Duct-sealing equipment ensures HVAC construction of medical center stays ‘green’
Duct-sealing equipment ensures medical center stays cool, ‘green’.
The Arzanah Medical Complex in Abu Dhabi, capital city of the United Arab Emirates, contains two 5-story structures with a 223,000-square-foot hospital and a 97,000-square-foot clinic.
The center was designed to be a gold-level structure under the U.S. Green Building Council’s Leadership in Energy and Environmental Design rating system.
Just weeks before the facility was to open to the public, however, readings taken from several of the structure’s HVAC risers indicated that leaks were robbing the facilities of as much as half of the air traveling through the ductwork. Not only was this unacceptable for LEED certification, it also created significant concerns regarding indoor air quality, building performance and energy costs. Clearly, something had to be done — and soon.
The structure’s interior walls were already in place, eliminating direct access to the ductwork and making traditional sealing methods impossible without first demolishing the newly built walls. Engineers tried lowering workers down the risers to find and manually seal the leaks, but this proved both hazardous and ineffective.
Desperate to find an alternative solution to this potentially project-crippling problem, the building engineers began an Internet search for an answer. There they came across an article about a new duct-sealing technology called Aeroseal. It was developed with partial funding from the U.S. Department of Energy to solve a critical issue related to home and building energy waste: leaky air ducts. The engineers learned that, unlike traditional approaches to duct sealing, the technology works from the inside of the duct to seal leaks. They found that Aeroseal had been used to seal duct leaks at other medical facilities such as the University of Ottawa Heart Institute and Nemours Children’s Hospital in Orlando, Fla. And if it truly sealed leaks from the inside, then they would be able to fix problems throughout the entire duct system without disturbing the finished construction.
An Aeroseal team was flown the 7,000-plus miles to the worksite to demonstrate the technology on several leaking risers.
“Aeroseal passed all our criteria,” said Gus Heber, construction director at Habtoor Leighton Group. “First, it proved safe for use, even in a hospital environment. It then proved highly effective at sealing the system leaks.”
The Aeroseal process begins by blocking the wall registers so that air can only escape through the leaks in the ductwork. The duct system is slightly pressurized, increasing in pressure during the sealing process. The sealant is than heated up and blown into the shafts through an existing access point or through a temporary entranceway cut into the system. The dry, 7- to 10 -micron-sized adhesive particles remain suspended in air as they travel throughout the ductwork until they reach a leak. Then they begin to accumulate around the leak, bonding to other sealant particles until the entire hole is permanently filled.
Unlike some sealants such as those used for weatherization or material bonding, the Aeroseal sealant is a vinyl acetate polymer with a rapid, two-hour cure rate. The sealant exhibits minimal off-gassing of volatile organic compounds and its nontoxic properties afford it no Occupational Safety and Health Administration
“Aeroseal was so effective at eliminating leaks in the initial 15 risers we targeted for sealing, that we decided to expand the project to include the building’s entire
HVAC system,” Heber said. “We then use it to seal the lab exhaust system, kitchen exhaust system and smoke extract system — a 127,000 cfm (cubic feet per minute) project in total.”
Aeroseal completed the entire sealing project in less than two weeks. Post-sealing testing showed that there was less than 5 percent leakage in the entire system — well below the LEED certification requirements.
“I thought the Aeroseal technology was fantastic,” said testing and balancing technician Kevin Waite of Trent Technical Services. “I was expecting to find the entire inside of the ductwork coated with sealant. In fact, it just gathered around the holes to seal the leaks and left most of the internal ductwork free from sealant.”
The Arzanah Medical Complex in the United Arab Emirates used equipment from Aeroseal to ensure it maintained its green building certification.