitors learn about their relationship with water and the rest of the natural environment. But another way for them to learn is to look outside to the surrounding landscape and the to building itself, where the medium is the message about environmental sensitivity.

The GEHC is a collaboration of the Gwinnett County Board of Commissioners, the Gwinnett County Public School System, the University of Georgia, and the Gwinnett Environmental & Heritage Center Foundation. In February 2007, Lord, Aeck & Sargent Architecture became one of the first architecture firms in the United States to adopt The 2030 Challenge.

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Project Credits

Architect: Lord, Aeck & Sargent
Landscape Architect: The Jaeger Co.
General Contractor: Juneau Construction
Structural Engineer: Uzun & Case
MEP/FP Engineer: Newcomb & Boyd
Energy Consultant: RMI/ ENSAR Built Environment Team
Civil Engineer: Lose & Associates
Exhibit Designer: Van Sickle & Rolleri
AV and Acoustics Consultant: Waveguide Consulting
Signage Consultant: Huie Design
Roofing Trade Contractor: Metro Waterproofing, Inc.
Landscape Trade Contractor: ProLandscapes LLC
Green-Roof Components: American Hydrotech, Inc.

AW

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Green-roofed Gwinnett Environmental & Heritage Center in Buford, Georgia, designed by Lord, Aeck & Sargent.
Photo: Jonathan Hillyer/ Atlanta

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Recycled granite clads the building's exterior.
Photo: Jonathan Hillyer/ Atlanta

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Section through green roof.
Image: Lord, Aeck & Sargent

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Green roof layers.
Image: Lord, Aeck & Sargent

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Deep overhangs with rain chains.
Photo: Jonathan Hillyer/ Atlanta

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Functional and decorative rain chain.
Photo: Jonathan Hillyer/ Atlanta

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Formerly dry ravine, now a water feature.
Photo: Jonathan Hillyer/ Atlanta

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Daylit interior.
Photo: Jonathan Hillyer/ Atlanta

 

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