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If UL-approved aluminum tape is applied to the return side (bottom) of air handler to filter base, is mastic still required?

Acrescue tech | Posted in Building Code Questions on

A co worker and i disagree on this mastic is required where condensation will allow tape to peel. But condensation does not occur between the filter base and air handler on an upflow system. Correct?

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  1. GBA Editor
    Martin Holladay | | #1

    AC Rescue Tech,
    Basically, you're right. Condensation is unlikely at that location.

    However, mastic is preferred over tape for longevity. The best tapes can be quite good, but the UL approval tells you nothing about tape longevity. In general, unless you are sealing a seam on an access door (a seam that needs to be opened in the future), mastic is the best product to use.

    For more information, see this article: Sealing Ducts: What’s Better, Tape or Mastic?

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