When scheduling a duct sealing service, customers often ask how long the seal will last. Sealing duct leaks can stop conditioned air from escaping, improving comfort and efficiency. It can also prevent contaminated outdoor air from reducing indoor air quality. Below, we’ll look at the longevity of duct sealing, which can depend on the sealing material and other factors.
Duct Sealing Is Generally Not Permanent
A high-quality sealing material and effective sealing method can yield good results for many years. However, sealants tend to degrade over time. New leaks can also form as your ductwork ages or shifts.
That being said, some air duct seals can last 15 to 30 years. A seal can last for the rest of the system’s life. But with preventative maintenance, the life of a seal can be maximized. Ductwork can be resealed if necessary and additional sealants can be added if new leaks occur.
Longevity vs. Duct Sealing Material
In a study by the Lawrence Berkeley National Laboratory, various sealing methods were tested to determine how long they could potentially last. The experiments included baking tests, in which samples were placed in an oven and exposed to temperatures of about 150℉, and aging tests, in which test samples were subject to temperatures alternating between 23℉ and 203℉ and different pressures.¹
The results of these experiments provided insights into how durable certain duct sealing materials can be:
Available in different grades and tensile strengths, duct tape has a fiber-reinforced vinyl or polyethylene backing. It also has a rubber-based adhesive. While available in various colors, duct tape is usually a familiar silver or gray.
In testing, five grades of duct tape failed within seven days using the aging method, resulting in 20% to 70% leakage. Three other grades failed within 34 days using the baking method (with 30% to 80% leakage).¹
Used with rigid duct systems, foil tape features a metal foil backing and an acrylic adhesive. It is available in different thicknesses.
In aging tests, foil tape lasted anywhere from one month to three months, depending on the formulation. One type of foil tape tested via this method lasted four months.¹
Clear UL 181B Tape
Clear UL 181B tape has traditionally been applied in the factory using a thin polyester backing and an acrylic adhesive. It’s also used for ductwork assembled in the field.
In experiments, a sample of this tape lasted one month via aging testing, while others held up for three months and four months.¹
Mastic is a wet adhesive typically applied with a brush. When dry, it is a semi-rigid solid that effectively fills gaps. The adhesive is available in different consistences and can be used with mesh tape or reinforcing fibers.
In aging tests, mastic lasted for three months.¹
Butyl tape is foil-backed and includes a 0.38 to 1.3 mm butyl adhesive. The unique characteristic about it is this tape can conform to irregular shapes.
Butyl tape also lasted three months in aging tests.¹
Aerosol sealant was developed by Lawrence Berkeley National Laboratory. This sticky vinyl polymer is an alternative to other duct sealing methods and is applied to duct leaks internally.
In tests, Aerosol performed similarly to other sealants. A sample subjected to an aging test lasted three months and a sample in a baking test lasted four months.¹
A non-toxic, non-invasive method of duct sealing, Aeroseal is a material that’s blown into ductwork by a professional. It automatically coats small holes and cracks from inside ducts to minimize air loss. Otherwise, it would be difficult and time-consuming to reach and seal remote sections of ductwork.
Aeroseal provides a 10-year guarantee with its product. The company claims it has been stress-tested for up to 40 years in residential applications.²
What Type of Duct Sealing Lasts the Longest?
Various factors impact the longevity of sealants. A sealant’s physical properties and the quality of installation can affect how long it lasts, even if the initial seal is effective. An HVAC maintenance specialist can take steps to help it last longer. That’s one of many reasons we recommend annual maintenance. Air ducts can also be resealed or repaired as necessary.
Contact Sky Heating & Air Conditioning
We provide a full range of ductwork services for homeowners in the Portland area. Using our proprietary Sky Seal process, we can cut air leakage to 2% or less and also measure the results of our work. Therefore, we can guarantee the process will improve comfort, efficiency, and indoor air quality. To schedule duct sealing and other ductwork services in your home, contact us online or call (503) 694-4580.