Weighty Decision Complicate Reroofing Project
May 5, 2015
The reroofing of the Wells Fargo Arena undertaken by Arizona State University in 2011 required the project's planners to weigh an unusual consideration in their planning: the added weight of solar panels installed as part of the reroofing.
"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, 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," says senior project manager Karl Edelhoff. "That's 1,800 holes through a roof that had to remain watertight. It took awhile."
The process required a deliberate approach on the part of installers.
"Picture a pipe coming out through the roof, a vent pipe or something," Backus says. "These supports went right through the roof and attached to the structure below. Where there were all these penetrations, they had to lay down the PVC first, cut that hole where that penetration was going to go, put the pipe in there, attached it to the structure, then patch over the top of the membrane with another layer of membrane."
Crews also had to add the university's logo to the roof, a process that took three months to complete.
The paint "had to be a certain product that was OK with the manufacturer so it wouldn't have a chemical reaction to the roofing membrane," Ngo says.