When can a contractor say a duct cleaning job is done? After the coils are cleaned, the blower brushed out and the dirt and debris vacuumed out? Nope.

As soon as the supply and return registers and grilles and ductwork serving them have been made hygienic? Not quite.

For a growing number of duct cleaning companies, a project isn’t finished until that newly scrubbed ductwork and its HVAC system have been sealed. Sealing ductwork involves applying products such as tapes, coatings and sprays to the ductwork’s exterior or interior to ensure homeowners and building owners get all the HVAC performance they expect.

It’s a service that’s growing in popularity, said Kristy Cohen, executive director of the National Air Duct Cleaners Association.

“We’re seeing an increase in the number of our NADCA members who are in that duct-sealing space,” Cohen said. “It’s something that they are looking at as a natural progression.”

And HVAC market suppliers are increasing their duct-sealing product offerings to meet demand. At Hardcast the company offers a variety of sealing products and equipment to help HVAC construction contractors offer the service, from the true zero-volatile organic compounds rolled mastic sealants like Foil-Grip 1404 to low-VOC water based liquid sealants such as Spray-Seal and Flex-Grip 550.

Frank Forrest, Hardcast’s efficiency solutions product manager, said his company tells contractors that offering duct sealing alongside cleaning is a smart, profitable move. If you’ve been hired to clean the ductwork, you already have cut into it to access to the interior. It’s the perfect time to talk more about indoor air quality and the various rebates and incentives that may be available for duct sealing, he said.


“It’s a really great opportunity to upsell the customer,” Forrest said.

For building owners, Forrest said contractors may want to point out that they may want to consider cleaning and sealing the ductwork that serves their existing HVAC system before spending the money on a new one. A clean, sealed system may be the only energy-efficiency boost they need.

Demand for duct sealing is also benefitting from advertising and the appearance of duct-sealing technologies on televisions shows such as PBS’ “This Old House,” according to Cohen. Viewers who watch such programs are more likely to be receptive about hearing about the products from HVAC contractors.

“It’s become much more on the radar of homeowners,” she said. “Certainly in the commercial space as well.”

While NADCA’s current standards do not encompass duct sealing, Cohen said it’s something the association is discussing and the group has held roundtable sessions on duct sealing during its annual conference. And duct sealing will be a topic at this year’s NADCA convention, scheduled for March 20-22 near Orlando, Florida.

“When our members come to annual meetings, they want to hear about ‘What are the ways for me to expand my service offerings?’” Cohen said. “It all kind of falls into this push toward energy efficiency.”

Forrest agreed, noting that Hardcast trains a lot of association members in how to use its duct sealing products.

“I think a lot of NADCA members are starting to see this as a great opportunity for them,” he said.


For some NADCA members, duct sealing is nothing new. Richard Lantz, general manager with Virginia Air Duct Cleaners in Chesapeake, Virginia, has been performing sealing for at least a decade. The company only does commercial work, and many of its clients opt to have their ducts sealed after cleaning.

Lantz said he recommends sealing for sheet metal ductwork as well as fiberglass duct board. In some cases, he insists on it.

“If you’re dealing with fiberglass duct board, we recommend not to even clean it unless you’re going to seal it,” he said.

But do customers follow the advice? In many cases — yes, Lantz said.

“When you discuss saving money, yes they do,” he said.

In some of its reports on HVAC systems and energy efficiency, the U.S. government has noted that about 20 percent of the air that moves through ductwork is typically lost to leaks. Those types of statistics are the reason that groups such as the U.S. Green Building Council have added duct sealing to their building standards, many experts point out.

Along with tax credits and other incentives for sealing, any moves to add it to national building standards or state level or local construction codes can only boost its profile and benefit the members of groups such as NADCA, they add.

“Sealing is an up-and-coming thing,” Lantz said. “The general public is not aware of the attributes of sealing and positive end result and the energy savings associated with it.”

And selling duct sealing with a duct cleaning project won’t cannibalize future business, Lantz and Forrest said. Sealing is not a substitute for duct cleaning, which should still happen on a regular schedule according to the guidelines published by NADCA.

“The sealing just improves your energy efficiency and the functionality of the system. It has nothing to do with cleanliness,” Lantz said.

When using its products, Hardcast instructs contractors to perform system cleaning before attempting to seal the system.

“We want to make sure that before you go in and do sealing that the system is clean,” Forrest said. After that, sealants can be brushed or sprayed on or rolled mastics applied.