How to Seal AC Heating Ducts
Sealing AC heating ducts is an inexpensive way to significantly lower your heating costs. Ducts that are not sealed leak air into places you are not trying to heat. This puts a strain on your heating bill because the furnace has to run longer to bring your home up to temperature. Also, air leaking out in attic spaces can cause condensation that could lead to future mold problems. It is very easy to seal AC heating ducts, and the typical homeowner can complete the task properly. Does this Spark an idea?
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Things You'll Need
- Caulk gun
- Clear silicone caulk
- Mineral spirits
- Rags
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Instructions
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Instructions
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Prep the surface of the HVAC (heating, ventilating and air conditioning) ducts for sealing. If the surface is dusty or greasy, clean it thoroughly. Mineral spirits work great for cleaning HVAC ducts and will leave a clean metal surface.
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Load up your caulk gun and caulk the duct joint connections. Fill in each with a thick bead of clear silicone caulk.
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Seal all the seams that run lengthwise on your duct. On round duct, these seams run the long way on the pipe. The seam is where the round duct "snaps" together when assembled. On square duct, these seams are on edges or where the duct "bends." You can determine which is a seam and which is just a 90-degree bend by seeing if there is a groove or folded over lap of metal. If you see these, caulk them. If you see just a bend, no caulking is necessary on that edge.
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Caulk the plenum where it connects to the furnace. The plenum is the large sheet metal duct that comes off the top of the furnace. This is a major area for air leakage on a duct system because the air pressure will be highest here due to its proximity to the blower fan.
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Tips & Warnings
If you have any screws in your duct, cover these with a bead of caulk. While each screw won't leak much air, if you have a fair number of them, the cumulative leakage can add up.
Periodically check your HVAC ducts to see if the caulk is peeling off. Repair the caulk if necessary.
Ventilate the area thoroughly when caulking. Fumes from the caulk can have harmful effects in large concentrations. Read the warning label of the caulk tube for specific guidelines.
