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April 16, 2009

Going green: Green roofs

The growing season is fast approaching and as backyard gardeners prepare their plots for spring planting, Pitt is too, with some green spaces planned for some high and unlikely places.

A 10,000-square-foot green roof is under construction as part of the Swanson School of Engineering’s $100 million Benedum Hall renovation and expansion project.

Layers of materials for waterproofing, insulation, drainage and soil filtering are in place beneath a 4-inch layer of lightweight soil mix made up of organic and mineral components that was hauled by crane onto the roof atop the existing Benedum Hall auditorium.

As soon as temperatures permit planting, hardy, low-maintenance plants will complete what is known as an “extensive” green roof — one that needs no irrigation system and is essentially maintenance free, said project engineer Jeremy P. Fusaro of P.J. Dick Inc.

Exactly what will be planted remains at the discretion of University Architect Park L. Rankin.

Rankin said sedum will dominate. Gold moss, crooked yellow, two row and watch chain sedum varieties are among the choices, but a full list of the plant varieties has yet to be selected. The plants will be arranged informally to take advantage of the variations in leaf and blossom colors and of the varying times different varieties bloom, Rankin said. “These are more or less native plants that are tolerant to wet weather and drought, so depending on the rainfall, this will determine the lushness of the vegetation and blooms.”

The auditorium roof will have no public access, but graduate student spaces on the third floor of the new Mascaro Center for Sustainable Innovation will look out over the green space.

A second type, or “intensive” green roof is planned for the plaza between the structures. The 3,000-square-foot space will be planted with grass and, unlike the auditorium roof, will need an irrigation system and regular mowing, Fusaro said. It is expected to be in place when students return for the fall term.

On Pitt’s upper campus, the addition to the Falk Laboratory School also includes a green roof. It is scheduled for planting in May, said school director Wendell McConnaha.

Fusaro, who earned a bachelor’s degree in mechanical engineering and completed a master’s in civil engineering at Pitt, said the main reason for using green roofs is to reduce the construction footprint of new buildings. “You put back as much green space as you’re taking away,” he said, noting that Pitt’s project is somewhat unusual in that parts of the existing structures are being topped with green roofs.

Adding a green roof earns points toward Leadership in Energy and Environmental Design (LEED) certification, a set of standards for sustainable construction developed by the U.S. Green Building Council.

The building council currently lists 32 LEED-certified projects in Pittsburgh, including Pitt’s McGowan Institute for Regenerative Medicine (See Oct. 25, 2007, University Times).

Installing a green roof means more up-front costs — in part due to the labor required to put down the additional layers of material that are required. Industry sources estimate green roofs can cost nearly 40 percent more than a typical thermoplastic polyolefin (TPO) membrane roof — $25 per square foot compared to $18 for the TPO material.

However, green roofs offer multiple environmental benefits, Fusaro said. They cut noise and help reduce the urban “heat island” effect that causes city temperatures to be higher than their surrounding areas. The plant material insulates the roof, saving utility costs by leaving the building beneath it cooler in summer and warmer in winter.

Green roofs also help reduce storm water runoff, retaining between 50 and 90 percent of a typical rainfall, according American Hydrotech, which is supplying the Benedum project’s green roof system.

“Pitt has been a pretty good proponent of green construction,” Fusaro said. “This is the future here,” he said.

—Kimberly K. Barlow

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