Innovations In Commercial Duct Sealing

by | Jun 14, 2016

While the JW Marriott hotel in Atlanta’s affluent Buckhead district has always been a model of elegance and luxury, owners of the 28 year-old building continued to struggle with high energy costs and musty odors that had been plaguing the building for years. A consultant brought in to evaluate the situation explained that leaks in the hotel’s ventilation shafts were responsible for inadequate exhaust. This, he said, was the root cause of both excessive utility bills, and a range of indoor air quality issues.

With the building’s long ventilation shafts embedded behind walls and obscured by pipes, wires and other obstructions, accessing and repairing the problem had proven to be logistically and economically impossible – so, for years, the problem had simply been ignored.

A Critical Concern

Research suggests that the Marriott is not alone in its struggle with leaky ductwork. The U.S. Department of Energy estimated that the typical commercial building in the U.S. today loses about 25% to 40% of treated air through leaks in the duct system. A recent survey conducted by the Building Commissioning Association found that 68% of engineers and building professionals believe that duct leakage rates of 15% or more are common. 75% of respondents said that these leaks are the cause of substantial energy loss.

Even newly built properties are, more often than not, plagued with leaky ducts – leaks that obstruct ventilation, reduce HVAC efficiency, significantly increase monthly utility bills and, in many cases, jeopardize entire construction projects.

Last year, Hyundai’s new U.S. corporate headquarters in Fountain Valley, California was nearing completion. Furniture was arriving and the finishing touches were being made to the interior of the 6-story 500,000 sq. ft. structure. Just weeks before the grand opening, building engineers learned that they could not get official sign off for the project because of excessive leaks in the structure’s four smoke evacuation shafts and the outside air shaft. The project came to a standstill while the engineers looked for a viable solution.

Understanding the implications that leaky ducts and ventilation shafts have for indoor air quality and energy consumption, the U.S. Department of Energy, along with EPA and others sponsored research at Lawrence Berkeley National Laboratory to develop a solution. The result is a game-changing approach to duct sealing that the DOE has called one of the most significant energy-saving innovations to be made available to consumers since the department was first established.

Unlike traditional manual sealing such as tape and mastic, the new approach comes in the form of an aerosol mist that seals leaks from the inside of the duct system. This inside out strategy makes it easy to access the entire duct system and all the leaks – even those hidden behind walls or other inaccessible locations.

The non-toxic aerosol sealing solution is blown into the ductwork where it remains suspended in air until the microscopic sealant particles come in contact with leaks. There the particles accumulate and bond together around the holes until they are completely filled. The majority of duct interior remains relatively free of sealant.

“It’s kind of like ‘fix-a-flat’ for the duct system,” said Randal Petrie, Petrie’s One Hour Heating and Air Conditioning, Cookville, TN. “We’ve found that in most cases, aerosealing a home or building can stop 95% of the leakage or more.”

From The Inside

The consultant brought in to test and evaluate the Marriott’s duct systems found that exhaust levels differed substantially from floor to floor. Top floors received the full 40 CFM of exhaust they were designed to pull, while bottom floors received only 5 CFM or less. He explained that like sucking water up through a straw with holes in it, the hotel’s rooftop exhaust fans were trying to evacuate air through leaky vents, and no matter how high the fan was running, it could not effectively draw air from the bottom floors. He recommended the use of the aerosol duct sealing technology to fix the problem.

Once prep work was completed, it took about an hour for the sealing team to seal all the shafts. Using his own testing equipment, the hotel’s lead engineer confirmed what the computerized sealing system indicated: average leakage was reduced from 397 CFM down to 62 CFM.

“Aerosealing the ductwork proved to be a significant aide in improving the overall ventilation of the building,” said Frank Atkins, director of engineering for the hotel. “As far as sealing leaks in the ductwork goes, we looked at several options and the aerosol approach stood out as being the most economical and non-intrusive process we found. It turned out to be the key component in eliminating our odor problem, and it will have a significant impact on reducing our energy costs as well.”

The crew working on the Hyundai building obtained similar results.

It took a couple of weeks to seal all five shafts. Leakage rates were reduced from 20% to 1.1% – well below maximum code requirements. The cost was just a fraction of the next lowest cost alternative and the work was completed in time to allow Hyundai’s new U.S. corporate headquarters to open on schedule.

“At first, fixing those leaks and getting signoff on the project meant nothing short of tearing into the newly constructed vents and starting over,” said Brian Berg, contracting engineer, Glumac, the contractors on the project. “This scenario would have the unacceptable consequence of delaying the building’s opening and running up costs. Then we learned about the aerosol approach to sealing and it literally proved to be a project saver.” 

Word about a new approach to duct sealing is quickly spreading. In the past two year, aerosol-based sealing has been used to maximize the performance of thousands of homes and commercial properties. The number of contractors offering aerosol duct sealing services has risen to over 300 worldwide, including Canada, Europe, and Saudi Arabia. Most importantly, the technology promises to have a real impact on energy savings. The D.O.E estimates that this new method of duct sealing can easily save Americans more than $25 billion a year in energy costs. 

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Neal Walsh is the Sr. Vice President of Commercial Applications for Aeroseal LLC. With more than fifteen years of experience within the building performance industry, Neal Walsh has extensive knowledge of HVAC systems, air distribution, building ventilation, indoor air quality and energy efficiency for both commercial and residential applications. Walsh holds a B.S. in Mechanical Engineering from Oregon State University and a MBA from Yale School of Management. Walsh has also held executive-level positions at Airefco Inc. and Carrier Corporation. For more information, visit

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