How to Insulate Ducts in an Unheated Crawl Space

Heating and air ducts are the flexible or rigid tubing that extends from the home's heating and cooling system to air registers in each room of the home. On the lower floor, the ducts often run through a crawl space. Since crawl spaces remain exposed to the outside, they cool down or warm up depending on the season. Insulating the ducts increases the efficiency of your heating and cooling systems.

Safety glasses
Dust mask
Work gloves
Long pants
Long sleeved shirt
Fiberglass batting
Utility knife or shears
Foil-backed tape

Instructions

- 1
  Wear safety gear before entering the crawl space to protect against the fiberglass particles in the insulation. Proper gear includes safety glasses, a dust mask and work gloves as well as long pants and a long sleeved shirt.
- 2
  Enter the crawl space and move to one end of the duct where it exits the floor of the home.
- 3
  Unroll a piece of foil-backed insulation batting and push it up over the duct so that the free ends hang down on either side. Pull the ends together until they meet and if there is more than two to three inches of overlap, trim the insulation to size using a utility knife or shears.
- 4
  Pull the two ends together until they meet, but don’t compress the insulation since this lowers the insulation value. Apply a long strip of foil-backed duct tape to the seam where the two edges meet to hold it in place.
- 5
  Move down the duct until you reach the next section that is not insulated. Apply more batt insulation in the same manner, but slide the end up over the first section by one inch. Seal the seam of the second section with foil-backed tape and apply another strip of tape around the seam between the first and the second sections.
- 6
  Continue installing additional insulation around the ducts until you reach the location where it re-enters the flooring.

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