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Bathroom Fan Back-Draft Dampers

Aston01 | Posted in General Questions on

I am looking at installing a couple of Fantech remote bathroom exhaust fans and I know they need a backdraft damper when not in use.

I’ve heard that some rattle and have other problems which made me wonder if there was a particular type that was better than the rest?

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  1. Expert Member
  2. Aston01 | | #2


    1. Expert Member
      1. doug_horgan | | #6

        I've had some not-great experiences with these outlets. They're not especially well made. The damper door tends to get stuck or fall out. The metal ductwork is attached to the plastic hood with snap closures which easily get bent out of the way, allowing the duct to detach, which allows air, insects, etc. into the duct.
        The directional nature of this type of damper seems like it would be helpful for keeping exhaust out of the soffit vents, but in my climate (Washington DC 4A) that doesn't seem to matter much, I've never seen a moisture problem related to bath venting & soffits, or even bath venting and attics. Your mileage may vary, especially in colder climates.

        1. Expert Member
          MALCOLM TAYLOR | | #7


          I'm not wild about the quality of them either, but here in the PNW non-directional venting at the soffits can not only draw moist air into the roof, but cause mold and rot on the soffit itself and adjacent cladding.

          One of the (few) benefits of soffit venting is that the duct can usually be pulled through the hole and mechanically fastened to the termination, then pushed back into place.

  3. doug_horgan | | #5

    I personally have had great luck with Fantech RSK dampers. Their springs reliably close them (as long as they're horizontal or facing up) and they leak very little air under small backpressure situations.
    I tried using cape-type dampers but low flows would not close them and we still experienced air leaking in through the bath fans. Those are quiet though. The fantech dampers click open and make a little noise on closing. But they actually work so that's what I use.

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