Bathroom vent flapper noise from wind

Discussion in 'Remodel Forum & Blog' started by Moontoad, Nov 14, 2007.

  1. Moontoad

    Moontoad New Member

    Nov 14, 2007
    I have a two-year-old home which has vent fans in the two bathroom ceilings. We live in a windy area, and the flabber doors on the fans are often banging open and shut. The noise is annoying, but I'm also concerned about the heat loss in the winter. The fans are vented out the roof through a vertical pipe connected to the fans by an insulated flexible ducting above the ceiling. I've tried weighting the flabber doors and that helps some, but I can't weight them enough to solve the problems without restricting flow during normal operation.
    So my question:
    Is there a fan model that incorporates a powered vent door that opens only when the fan is on? Or is there some other fix, perhaps something on the "chimney" that would reduce the vacuum due to wind?
  2. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    i agree. We need a better solution. Conserving indoor air instead of shooting it out through permanently open vents in the kitchen, the bathrooms and the dryer.

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  4. Hube

    Hube New Member

    Sep 1, 2004
    The noise is because the flapper is hitting on a metal to metal surface.
    The flapper should have a thin piece (1/8") of foam stripping to sit on when closed.This foam strip will stop the noise considerably.
    Either apply this thin foam strip to the flap disc or to the edge that the flapper rests on, whichever is the easiest.
  5. Moontoad

    Moontoad New Member

    Nov 14, 2007
    Thanks, Hube, but not in this case.

    I actually tried that, but the flapper (plastic) pivots in a vent (plastic pipe) and doesn't actually seat against a flat surface. Anything I came up with to pad it would prevent it from completely closing and just add to the air loss.

    I'm in Minnesota, by the way, so sucking warm air out of the bathroom on windy days is a big deal. I suppose I could just cover them up and not use them in the winter at all. Seems like surrendering to a poor design, though. I could buy new vents fans, but I couldn't be assured that I wouldn't have the same issue with new ones.

    Thanks for the suggestion.
  6. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    have you considered a louvered vent cover?

    Attached Files:

  7. Moontoad

    Moontoad New Member

    Nov 14, 2007
    Thanks, Verdeboy, but not in this case.

    The venting through the roof is VERTICAL. Sorry, I should have specified.
    Thanks for the suggestion, though.

    Anyone else? I can't believe this hasn't been encoutered and solved many times before.
  8. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Jul 24, 2007
    Robber, with some DIY on the side.
    I use one of these on my dryer:


    and I suppose you could use one of these, but I do not know how they work:


    Apparently you splice it into the vent tube and it only allows air to go one way.

    It is called a Bathroom Exhaust Fan Draft Blocker.
    Last edited: Nov 14, 2007
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    There are two flaps in my that came with the fan in-line, and I put a roof jack(?) vent in the roof that has one of it's own. The roof fixture is low and flat with a shield that only opens downslope. I bought a round to square adapter for the roof penetration, and this fit over that hole. I've not noticed any noise from it. I tend to not use it too much in the winter, but the way it is covered, it should exhaust even through a fairly big snow pile. I suppose it could get clogged, but hasn't proved to be a problem. I use it mostly in the summer when running a/c. In the winter, the added moisture quickly dissapates in the humidified house...the humidifier just doesn't run as much right after a shower.
  10. Alectrician

    Alectrician DIY Senior Member

    Jun 15, 2007
    I have the same problem on my cabin. I SHOULD have installed a different roof jack. Mine is a T top style that catches the wind.

    I took the vent cover off and propped it open cause it was driving me nuts.

    They make a jack that is more enclosed. That would likely fix your problem but would probably involve some roofing patch....unless you got one big enough to fit OVER your existing jack.

    Or you gould cut the top of the T-top off and slide the new one over and caulk it down.

    Hey...thanks. I know what I'm going to do to mine :)
  11. Moontoad

    Moontoad New Member

    Nov 14, 2007
    Good ideas all. Thank you.

    Thank you Ian, Jadnashua, and Alectrician. You all given me some ideas to explore. I really appreciate all of you taking the time to respond.

    I'm also considering toying with adding a 120V solenoid and some linkage to my existing fans to control the flapper - open only when the fan is running. Of course, I probably have to quit calling it a "flapper" then. :)
  12. Alectrician

    Alectrician DIY Senior Member

    Jun 15, 2007
    If you really wanted to go thru that effort you could probably find a electrically operated damper and place it in line with your vent duct.

    If it's 120V, normally closed, you could hook it to directly to the fan.
  13. PEW

    PEW DIY Senior Member

    Sep 2, 2004
    I have used little and weak button magnets on several bathroom fans. Contact cement one to the bottom of the flapper on the discharge side. A combination of the weight, and magnetism against the metal frame keep the flapper from banging. The fan will have no problem pushing it open.

    Just don't use a rare earth magnet, though it will keep it from banging. :)
  14. Moontoad

    Moontoad New Member

    Nov 14, 2007

    Now that is a clever idea. Thanks.
  15. kylepeavy

    kylepeavy New Member

    Mar 17, 2008
    Magnets Work Great!

    My vents are stainless so the magnets wouldn't stick to just the metal.

    But, I bought a "roll" of thin magnet at home depot, glued one on each side, and it works great. About 1" of magnet provides the right strength to keep it closed when the wind blows, but still allow it to open when the fan is on.

    Thanks for the idea!
  16. Brett Poole

    Brett Poole New Member

    Mar 7, 2015
    I too have had this same problem, and I just solved it in a deceptively simple way. When I disassembled the fan assembly, I found that when the wind is just right that the drop in pressure holds the plastic flapper open and then it "bangs" shut as the pressure changes. The flapper is molded plastic that is designed to have a neutral center of gravity about an axis that it pivots on. I expect the company (Nutone) has anticipated this type of problem, as there are plastic tabs with no apparent function on one side of the flapper. When those tabs are removed, the center of gravity changes enough to bias the flapper to the closed position. When the fan is turned on, it more than overcomes this slight bias. I can't believe all of the crazy schemes I have thought up to try to fix such a simple problem.
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