Two ways to seal joints
1 of 2
Photo 1: Caulk
Apply a bead of silicone caulk along
both edges of the duct joint.
2 of 2
Photo 2: Tape
Seal round ducts with aluminum foil
tape, not duct tape.
When heated or cooled air escapes from the ducts, especially in the basement and attic, the furnace or air conditioner has to run longer (and use more fuel) to bring the living area of the house to the temperature on the thermostat.
Our heating expert confessed that he
never thought duct leakage was a big
issue until he saw a thermographic
image showing just how much heat is
lost at the duct joints. Today he's a
believer in duct sealing.
Sealing duct joints is a DIY project.
It's not only easy—it's cheap! Simply
buy aluminum-colored silicone caulk
and caulk every joint in rectangular
ductwork (clean the joints first with a
household spray cleaner and a rag to
remove dust). Use the caulk to seal
around the take-off boots to each
branch run. Buy high-temperature
UL181 aluminum foil tape in the duct section of a home center
and use that to seal the joints of
Never use ordinary duct tape. Despite its name, it isn't approved for
duct sealing and it doesn't hold up
well over the long term.