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Serving The Greater Fresno Area Since 1970

Serving The Greater Fresno Area Since 1970


Donald P. Dick Air Conditioning Blog

Sealing Your Ducts? So What Are You Using, Anyway?

Sealing Your Ducts? So What Are You Using, Anyway?Before sealing your ducts, you’ll need to select the right material for this important home maintenance job. It’s now possible to select an advanced duct-sealing material, ensuring a long-lasting, tightly sealed duct system. With efficient ductwork, homeowners experience improved comfort and lower energy bills. There are two basic options when it comes to choosing materials for sealing your ducts: mastic sealant and tape. Learn the pros and cons of each.


Mastic sealant is a substance used to seal ducts with a consistency like runny putty. Mastic was specifically designed with ductwork in mind, so it provides an effective seal at duct connections, adhering well to metal and fiberglass materials. However, there are two drawbacks to using mastic: It’s messy and it requires one additional step. Before applying mastic, you’ll need to fasten duct joints with sheet-metal screws. The screws hold the joints together, while the mastic prevents leaks. Because mastic is runny, it can be quite messy to work with. Take measures to protect your floors and clothing, and keep in mind that gaps larger than 1/16 of an inch should be sealed with mastic and mesh tape.


Applying specialized tape when sealing your ducts offers a measure of simplicity; however, many tapes do not offer the seal that mastic sealant does. Two tapes worth considering are oriented polypropylene (OPP) tape and foil-lined butyl duct tape. OPP’s backing offers a higher level of adhesion than cloth tape. If you choose to use it, you’ll need to first clamp the duct joints and then apply the tape. Butyl tape also offers a higher level of adhesion than cloth tape for ducts, and it remains flexible over time, a key consideration if using the tape on flexible ducts. In order for any tape products to adhere well to ducts, the surfaces must be clean prior to application.

Sealing your ducts is a job that most homeowners can do themselves. However, you may want to seek professional assistance to properly seal leaks in your ducts. In the San Joaquin Valley, contact the leading HVAC experts at Donald P. Dick Air Conditioning today.

Our goal is to help educate our customers in the greater Fresno, California area about energy and home comfort issues (specific to HVAC systems).  For more information about duct sealing and other HVAC topics, download our free Home Comfort Resource guide.

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