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A local builder tries on a new, faster way of insulating buildings

ADDISON COUNTY — The field of building science changes dramatically and rapidly. Nearly every day, new products, techniques and methods are introduced that challenge the ways buildings are constructed and introduce potentially more effective and efficient solutions. Not only can these advancements help buildings perform better from an energy usage perspective, but they can introduce time and cost savings and reduce waste.
However, as with most things new, there are unknowns and could be hidden risks that make early adopters vulnerable.
One of these newer technologies addresses the need for contractors to seal buildings so they don’t leak much air.
Sean Flynn is co-owner of Silver Maple Construction, a firm that specializes in high-end, custom residential building, based in New Haven. Silver Maple projects adhere to very strict energy standards and therefore crews have been perfecting the art of air sealing using specialized tape, vapor barrier paper, spray foam and caulk for years.
Air sealing budgets for residential projects often are some of the hardest numbers to swallow, Flynn says, easily reaching $15,000. Plus the project can take weeks to complete. It’s a tedious process ripe for human error and imperfection, since it relies on workers manually sealing air gaps that are often in hard-to-access joints and seams.
That’s why Flynn was immediately intrigued (and skeptical) when he heard about AeroBarrier. Marketed as a “breakthrough envelope sealing technology,” AeroBarrier is an aerosol air sealing system that is blown into a home while the space is pressurized during a blower door test. It can be performed either after the exterior sheathing and all outside penetrations are complete up against that outside plane, or up against sheetrock to the inside of that innermost plane. (Flynn prefers the latter, saying that he is more comfortable with the air barrier to the inside of the insulation so as to avoid any risk of dew inside the wall that could create a “mold sandwich.”)
The house is pressurized using a blower door method to about 100 Pascals of pressure. Tripods are set up inside the house with tubes containing the patented acrylic caulk that lead to the rig that’s outside. Once the switch is flipped and the appropriate pressure is reached, the “emitters” begin to spray, releasing a fine mist into the air.
“From there it’s like a water balloon with pin pricks in it that’s being squeezed,” Flynn says. “Because of the pressure the caulk is attracted to those areas where there’s a gap in the pressurized cavity.”
The caulk efficiently finds gaps and quickly fills them, tiny fibers within the material interweaving as it fills holes and plugs leaks from the outermost point in. It does not stick to vertical surfaces, so stays clear of walls or other vertical planes, creating messes only on horizontal ledges such as windowsills or floors (which can either be covered or wiped clean immediately after application).
Operators from the outside watch through a computerized interface as the ACH50 number drops. (ACH50 stands for air exchanges per hour measured at 50 Pascals of pressure differential.) The process is complete when the desired ACH50 number is reached and the switch is flipped off. You can’t always see the caulk joints, Flynn says, which at first made him wary, but that’s because the caulk seals from the outside in, using only as much material as is needed to fill the air gap.
“In most situations we can take a house from around 7 ACH50 down to below 1 in under two hours of spraying, with set up and clean up on either end amounting to another few hours,” Flynn said. That’s a far cry from the days or weeks it might have taken to paper and tape the same space. What’s more, the resulting ACH50 scores are far better than what they could have reached using older air sealing methods.
“To be honest I had little faith that it was actually going to work,” Flynn said. But he was interested enough in the possibility that he bought one of the first rigs available on the market. “I told them that I’d give it a try and if I didn’t like how it worked I was going to send it back,” Flynn said. “I thought it was going back for sure, but in fact it’s been amazing.”
The rig showed up last summer. At first, Flynn said they used it only internally on their own homes and buildings, until they really understood how to operate it and felt comfortable with the system. “The rig itself is a little cumbersome and the set-up is pretty clumsy,” he said. Once hooked up and going the results are amazing, Flynn says, but perhaps they are paying a small price for being early adopters with the rest of the process.
Due to challenges operating the equipment in extremely cold temperatures, the number of projects they have completed using AeroBarrier technology is just around 25 or 30, Flynn estimates, but, he said, “ask me in another week or two and that number might be up over 100.”
“We’ll be using AeroBarrier in any air-sealing project Silver Maple handles.”
The system is not appropriate for all projects and there will certainly still be a time and place for tape and even sprayfoam (a product Flynn says he’s trying hard to get away from). Because of the open-air process, it is not practical for a space that is lived-in during construction as it would require either covering or clearing out all belongings to avoid them being ruined by the spray.
Otherwise, Flynn says, there are few examples of projects that it wouldn’t work for.
Skeptics may have reason to question the longevity of this product, but rigorous testing on the product have yielded great results, suggesting it will perform at its peak for at least 50 years. That’s equal to or better than the other air sealing materials on the market, Flynn says. Some may also question the safety of this product as well. Flynn says that it’s definitely not safe to be in the space during application, since the caulk would stick to you and get into your nose, mouth and any other openings. However, according to AeroBarrier, after 30 minutes of depressurization the space is safe. The caulk itself is GreenGuard Gold certified, “meaning you can effectively eat it and be fine,” Flynn says.
Editor’s Note: Since purchasing the AeroBarrier system, Sean Flynn started a spin-off business from Silver Maple called Zone 6 Energy, which is a subcontracting company that takes the AeroBarrier system on the road. Demand for this new air sealing technology has taken them to New Hampshire, Maine and Massachusetts, completing projects ranging from Passive Houses to large multi-family buildings in Boston. 

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