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Sealing ductwork - mastic or foil tape???

I am working in my unfinished basement to seal our duct work to prevent the leakage of air from the gaps. There are a few larger gaps and many smaller. In talking to one local HVAC company, they use mastic. Another uses more tape than mastic. Code locally seems to use either foil tape OR mastic.

I have tried searching multiple places and cannot find a solid reason to use one over another. I am leaning towards foil tape since I have more experience with it. Does anyone have any advice on this?

Thank you!!!

Re: Sealing ductwork - mastic or foil tape???

With little experience with either, my gut instinct is that mastic would last longer. Though the foil tape designed for ducts is superior to other tapes, I would be afraid of the adhesive drying out eventually causing the tape to peel off. The mastic seems like it would maintain its bond with the ductwork.

Of course, I could be wrong. :eek:

Re: Sealing ductwork - mastic or foil tape???

Either properly done will work. The metal tape needs to be burnished which some installers skip, then cover over the tape with mastic to complete the seal.

Re: Sealing ductwork - mastic or foil tape???

Like was said before, either one is acceptable. Foil is easier to use, and since you have worked with foil before, go with it.

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