New Technology and Solutions
Cleaning or sealing your ductwork can be much easier on your wallet than upgrades.
“Some in the industry have suggested that duct leakage above 15% indicates sealing will be cost-effective,” Liescheidt explains. “There are very good products on the market that make the first cost more attractive.”
A development in sealing duct leakage in commercial buildings involves sealing leaks from the inside out. “This aerosol-based sealing technology works by pressurizing a duct system with a fog of sealant particles,” writes ASHRAE member Mark P. Modera, director of the UC-Davis Western Cooling Efficiency Center. “By temporarily blocking the diffusers, the sealant-laden air is forced to the leaks.”
Carlisle HVAC has developed robotics to inspect, clean, and seal ducts from the inside. Its robot visually detects leaks by recording video on an SD card, which also allows you to verify problems and results as opposed to taking a contractor’s word for it. It cleans with a brush and vacuum and seals using a rubber-like substance and spray nozzle.
There are currently 20 projects using the robot, Forrest says. One contractor estimates the charge to inspect, clean, and seal the ductwork of a 100,000-square-foot building at $1.50 per square foot.
The cost can be worth it though. Tighter ducts can have an attractive payback, Liescheidt says.
When design engineers calculate CFM, their equation typically accounts for duct leakage as a given. This doesn’t have to be the case, Forrest says, adding that ductwork should be like plumbing. Zero leaks are doable, he explains, but 2.5% leakage is very feasible.
“The Lawrence Berkeley lab determined that if you get your leakage down from 10% to 2.5%, it would have a 30-33% impact on your energy bill,” says Forrest. “The savings are very significant.”
Chris Curtland (firstname.lastname@example.org)
is assistant editor of BUILDINGS.