Bathroom vent flapper noise from wind

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Moontoad

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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?
 

Hube

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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.
 

Moontoad

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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.
 

Verdeboy

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have you considered a louvered vent cover?

Louvered vent cover.jpg
 
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Moontoad

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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.
 

Ian Gills

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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.
 
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Jadnashua

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There are two flaps in my system...one 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.
 

Alectrician

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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 :)
 

Moontoad

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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. :)
 

Alectrician

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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.
 

PEW

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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. :)
 

kylepeavy

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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!
 

Brett Poole

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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.
 

Scholeyhome

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Picture is worth a thousand words - here are some images of our NuTone model with plastic flapper. Gusts of wind slam the exposed bit against the pin keeping us up at night. See the red arrow I added to the photo. As next step, I am looking to adhere sound dampening piece to that 'pin' that I poi
nted to with the arrow to kill the sound...maybe using the magnet idea too mentioned above. Did not see the plastic tabs mentioned by Brett. Images from HD site.


IMG_3744.jpg
IMG_3743.jpg
IMG_3741.jpg
 

Loungeact

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I have the Nutone LS80LF bathroom vent fan. After an easy removal of the fan to access the plastic flapper, I simply used double sided 3M tape and attached a plastic washer at the bottom of the flapper. Worked PERFECTLY. Now it opens when it's turned on and makes ZERO flapping noise when it's not. Hope that helps!
 

Sabre786

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I have the Nutone LS80LF bathroom vent fan. After an easy removal of the fan to access the plastic flapper, I simply used double sided 3M tape and attached a plastic washer at the bottom of the flapper. Worked PERFECTLY. Now it opens when it's turned on and makes ZERO flapping noise when it's not. Hope that helps!


Isn't the flapper on the outer side of the ceiling? Is it accessible from inside the bathroom?
 
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