How to Seal Duct Work
The ductwork that conducts the air from your furnace or air conditioning system will come loose over time. The metal pieces are under a constant movement of expansion and contraction. All metal objects expand when heated. When the metal cools, it contracts. Ductwork in the home should be inspected on an annual basis to ensure that the connective joints are tightly sealed. In worst cases, the ductwork may have separated and will have to be reconnected. Keeping the ductwork sealed will also keep valuable energy dollars where they are needed the most, in your home. Does this Spark an idea?
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Things You'll Need
- Power screwdriver w/ Philips head
- Philips head sheet metal screws
- Fiberglass tape
- Scissors
- Duct mastic
- Putty knife
- Rubber gloves
- Self-adhesive foil tape
Instructions
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1
Inspect the ductwork runs, one a time. Check each connective joint to ensure the joint is still holding together. Use the power screwdriver with a Philips head to reconnect loose joints with Philips head sheet metal screws. Perform the primary inspection first and repair any broken or loose ductwork joints before attempting to seal them. You will want to ensure that all ductwork is securely supported to the framing members of the home, otherwise applying the sealant to loose joints will not be effective.
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2
Seal all joints of the ductwork with either a layer of fiberglass tape and a covering of duct mastic, or a single wrap of self-adhesive foil tape. The foil tape may break, or holes may form in large gaps of the ductwork joints. Never use "duct tape," as the adhesive will dry out and the tape will degenerate over a short period of time.
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3
Wrap a single layer of the fiberglass tape around the joint to be sealed. Cut the tape to length with scissors. Remove the tape from around the ductwork. Spread a thin layer of the ductwork mastic with a putty knife, or as directed by the manufacturer's instructions. You may have to remix the mastic if the product has been sitting for a period of time.
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4
Use rubber gloves over your hands and gently place fiberglass tape over the mastic covered joint. Begin at one end of the joint and gently push the tape into the mastic. Smooth the fiberglass tape around the ductwork joint and into the mastic material. Allow the mastic to fully cure. Consult the mastic's manufacturer directions for drying and curing times. Some mastic may need two coats to fully cover the fiberglass tape.
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5
Use the tape if you do not want to apply the fiberglass tape with the mastic, to seal the ductwork joints. Cut the foil tape to length in the same manner as described above in step 3. Peel back one edge of the paper backing on the rear of the foil approximately 2 inches. Stick the adhesive side to the ductwork joint. Work the foil tape around the duct and remove the paperback strip as you press the adhesive to the connection joint.
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Continue on to each separate joint of the ductwork to seal each connection. Larger joints may require separate pieces of tape to be applied individually.
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Tips & Warnings
Some locations of ductwork may be in confined spaces. If you feel uncomfortable entering these areas contact a certified technician to perform the work for you.
Ensure that all outdoor penetrations through the home's exterior walls are sealed as well. Even small gaps will allow large amounts of cold outdoor air into the warm interior of a home.
