Aerosealing the Deal

By Karl J. Paloucek

Outside view of the tent and injection tubing integral to the Aeroseal process in outdoor environments under adverse conditions.

One of the long-term challenges facing any building manager or chief engineer is the maintenance of ductwork on the property to prevent leakage. It’s a problem that can affect even newly installed ventilation systems. Leakage, in this business, equals inefficiency, and inefficiency equals cost. But mitigation has often been an inefficient problem in itself.

We talked recently with John Muller, president and owner of Airways Systems, and Joe St. Pierre, sales and project manager, about their solution to sealing ductwork and bringing it up to peak efficiency.

“When Joe and I, and my duct-cleaning salespeople went to the St. Patrick’s Day Chief Engineers event,” Muller recalls, “One chief after another would say, ‘How come I’ve never heard of this?’ And the answer is that despite the fact that there have been commercial jobs since 2004, for whatever reason, in the Chicago area — and frankly, a lot of other places in the country — it hasn’t been that aggressively marketed.”

The process goes by the name Aeroseal, and at least in concept, it’s as simple as it is innovative. According to St. Pierre, it begins by isolating everything — the vents, the VAV boxes, air handlers and rooftop units, etc. — from the system. “We take the ductwork and we isolate it — we blanket everything off,” he says. “We cut a hole into the ductwork, take our equipment and hook up a temporary duct to the equipment, and we pressurize the ductwork. We basically pump air into the duct system.”

Because the duct system is otherwise sealed, any air pumped into the ductwork has only one way out, and that’s through any leaks in the system. This is where the magic happens: “Now, what I’m going to do is introduce a sealant into that air,” St. Pierre says. “The sealant is called vinyl acetate polymer. Broken down, what that is, is the main ingredient that Wrigley’s uses in chewing gum. It’s a water-based material. It’s also one of the ingredients that they use in baby pacifiers, believe it or not. It’s a safe material.

“The liquid gets converted from a liquid to an atomized form — like a vapor,” he explains. “So now the vapor is carried with the air, driven to the holes. As it escapes out of the holes under high pressure, the polymers escape out of the holes. As they begin to escape out of the holes, they begin to coagulate, build up — clot, if you will — around the edges of the openings as they’re trying to escape, and then they start to seal. It’s kind of like if you cut yourself on your arm. It clots and builds up and stops, essentially.”

Once sealed, the vinyl acetate polymer stays in place and resists the weathering that can break down other sealants, like caulk, mastic or duct tape. “It stays soft, and it doesn’t dry, doesn’t crack,” St. Pierre says. “It doesn’t act like caulk — caulk eventually starts to peel away, like it does in your tub. It stays soft, so it withstands the moisture. It withstands the hot, the cold, the moisture, the vibration, expansion and retraction.”