Insulate Your Duct Work

Save 20-30% on Heating and Cooling Bills with this Easy ‘Sweat-Equity’ Project

Your home’s duct system carries the air from your furnace and central air conditioner or heat pump to each room. These ducts are typically made of sheet metal, fiber glass, or other materials that easily conduct heat. Ducts are also usually located in unconditioned spaces and unfortunately, many duct systems are poorly insulated, or not insulated at all.

  • 10 – 30 % of the energy used to heat and cool the air in your home is lost to conduction through duct surfaces.
  • Poorly insulated ductwork results in hard to maintain temperatures in rooms served by long duct runs and can add hundreds of dollars a year to your heating and cooling expenses.

Start by downloading the instructions & materials list (pdf) and then watch this four-part instructional video series.

Instructional Videos

Part 1: Insulate Ductwork

Part 2: Supply Ducts

Part 3: Transition Ducts

Part 4: Hot Water Pipes


Three Easy Steps to Enjoy the Benefits of Insulated Ductwork

  1. Start by cutting the polyisocyanurate sheathing to wrap around the supply and return trunks’ sides and bottoms. Tape the cut pieces of sheathing to the trunks and adjacent sheathing using the foil faced duct tape.
  2. Wrap the 6 inch round distribution ducts with fiberglass batts. Keep in place using staples and string. Zigzag the string back and forth across the length of the fiberglass insulation batt and staple it to the joists or underside of the floor. Wrap or stuff fiberglass insulation around the sheet metal “boot” that connects the 6 inch pipe to the register.
  3. Cut the fiberglass batts to size and place on top of the supply trunks, between the floor joists.


ENERGY STAR® suggests these benefits for insulating your ductwork.

  • Improve Comfort: Duct insulation minimizes conductive heat losses and gains, allowing supply air to be delivered closer to desired temperatures. In winter, leaks of heated air will be reduced in rooms supplied with long duct runs. This can result in quicker recovery from night-time setbacks and a more consistent level of comfort throughout a house.
  • Save Money: The average homeowner spends over $600 per year on heating and cooling. Leaky ducts can reduce heating and cooling system efficiency by as much as 20 percent. Sealing and insulating ducts increases efficiency, lowers your energy bills, and can often pay for itself in energy savings.
  • Protect the Environment: Energy used in our homes often comes from the burning of fossil fuels at power plants, which contributes to smog, acid rain, and global warming. Simply put, the less energy we use in our homes, the less air pollution we generate. By sealing your ducts and reducing the amount of energy necessary to comfortably heat or cool your home, you can reduce the amount of air pollution generated.
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