Lived in this home nearly three years. Last week, for the very first time, there was water coming in thru a bathroom vent after a very heavy rainfall earlier that morning.
Today I took time to suss out what’s up there, found one of these terminating both vent fans from our two bathrooms.
The fine louvers on three sides seem to be angled to make rain more likely to enter rather than be directed away, which seems counter-intuitive? It was very windy that moring during the downpour, I can imagine wind blowing rain up under the sides of this kind of vent cap unless there’s something I can’t see that extends 2″ or more above where this sits against the roof sheathing underneath.
I can’t tell what’s under the exterior housing; I can’t see how the flexible tube (spiral wire-reinforced plastic) carries the discharge from the fans to an exit that’s part of this aluminum fixture.
Is this kind of thing typically used for venting fans on a low-pitch (~3:12) roof? Maybe a local ‘handyman’ pressed a hardware store roof vent into service for something it’s not really suited for during the re-roof the year before we bought it?
Be a PITA to rework the vent discharge to vent out of the nearest soffit – if that’s even desireable – but it’s crossed my mind.
What’s ‘best practice’ for venting bathroom fans these days in a single-story residence?
Replies
That's a standard vent for like a range hood. Don't know why it wouldn't work for a bathroom fan. Have one (for a range hood) on our 4:12 roof and never had problems with it. If you look at that picture there's a sort of tube rising from the base that extends up 3-4 inches inside the unit, so water shouldn't "flood" into it unless debris blocks the flow of water below, or you get a very strong wind that is pushing a wave of water uphill.
You can certainly visit your local building supply place to see if you can find something that you think would work better. Any roofer can replace it, if you don't feel competent to do it yourself.
Iv'e seen this numerous times: a low sloped roof with a standard bathroom vent allows (under the right conditions) rain water to leak into the bathroom vent/fan unit. Winds swirl around the vent and push rain water up and into it. Common roof-mounted bathroom vents are not manufactured for installation on low pitched roofs. You could extend the top and the two sides of your roof vent with peices of aluminum, or place an L-shaped wind bafflle aprox 6" below the vent (with one leg tucked under the shingle. These fix-it methods maynot GUARANTEE a fix to the problem.
The best is to re-route the vent tube to a gable wall and install a wall-wounted vent. If that can't be done consider a soffit-mounted vent. I've used a dryer vent in such an instance. The down side is that the self-closing vent baffles with always remain in the open position, allowing cold air into the vent tube. That may not be so bad IF the fan/vent unit has a functioning baffle built into it. You can check for that by cliimbing into the attic and disconnecting the vent tube. However, this method of venting is not in strict accordance with the IRC. Sometimes, just some of the time, one must resort to less-than-ideal methods...sigh.
Mel froscarpentry.com
If indeed the low slope is the problem, there are several ways that the vent can be raised higher, without having to move it.
Thanks All!
Your replies are why I keep coming back here when I encounter something I can't explain from my experience.
DanH, can you elaborate on how that vent can be raised?
I've been considering the relocated outlet idea, there's a soffit within 8' of the farthest fan, much closer to the near one. Just a PITA given the limited attic access. I installed a Velux Sun Tube about six months after moving in, workspace is pretty tight for a guy my age.
I recall the flextube wasn't overly long or positioned to collect condensate though when it's really cold we've had a little bit of dripping from the plastic fan cover on both fans once or twice. I'm confident last weeks incursion was from the torrential rain earlier that morning.
Raising the vent would be accomplished by building a short box under it. This would need to be flashed like a chimney. Or you can possibly find a taller vent.
condensation?
Although it probably is a rain intrusion issue - I would get up in the attic and check the condition of the vinyl vent tube.
I have seen more issues with a dip in the vent pipe collecting condensation till the point it overflows back through the fan.
Idealy, the vent pipe should be insulated to eliminate condensation and even better to have been rigid pipe.
A small amount of condensation puddling may have been occuring right along with periodic use of the vent fan drying it out.
Maybe it was up to its limit and whatever rain worked its way in caused the leakage.
I have had houses where the HVAC sub ran a droopy loop of insulated flex pipe and on one of them it filled to the point of the weight pulling it loose from roof vent and dumped enough water to stain the ceiling. Not an enjoyable call from the customer.
I have since mandated rigid and insulated piping for all bath vents.
Terry
Photo
Here's the kind of vent you may want to consider.
Mel froscarpentry.com
Thanks Mel -
That looks pretty awful though I'm sure it'd work well once in place.
If for no other reason than appearance I'd go the soffit exit direction before I'd use something like that where it'd be seen easily.
Your vent is wrong for a low slope roof. go to Home Depot or any other decent building supply store and get one of these. Flash it under the shingles and make sure you have 4" insulated duct running to it.
http://www.homedepot.com/p/10-in-Goose-Neck-Vent-Roof-Cap-GNV10/100396942
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