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Weighty Issue: Project Planners Wrestle with Roof's Load


A 2011 reroofing project at Arizona State University presented maintenance and engineering managers with a complex and related set of challenges. The project at the Wells Fargo Arena, one of the campus's largest buildings, coincided with the university's growing commitment to solar power. During the $2.5 million project, roofing crews contended with a tight deadline. They also had to work in challenging weather conditions and coordinate with other projects at the arena.

None of those hurdles, however, matched the challenge of preparing the roof and the structure below it for the installation of more than 2,000 solar panels. The added weight of the solar panels added an unusual component to the team's specification considerations for the re-roofing project.

"Usually, our first choice in roofs for our environment is a coated, built-up roof like three-ply, but that would have been too much weight with the solar system on the roof structure," says Bob Backus, the supervisor of carpentry services, the campus department that oversees roofing projects. "We decided on a PVC (polyvinyl chloride) roof, a product we like and use a lot on campus, particularly with our solar installations."

The PVC system is lighter than other roofing systems, a feature that enabled the roof and its support structure to handle the additional weight of the solar panels, as well as the banners and scoreboards hanging inside the arena.

"It came down to us having the lightest weight that we can put on it," says Luke Ngo, a capital programs project manager. "We had to recalculate the load and recalculate what can hang after the solar panels were installed."

The most challenging part of the installation process was making about 1,800 penetrations into the roof membrane to secure the solar panels. The task forced crews to work double shifts and speed up the project to meet the November deadline for the solar system installation.

"We had 1,800 holes through the roofing insulation that had to be made, resealed, and repacked with insulation," Edelhoff says. "That's 1,800 holes through a roof that had to remain watertight. It took a while."

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