California has no intention of relaxing restrictions on the use of duct tape to seal air ducts. In a unanimous 4-0 ruling, the California Energy Commission rejected a bid by tape makers to suspend restrictions on using the tape in building homes and offices.
The restrictions were imposed after a 1998 Lawrence Berkeley National Laboratory study found the cloth-backed tape can shrivel up and fail when ducts get hot. That creates leaks that add up to millions of dollars in energy losses.
The emergency regulations forbid the use of duct tape alone to join factory built sections of flex ducting. Instead, the tape can only be used along with a sealant called mastic and collars made of steel or plastic.