DIY Duct Wrap

Insulation Round Room Ducts

• 1

  Identify the basement or crawlspace ducts to be covered. The main ducts lead from the top of the furnace along the center line of the basement. They are square and are installed below the floor joists. Individual room heat ducts are round, and lead from the main duct to the rooms. They are normally installed so that they are between floor joists.

• 2

  Cut 16-inch-wide strips of blue foam board insulation to insulate the round ducts. Also cut strips of fiberglass insulation that are the same length as the duct run.

• 3

  Slide the fiberglass insulation up into the cavity around the duct and staple it in place. The Kraft paper facing on the insulation has small paper tabs along each edge that can be stapled to the floor joist to keep it in place.

• 4

  Enclose the cavity by nailing the blue foam board over the fiberglass insulation. Nail the foam board to the floor joists using the large head roofing nails. This double insulation will prevent sound transmission and heat loss.

Insulating the Main Supply Duct

• 5

  Measure the perimeter of the main square duct, which supplies warm air throughout the house. This duct is attached to the top of the furnace, and is usually square- or rectangular-shaped aluminum that runs the length of the house.

• 6

  Cut pieces of 3.5-inch fiberglass insulation that are equal to the perimeter of the main duct plus 6 inches.

• 7

  Wrap the duct with the pieces of fiberglass insulation. Wrap each piece around the duct and then tape the ends together, so that the fiberglass insulation is wrapped around the duct like a doughnut. Position the pieces of insulation next to each other along the entire length of the square duct.

• 8

  Tape the seams between the pieces of insulation with duct tape to create a continuous insulating barrier.