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Effectiveness of Mastic Tape for Air-Sealing Ducts

bmul23 | Posted in Mechanicals on

Duct Mastic and Pregnant Wife

We’re in the process of having a ducted heat pump installed along with the associated duct work (attic and basement). The contractor and I had initially discussed using Hardcast Flex-Grip 550 mastic to seal all applicable seems. My wife is currently pregnant and after viewing the SDS I’m a bit concerned as it shows it’s category 1B for “may damage fertility or the unborn child”. The alternative is to use mastic tape (Hardcast Foil-Grip 1403) which doesn’t appear to have any of the same scary warnings as it is zero-VOC. My wife is unable to vacate during the two week install so we’re planning on using the tape instead. Will this be anywhere near as sealed?


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  1. norm_farwell | | #1

    I’ve used mastic in both forms. The stuff in the tub is easier to apply but it definitely stinks for a couple of days so I’d share your concerns. The tape should be fine. Performance will mostly depend on how conscientious the installer is, not on which product you use.

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