Exterior Use, Humid Climate No Match for Elastomeric-Foam Pipe Insulation

Oct. 2, 2012
Engineer challenged to keep students' heads dry

Completed in 2010, the 55-acre, nine-building Center of Arts and Academics in North Charleston, S.C., is home to two magnet schools—Charleston County School of the Arts and Academic Magnet High School—that function separately, but share the cafeteria, administrative buildings, media center, and gymnasium.

Buildings on the campus are cooled with two 400-ton chillers, 36 ice-storage tanks, 12 chilled-water pumps, 325 variable-air-volume boxes, and 11,500 linear feet of HVAC piping. Well over 4,000 linear feet of that piping is housed in canopied walkways. Beneath the piping is a perforated ceiling, which is open on the sides.

“I was very concerned about the canopy,” Cole Owens of Owens and Associates Consulting Engineers Inc., who designed the chilled-water system, said. “I have never had my pipe above where people were walking and was concerned that pipe condensation might drip on people walking below.”

Given Charleston’s humid climate and the 36°F to 38°F water traveling through the outdoor pipes, Owens knew insulation would be critical. Fiberglass was ruled out because of its potential to become waterlogged.

“Fiberglass completely breaks down when it gets wet,” Owens explained.

Owens chose AP Armaflex closed-cell elastomeric foam from Armacell LLC.

“Armaflex ... doesn’t absorb moisture, so its insulating properties remain the same, even in the presence of moisture,” Owens said.

Dry and Intact
Two-inch sheets of Armaflex were used to insulate multiple runs of 12-in.-, 10-in.-, and 8-in.-diameter piping beneath 900 ft of canopy. Armaflex, which has a water-vapor transmission of 0.05 perm-in. and a thermal conductivity of 0.25 Btu in./sq ft/hour/°F, was hand-glued and taped to the piping.

It seemed like enough, but given the unusual application and this being his first time designing a piping system like this, Owens did not rest easy until the campus had gone through an entire cooling season with no reports of wet heads.

Nearly two academic years later, Owens has not been disappointed.

“With a high-profile job such as the Center of Arts and Academics, lack of performance was not an option,” Owens said. “As a consulting engineer, I have asked many material and equipment manufacturers to show me a successful track record prior to my specifying their product. Each day, Armaflex continues to perform in a very demanding exterior application in our extremely humid environment.”

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