Sealing Ducts & Air Leaks in your HomeThe air ducts -- the tubes that carry your heated and cooled air for each room - are an important part of your energy system. It is good to check your ducts for air leaks. If your ducts are easily accessible in your attic, basement, or crawlspace, you may be able to make some simple improvements. The first step is to note if the ducts have separated and if so, reconnect them. Now look for obvious holes.
Any holes should be patched. Next feel for leaks when the system fan is running, and seal any found leaks with
Mastic Duct Sealant (a gooey adhesive for sealing duct connections that dries to a soft solid) or with
Foiled Duct Sealant (a metal foil backing and an acrylic adhesive). Mastics and foil tapes should be UL-181 (others loose their bond with age). Do not use household duct tape.