My Duct Sealing Project
when i have a place where tape adhesive has failed and its just flopping loose not sticking or sealing the gap, ,,,
(i first try to determine that it hasn't been stretched and simply been pulled apart by receding foundation from the unit sitting on the floor and the duct suspended from the ceiling rafters. )
if it wasn't pulled apart or it it might be not then i remove any part of the failed tape that i can
if some old tape is permanently stuck , i just work with it in place
before i apply new tape, i try to prepare the surface for the adhesive by tarring or cutting a fresh piece of the tape from the roll i intend to use.
then i wad it up into a ball with the adhesive side out so its nice and sticky
then meticulously dob the tape-ball around the place i intend to stick the tape to.
if it seems like its sticking pretty good then i know i have a pretty good chance of getting it to last a little while
i have to be careful because if its a plastic membrane, it can adhere permanently and make a new problem(tare holes in something or bend sheet-metal etc..)
i may never use tape again if the urethane foam in a can hold up for and long period of time like a year.. i expect it to last 25 minimum
i didn't mention the tactics i used with the tape.. i assumed that everyone knows. but there you go.
the first time i tried tape on a duct plenum, i cleaned the surface with a suitable cleaning solvent for the conditions,(then rinse it and dry it)
after cleaning, i just stick the tape on there and assumed it was designed to adhere to most hvac surfaces.
but now, i always use what i call "the sticky tape ball" system..
also. if your foundation is receding, it can pull tape off of junctions where the unit in sitting on the floor and the plenum is suspended from the cealing... so you have to put as much excess as you can somehow.. then if it does pull off.. you might want to try keeping that tape on and try to scrunch it up into an accordion type expansion flap...
but metal tape can fatigue from vibrations so i wouldn't put much faith in that..
. but then who knows why it really failed.. it can't hurt t o do that if it seals the leaks.. i would just keep monitoring it..
i would try to develop a system to use foam forms with round ducts,, but this house is so old that i just have custom sheet metal duct work.
maybe someone will be inspired and try to develop some system's to make foam work with round ducts. 2 half circles taped together.. or a cardboard of plastic troff coil..