Duct Sealing Solutions
A Look at Mastic and Rolled Duct Sealants
ven if your business focuses solely on duct cleaning, you’ve no doubt seen the effects of leaky ductwork: •
Poor indoor air quality (IAQ)
Inefficient and uneven heating and cooling
Higher energy costs for homeowners
In the November/December 2014 issue of DucTales, Peter Haugen, ASCS, CVI, introduced us to the basics of sealing ductwork, noting that it’s considered “the single most effective way to improve energy efficiency.” Indeed, an estimated 20-30 percent of air moving through duct systems is lost to leaks. Beyond energy efficiency, sealing ductwork is one way to help ducts stay cleaner, longer, and improve IAQ. While there are many options out there for sealing ductwork, two main players 13
are rolled mastic sealants (i.e.,foilfaced butyl tapes or butyl tape) and mastics (duct sealant).
About Duct Sealants Duct sealant is a pliable, nonhardening sealant most commonly applied by hand to seal ductwork. It may come with or without fibers, is available in white and gray and may be water- or solvent-based. They’re ideal for jobs with odd angles that may be difficult to tape, or for difficult-to-seal obstacles, like four bolt flanges. “You can force duct sealant into cracks so you have a complete seal,” says Tim Eorgan, manager of specified products at Carlisle Companies, a manufacturer of both rolled and mastic duct sealants. Duct sealants are also relatively easy to apply, and, when applied to clean ductwork, have a 100 percent adhesion. “There are no splices or seams when using a duct sealant,” says Eorgan. In addition, they’re flexible once they’ve
dried and are relatively resistant to temperature changes and humidity. Newer techniques now allow duct sealants to be sprayed on, ensuring that even hard-to-reach areas are sealed. However, duct sealants do have drawbacks. “It’s not necessarily a uniform application,” says Eorgan. “You want to apply it 20-30 mils thick, but some guys go over 40 mils.” Over application can lead to what consumers complain is sloppylooking work. While this might not matter in ductwork that’s out of sight, spaces with an industrial aesthetic and exposed ductwork can become an eyesore if duct sealant isn’t carefully applied. It can also be more time intensive, potentially driving up labor costs. In addition, duct sealant needs at least 24 hours to cure for solvent-based sealants, while waterbased sealant should be given 48 hours, depending on humidity, airflow and temperature.
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