Innovative Approach to Duct Sealing Turns IAQ Problems Inside Out
Thanks to innovative technologies such as aerosol-based duct sealing, solving issues and attaining optimal indoor air quality is easier now than ever before.
- By John Dixon
- Sep 01, 2015
When a decomposed body is found in Montgomery County, Ohio, it typically winds up at the Miami Valley Regional Crime Lab for autopsy. And for years, occupants of the three-story building knew whenever a new body arrived because the strong smell of the rotting corpse would permeate throughout the entire building. Oftentimes, workers in adjoining offices would just have to pack up and leave for the day until the smell dissipated.
Clearly, the crime lab building had a problem with indoor air quality (IAQ). In fact, your nose often provides the first indication that there is a problem—but even the cleanest-smelling workplace can have indoor air quality issues that lead to such symptoms as headaches, fatigue, irritated eyes, and trouble concentrating. Poor IAQ in the workplace has also been linked to longer-term effects, such as asthma and even cancer.
Given these effects, it's no surprise to find that it is costing U.S. businesses around $60 billion per year due to lost productivity, much of it attributed to poor indoor air quality.
Causes of poor IAQ can vary from workplace to workplace, but they are almost always tied somehow to the building's HVAC system. Poor ventilation, problems controlling temperature, dust, mold, high or low humidity—and, yes, even strong odors—are more often than not positively or negatively impacted by the effectiveness (or disrepair) of the heating and cooling system.
"All the air a worker breathes while in a workplace facility has first been circulated through the HVAC system," said Scott Mueller, vice president, Comfort Institute Inc. "Dust in the ductwork, a contaminated air conditioning coil, old and dirty filters, they’re all common causes of the problem."
For the Miami Valley Regional Crime Lab, the problem turned out to be one that is commonly overlooked—leaky ventilation ducts. "We had tried for years to solve the odor problem, but nothing seemed to work," said Bill Epperson, associate engineer for Montgomery County. "We spent hundreds of thousands of dollars trying different measures—installing high-efficiency exhaust fans, adding an exhaust system incinerator—we even replaced the entire HVAC system. But when a new body arrived, the entire building knew about it."
Epperson suspected that leaks in the ventilation ductwork may have been a factor, but like most buildings, the greater portion of ductwork was hidden behind the walls. Getting to the leaks and sealing them with tape or mastic would have required nothing short of a major demolition and reconstruction of the building. "Then I happened to be watching an episode of PBS's 'Ask This Old House' and saw a segment about a new duct sealing technology that worked from inside the duct to find and seal the leaks. I realized I just might have found the answer we were all looking for," he said.
Subsequent research revealed that the duct sealing technology Epperson saw demonstrated on TV was an innovation developed at Lawrence Berkeley National Laboratory with funding from EPA and the Department of Energy. Called aeroseal, it was a completely new take on the decades-old problem of leaky ducts.
"The Department of Energy understood that duct leaks were near ubiquitous among most existing buildings throughout the U.S.," said Neal Walsh, vice president of Aeroseal LLC. "They estimate that the average leakage rate hovers around 20 percent to 40 percent. This not only represented a huge energy waste, but the leaks also have a huge impact on indoor air quality. They were bent on finding a viable way to seal those leaks that was cost effective and efficient. The aeroseal technology was the answer they were searching for."
Unlike traditional duct sealing, which requires manual sealing from the outside, aeroseal technology is applied as an aerosol mist of sealant that is blown into the interior of the ductwork. Rather than coating the entire duct wall, however, the sealant particles remain suspended in air until they reach a leak. Here, they cling to the side of the hole and then to other sealant particles until the entire leak is sealed. This inside/out approach makes it easy to find, access, and seal all of the leaks, even those hidden behind walls or other inaccessible locations.
"After years of trying to solve our IAQ problem, it took just a couple of days to aeroseal the ductwork. Problem solved," Epperson said.
How Leaks Affect Indoor Air Quality
Studies show that duct leaks impact IAQ on several fronts. First, holes in ventilation shafts reduce the effectiveness of the exhaust fans working to pull air up the shaft and to the outside of the building. Like trying to suck liquid through a leaky straw, holes make the job nearly impossible.
At the same time, leaks in the return ducts will draw air from around the leaks. These may be located in dusty attic space, near chemical supplies, in bathrooms, or by other contaminated areas. The polluted air in these spaces enters the ductwork through the leaks and is then spread throughout the entire building.
At the University of Ottawa Heart Institute, where ensuring the highest level of IAQ is of paramount concern, engineers found a migrant isotope in an area of the facility far from the laboratory where it was supposed to be contained. By aerosealing the building's ventilation shafts, they were able to eliminate any concern of cross building contamination via the mechanical system.
"We were facing the possibility of having to actually replace the hospital's entire duct system. Then we heard about the aeroseal technology," said Michele Edmond, project manager at the institute. "After extensive research on the technology, our health and safety officer approved its use, and it took less than a day to effectively seal the ventilation shafts."
As engineers and facility managers come to understand the benefits afforded by proper IAQ, so does their understanding of the role that efficient ductwork—and the HVAC system in general—plays in the overall health and productivity of building occupants. And thanks to innovative technologies such as aerosol-based duct sealing, solving issues and attaining optimal indoor air quality is easier now than ever before.
The Ventilation Tissue Test
How well is your building ventilated? New York's Steven Winter Associates claims that every central exhaust ventilation system the company has ever evaluated in an existing building performs suboptimally from an indoor air quality standpoint. The American Council for an Energy-Efficient Economy (ACEEE) supports that claim with its findings that energy efficiency upgrades in multifamily buildings alone could save building owners and residents up to $3.4 billion nationwide.
So what about that office building where you work? Or the luxury hotel where you stay, or the restaurant where you regularly go out to eat? Are their ventilation systems up to snuff? Are you getting clean fresh air or sharing old, stale, potentially unhealthy air with others? You don't need fancy equipment to get a good idea—all it takes is a simple piece of tissue paper and a little tenacity on your part.
The next time you're in a public building, locate the exhaust vent (often on the ceiling or along the walls in bathrooms). Then simply place a piece of tissue paper over the vent. If the tissue sticks, consider it a pass. But if the tissue falls to the floor, you can assume that the building is under ventilated. If the exhaust rate is too low to even hold up a piece of tissue, it is certainly too low to adequately replenish the air. It's a clear indication that the building's ductwork is leaking so much air that the exhaust fans cannot adequately do their job.
This article originally appeared in the September 2015 issue of Occupational Health & Safety.