How to Insulate Ductwork
Ductwork that brings warm and cool air to the living spaces of your home may also be carrying it to places where it goes to waste, such as the attic, garage and crawl spaces. In fact, the U.S. Department of Energy estimates that poorly sealed, poorly insulated ducts can waste up to 30 percent of the energy that goes into heating and cooling your home. Ductwork is usually made of thin metal that easily conducts heat, which is why it's critical to seal and insulate it properly. Taking the time to seal and add insulation so can save you hundreds of dollars a year. Does this Spark an idea?
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Things You'll Need
- Flashlight
- Aluminum foil tape
- Duct mastic (optional)
- Brush (optional)
- Tape measure
- Utility knife
- Straight edge
Instructions
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Search for ductwork in unconditioned spaces--that is, any space not heated or cooled. Such spaces include unconditioned attics and basements, crawl spaces, garages and porches. Use a flashlight to get a good look at the ductwork so you can identify gaps or holes.
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2
Seal all joints, rivets, cracks or tears with either aluminum foil tape or duct mastic, a flexible sealant that goes on with a brush. Do not use cloth duct tape; despite its name, it's not a good choice for sealing ducts because the adhesive dries out too quickly. Allow the mastic, if applicable, to dry for 24 hours.
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Measure the surface area of your exposed ductwork, using a measuring tape.
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4
Cut pieces of duct insulation to fit your exposed ductwork and attach the pieces to the ducts. Use a sharp utility knife and a straight edge to make the cuts. The fiberglass batt goes against the duct, and the shiny aluminum foil faces out. This job goes much more quickly if you're using self-adhesive insulation.
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Seal all joints between pieces of insulation with aluminum foil tape.
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Tips & Warnings
Ductwork inside walls or ceilings between conditioned spaces generally doesn't need to be insulated, because there's minimal temperature difference between the inside and outside of the duct. So you don't need to tear open walls to insulate every inch of ductwork.
