How to Insulate an Outdoor Duct

Joey Pellham

Insulating any kind of ducting in your home is important to prevent heat loss, which can result in higher than normal heating bills. Ducting that runs outside your home requires even more insulation because it is exposed to the outside elements, such as cold weather and rain. You can insulate an outdoor duct with the proper supplies and some moderate handyman skills.

Step 1

Remove old or damaged ducting insulation with heavy duty cutting shears. Many outside ducts have the wrong kind of insulation on them and are probably not weather resistant.

Step 2

Scrape off any remaining insulation pieces, glue or tape residue with the putty knife.

Step 3

Clean the duct area with the degreser and clean rags. The new ducting insulation won't stick well unless the surface is clean.

Step 4

Install new, foil-style duct insulation, which comes in rolls that are different lengths and widths and that has a foil backing on both sides with air pockets in-between. The R-value on foil-backed duct insulation is usually 6.5 or higher, making it a good choice for outside ducting.

Step 5

Start at one end, and wrap the foil-backed duct insulation around the ducting. Use overlapping wraps as you go from one end of the duct to the next. Use metal tape to seal any seams. It has a sticky back and is specially designed for duct sealing. It tears off of the roll just like duct tape does.

Step 6

Cut any corner seams with the heavy duty cutting shears. Cut them at a 45-degree angle. Use the metal tape to close the cut seams. Overlap the coner seams a bit to make certain no leaks occur.

Step 7

Install heavy plastic sheeting over any ducts exposed more directly to rain or snow. Staple the heavy plastic sheeting to the walls and the bottom of the roof overhang.