Special duct wrap insulation keeps ducts dry and mold-free
Save Money by Insulating Crawl Space Ducts
Crawl space insulation might not be at the forefront of your mind but forgetting about it is an expensive mistake. Uninsulated ducts that run through unconditioned spaces can lose more than 30 percent of their heating or cooling capacity. So you’ll save money by insulating them. The Residential Building Code calls for R-8 insulation for these ducts, but check with your building inspector for local code requirements. Before you insulate, however, plug any air leaks by sealing all the joints with caulk or tape.
Look for “duct wrap,” a fiberglass product with an outer foil vapor barrier. The foil barrier prevents condensation and mold from forming on the duct. And be sure to wear proper protective equipment. You’ll be handling fiberglass, so wear long sleeves, goggles, mask and leather gloves.
Unfortunately, R-8 duct wrap can be difficult to find. We checked three home centers and found only R-3 duct wrap. That didn’t meet our local codes, so we contacted a heating equipment supply house. That company knew exactly what we were looking for and had it in stock. We bought a roll of 3-in. by 48-in.-wide by 50-ft. duct wrap for our installation. We also bought a few rolls of UL181 aluminum duct tape to seal the insulation seams.
Cut to Size
Cut the ductwork insulation to match the circumference of the duct, plus 2 inches. Then peel away the foil backing and cut off 2 inches of fiberglass to create an overlapping flap for taping.
Wrap the Duct
Remove several duct hanger brackets and slide the insulation around the top of the duct. To finish the job, butt the insulation edges together along the bottom of the duct, overlap the 2-in. strip of foil, and secure it with aluminum tape.
Secure Sections with Wire
Wrap wire around the insulation to relieve stress on the seams and prevent the seam from separating. Place two wires on each 4-ft. section.
Wrap Around Ducts
Repeat the cutting, tabbing and taping procedure for each round duct.
