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Community and Q&A

Bathroom exhaust fan damper

carlosdanger | Posted in Energy Efficiency and Durability on

I was just installing a Panasonic whisper green select exhaust fan. I’ve heard that Panasonic makes quality fans and I liked the options that the fan has, but I was unimpressed with the damper. Its flimsy plastic and it doesn’t seal the fan at all. I can clearly see through the fan and down to the floor through two big gaps on each side of the damper. I remember the last fan I installed was a cheaper brand but it had a nice metal damper that seemed to seal quite well. Is there anything that I can do to seal the fan better? Would installing a duct damper be wise. Thanks for any help.

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  1. exeric | | #1

    I think you're onto something important. Many of the included dampers in various devices are deficient. A good idea would be to install an aftermarket in duct damper. You didn't say whether it was a horizontal run to a wall vent or vertical run to roof vent. The reason it is important, besides the orientation of the damper, is that the gravity assisted vertical runs need less spring assistance to close if its not a cape damper. Cape dampers use very light fabrics and don't involve springs.

    Whichever you select, flap or cape, use two of them in series so you have a dead air space between them that acts like an insulator. Preferably the section between the dampers should be in conditioned space, i.e., within the insulation depth if its standard insulation over a ceiling in an unconditioned attic.

    Finally, make sure you seal the area around the circumference of each damper so air cannot bypass the dampers. They don't always fit that tight in ducts. Then remove any dampers that came with the original fan and also any roof flap that comes with that vent.

    Last, but definitely not least if you use the spring assisted dampers in a vertical orientation: make sure there is not too much back pressure from the springs to stop the flaps from opening fully. If there is then just cut some of the "legs" on one or more of the closing springs of either or both so that both dampers open fully with the fan on.

  2. carlosdanger | | #2

    Thanks. I'm going to install two flap dampers in the way that you described. I am venting to the outside wall and my ducting is within the insulation depth. One thing I wasn't clear on - you are saying that I should remove the damper included with the exhaust vent on the outside of the house? I was thinking that I might leave that one on just to keep out birds, etc. Thank you very much for your response.

  3. BillDietze | | #3

    There are several existing answers to the question. Search this website for "cape damper" and you'll find several of them.

  4. exeric | | #4

    Kevin, sure, keep the flapper on the wall cap if it doesn't mess with the air flow and serves a useful purpose. There isn't much air flow in those Panasonic's in the "ventilation mode" so that's why you have to be careful to make sure the dampers still open enough.

  5. carlosdanger | | #5

    Thanks again. I wound up ordering a more traditional style damper by fanco because it got very high ratings. Amazon reviews for the Cape dampers weren't that good although it sounds like people on this site may have had better luck with them perhaps. Anyway, hopefully what I ordered will provide a better seal than what I have now. Thanks again

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