Snow in through Bathroom Exhaust Vents - DIY Chatroom

RedRiver · 10-31-2009, 08:01 PM

We live in a three-year-old home in Fargo, ND. We have four bathroom exhaust fans that vent through our roof. Each of them, to some degree, "chatter" and clatter when the wind blows. Even more of a problem is that snow blows in during periods of heavy snow/wind, eventually blocking the duct and/or fan itself. This does not appear to be condensation building up on an inadequately insulated duct. The ducts appear to be properly insulated and installed. When I remove the interior fan cover, one can readily see snow packed in around the fan which ultimately melts and drips down in the bathrooms and damages the ceiling sheetrock. Is my theory of snow infiltration rationale? Does anyone have a recommended solution? Can one purchase some sort of roof vent cover that provides some resistance to opening so it isn't so easily and improperly opened by wind?

jaros bros. · 10-31-2009, 11:14 PM

You should combine all of those vents into one. The motor gets mounted up in the attic. Fantech is the company to check into. A spring loaded vent would help prevent the wind from moving the flappers so easily. The ones you have right now are not spring loaded if they're the ones I've seen before. I think they just close with gravity.

creamaster · 11-02-2009, 10:25 PM

I just installed a bathroom fan and used this same vent cap. It hasnt snowed here yet but I will update this thread if I notice any problems with mine. My cap is on the south side of the house so I am hoping I dont get any snow blown into mine. Looking at your pics I am curious why the shingles are not covering the flashing of the vents. If the caulking fails you will likely end up with water leaking in through the nail holes.

Lazy_Jake · 11-02-2009, 10:49 PM

That seems like a bad set-up for your region. You wont see that type of vent here in Maine. Vents here are done either through the underside of the overhangs (soffit) or just below the overhangs on the exterior wall.

I guarantee if you re-route the vents to the under sides of your over hangs and install sprung vents, you wont have any of these problems again.

BamBamm5144 · 11-02-2009, 10:54 PM

Yikes, who roofed that?

buletbob · 11-03-2009, 07:42 AM

That's what happens when they go to roofing classes at Home Depot. Not saying the poster did it . I see it all the time.Pure laziness. (Butcher)
They should be under the shingle. Also the first pic, looks as tho the vent is distorted. The flapper could be hung Up.

jaros bros. · 11-03-2009, 07:55 AM

They don't like to run the vents under the soffits because a lot of the moisture can easily get sucked back into the attic.

RedRiver · 11-03-2009, 07:36 PM

I appreciate the observations and suggestions. This should help as I communicate with a contractor to fix this. I'd like to fix it myself but I'm out of ideas. I replied to a ServiceMagic popup on this site and already got a local contractor to inquire.

skymaster · 11-03-2009, 08:02 PM

Whoever installed those vent caps should be taken out back and strung up with barbed wire!!!!!!!!!!!!! That is SOOOOOOOOOOOO BAAAAAAAAD
it even gives BAAAAAAAAAD a bad rap.

jogr · 11-04-2009, 03:49 PM

As the others have said the vents were installed wrong. The shingles should lap over the vent flanges so that only the lower part of the flange is visible. This lower part should lap over the shingle below but not be caulked/sealed.

I have a similar bath fan cap on my roof and it faces North. I can hear it flap a bit in high erratic winds but I've never had any snow or moisture come in. If you are seeing snow packed in the fan housing then it is clear that the flappers aren't blocking the snow. Can you remove the screw holding the mesh and see if the flappers are shutting completely?

Lazy_Jake · 11-04-2009, 07:14 PM

Quote:

Originally Posted by jaros bros.

They don't like to run the vents under the soffits because a lot of the moisture can easily get sucked back into the attic.

Interesting... I have thought about that, but was never really too concerned. I used to instal insulation in 2002 and most if not all vents I worked around went out of the soffit. I guess that the bathroom vents, AKA Fart fans, really didn't dispel a whole lot of water vapor to make it too much of a concern. Where do vents now 'days vent out to, other then the roof top?

creamaster · 11-04-2009, 08:56 PM

Quote:

Originally Posted by Lazy_Jake

Interesting... I have thought about that, but was never really too concerned. I used to instal insulation in 2002 and most if not all vents I worked around went out of the soffit. I guess that the bathroom vents, AKA Fart fans, really didn't dispel a whole lot of water vapor to make it too much of a concern. Where do vents now 'days vent out to, other then the roof top?

I saw a Ask This Old House show where they vented the bathroom fan out the sidewall of the house from the attic, the duct run wasn't too far because the wall was right there.

RedRiver · 11-11-2009, 11:52 PM

I returned to the roof today. I removed the screens and "flapper" from each of three exhaust fittings on the roof. They seemed to be functioning properly. With the help of my wife, we turned on each fan individually to observe flapper response on the roof. Two of the three appear to be working just fine.

The third one was not functioning.

It appeared that there was no air exiting the roof vent despite an apparently well-functioning fan in the bathroom. There was moisture condensation evident inside this roof vent. By sticking my head up through the attic access, this fan's duct takes a long route to the exhaust vent with several dips and valleys along the way. Could it be that I have a duct filled with enough water to totally obstruct the flow of exhaust?

creamaster · 11-12-2009, 07:33 AM

Try and see if the fan will hold a piece of toilet paper against the grill via suction or if its too high try some smoke and see if the smoke gets sucked through, if both either of these fail then you likely have an air flow restriction. If either pass the test then try to check the duct attatchment at the fan, it may have come off and you might be just venting into the attic.

oh'mike · 11-12-2009, 08:33 AM

Your duct is probably full of water. I've seen that many times with roof vents.

Between moisture condensing in the exposed uninsulated vent tube and the snow blowing in--
Waters going to run down hill--That's why bath vents are often vented through the soffit or wall in cold areas.

Good luck on that---MIKE---