Sealing Your Ductwork? OK, So What Are You Using?

Sealing your ductwork is one of the simplest ways to improve the efficiency of your Florida home’s cooling and heating systems. But just sticking some tape on the duct joints won’t do the job. For an effective, long-lasting seal and the greatest increase in energy efficiency, it’s important to use the right type of sealing material. 

Using mastic

Mastic is a thick, gummy adhesive. Its ability to create a tight seal and stand up to temperature extremes makes it the preferred choice for most duct-sealing jobs. Look for UL 181-rated mastic, which does the best job of resisting heat. Because water-based mastic emits fewer fumes than solvent-based mastic, water-based varieties are safer for use in closed-off areas such as an attic.

Apply the mastic with a trowel, paint brush, caulking gun or gloved hands. Coat the crack or gap evenly, and spread the mastic at least 1/2 inch out from the edges of the sealed area.

Using tape

Duct tape would seem to be an easier and neater material to use. But standard duct tape — despite its name — is never appropriate for sealing ducts. Because this tape doesn’t resist temperature changes, it will quickly dry out, crack, and fall off.

If you opt for tape, choose foil-backed butyl duct tape or biaxially oriented polypropylene film with an UL 181B rating. After you apply the tape, go over it with a plastic edge, such as an old credit card, to create a strong seal. Tape isn’t a good choice for every duct-sealing job, so you might want to talk with your HVAC contractor before you use it.

No sealant holds ducts together. Metal ducts should be connected with sheet-metal screws. Before you seal gaps that are 1/4-inch wide or larger, reinforce them with fiberglass mesh drywall tape.

For more tips on sealing your ductwork or completing any other improvements for energy efficiency, contact Rinaldi’s Energy Solutions. Since 1969, we’ve been helping Orlando-area residents save energy and stay comfortable in their homes.

Our goal is to help educate our customers in Orlando, Florida and surrounding areas about energy and home comfort issues (specific to HVAC systems).  For more information about Sealing Your Ductwork and other HVAC topics, download our free Home Comfort Resource guide.

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