Author Topic: Leaks around static roof vent  (Read 490 times)

less4success

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Leaks around static roof vent
« on: January 06, 2022, 01:33:38 PM »
I'm looking for ideas on how water is getting in through my roof (near a roof vent). Unfortunately, the attic is only about 10" tall at the point, so I haven't so far been able to get a good look (I've been relying on a camera on a pole). At least the attic access is close!

My best ideas:
  • Water (or snow) splashing (or piling up) and getting in through vent (which has no "lid", just an aluminum screen) -- is this possible? How to prevent?
  • Leaking around roof vent fasteners -- unlikely since I replaced the vent and the fastener/cement are pretty new and I haven't seen water around the fastener
  • Condensation from the exhaust fan dripping within the attic -- is this possible? I would hope not because I'm not sure what I could do about it!
  • Condensation from somewhere else in the attic -- hopefully not likely since I'd probably be getting mold -- I will be up in the attic soon to double-check

Only the first one seems plausible to me, but I (so far) haven't been able to catch any water getting in "in the act" (e.g. during a storm). Are there other common causes of leaks around (fairly new) roof vents? Most info I found was for old or improperly installed vents.

More details, in case they're helpful:

This is all happening in a bathroom. There is a bathroom exhaust fan in the middle of the room and a light fixture a few feet toward the side of the house (directly down the pitch of the roof from the vent). Water is getting into the light fixture. I'm seeing maybe 1 - 2 tbsp of water in the fixture, maybe once or twice a year (presumably during storms, although I haven't witnessed it--also could be related to recent snowfall, which is uncommon where I live).

The exhaust fan connects to a steel tube that has two 90 degree turns and then goes up and ends at a hole in the roof. At the hole in the roof, there's a static roof vent that looks like this one from Home Depot. There are no other vents in this path from the top of the roof (and I've never seen water "up pitch" from here). Edit: the tube is NOT connected to the roof vent in any way, is this normal?

I actually replaced the roof vent a few years ago because the old one (installed by a roofing company!) wasn't installed correctly (they drove fasteners through the part of the vent that explicitly says not to do that. Prior to my fix, there was a significant (and visible) amount of water getting in during storms, but I haven't witnessed any water (even during storms) get in since I replaced the vent (but I know it's still happening sometimes because water collects in the light fixture). The vent is tucked under shingles and sealed with roofing cement, per the installation instructions. As far as I'm aware, water could splash up and into the roof vent, but that doesn't seem like it would lead to the amount of water I'm seeing (although I'm just guessing).

One other observation is that the hole in the roof is much larger than the exhaust pipe. I thought for a bathroom exhaust, you usually cut a circular hole that is the size of the pipe, but (for whatever reason) the hole is 1 - 2" bigger in diameter than the exhaust tube. It's still smaller than the 8x10" rectangle this static roof suggests, so I don't see why this would be a problem. Edit to clarify: the exhaust tube is NOT connected to the roof vent. It just sort of ends at the point where the roofing would be. I don't see a particular problem with this, but it wasn't what I (as an uninformed person) would have expected.
« Last Edit: January 06, 2022, 01:58:46 PM by less4success »

lthenderson

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Re: Leaks around static roof vent
« Reply #1 on: January 06, 2022, 03:26:58 PM »
maybe 1 - 2 tbsp of water in the fixture, maybe once or twice a year

Small leaks like this are impossible to armchair quarterback and diagnose properly but for that amount of water, I would start my search around the bathroom exhaust fan. Is it insulated? If not, it might be condensing in the vent pipe and running back down towards the bathroom. More likely is that the warm moist bathroom air in condensing on the underneath side of the static vent and dripping back down into the light fixture. I'm assuming you already know that terminating a bathroom vent in the vicinity of a static roof vent is a big no-no for this very reason.

less4success

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Re: Leaks around static roof vent
« Reply #2 on: January 06, 2022, 04:33:18 PM »
Thanks! I did not know that (and apparently neither did the roofing company the previous owner hired). Let me think about that more.

Also, I went into the attic (and itís even more cramped than I rememberedómaybe 6Ē of clearance), but this time I do see moisture starting at the vent.

I wonder if the condensation would occur on a cold but not rainy day (to distinguish rain getting in from condensation).

Edit: thought about this more, and I think your explanation is the most plausible. It sounds like exhaust vents should have a drain path for condensate, but the roof vent I have (same one as originally installed, minus the holes they put in the original) is just open (with an aluminum screen). Thereís nothing to stop condensation from running down the sides, and even worse, since the connection is just open, water can run into the attic itself instead of just down the exhaust duct.

I probably wasnít seeing this problem often because we rarely used this bathroom until the last 6 months or so. Iíll see if I can get it dry and then try and recreate the problem on a cold but not rainy day.

Iíll probably need a contractor to actually repair this mess, but at least now I have something to watch for. Thanks again!
« Last Edit: January 06, 2022, 06:06:23 PM by less4success »

sonofsven

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Re: Leaks around static roof vent
« Reply #3 on: January 06, 2022, 06:27:25 PM »
I won't speculate on condensation issues, but if the roof vent is actually leaking, I see three primary reasons why.

Incorrect installation, or incorrect location, or incorrect product.

Since we already know it's the incorrect product, I would start there and get a vent that allows for a positive connection to the vent pipe, install it carefully, tucking under at the top and sides and over the bottom course, and monitor it.



less4success

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Re: Leaks around static roof vent
« Reply #4 on: January 06, 2022, 07:19:46 PM »
Good suggestion. If I replace the vent with a proper exhaust vent, I need to make sure there's still adequate attic ventilation (since I'll be basically removing/repurposing one of the existing vents), correct?

Unrelated: I've also been putting some thought into why this was done originally. My best theory is that (when the roof was redone, back in 2017) they decided to use a series of static roof vents, numbered and spaced appropriately, but then when they got to hooking up the bathroom vents, they tried to take a shortcut and run the duct to the (very nearby) existing vent (it's not even a straight shot, so I doubt the vent was installed specifically for this exhaust fan).

sonofsven

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Re: Leaks around static roof vent
« Reply #5 on: January 07, 2022, 09:25:33 AM »
Good suggestion. If I replace the vent with a proper exhaust vent, I need to make sure there's still adequate attic ventilation (since I'll be basically removing/repurposing one of the existing vents), correct?

Unrelated: I've also been putting some thought into why this was done originally. My best theory is that (when the roof was redone, back in 2017) they decided to use a series of static roof vents, numbered and spaced appropriately, but then when they got to hooking up the bathroom vents, they tried to take a shortcut and run the duct to the (very nearby) existing vent (it's not even a straight shot, so I doubt the vent was installed specifically for this exhaust fan).

In that case I would install a new vent just for the exhaust fan in a new location, as close as feasible to the fan to keep the duct run short.

index

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Re: Leaks around static roof vent
« Reply #6 on: January 07, 2022, 09:58:40 AM »
Good suggestion. If I replace the vent with a proper exhaust vent, I need to make sure there's still adequate attic ventilation (since I'll be basically removing/repurposing one of the existing vents), correct?

Unrelated: I've also been putting some thought into why this was done originally. My best theory is that (when the roof was redone, back in 2017) they decided to use a series of static roof vents, numbered and spaced appropriately, but then when they got to hooking up the bathroom vents, they tried to take a shortcut and run the duct to the (very nearby) existing vent (it's not even a straight shot, so I doubt the vent was installed specifically for this exhaust fan).

In that case I would install a new vent just for the exhaust fan in a new location, as close as feasible to the fan to keep the duct run short.

This is the correct course of action. Buy and install something like this:

https://www.supplyhouse.com/Broan-636-Model-636-Steel-Roof-Cap-for-3-or-4-Round-Duct-Black-Finish

I would guess the bathroom vent may have been installed incorrectly before the roofing company got there. Electricians usually install bathroom vent fans, and won't install a roof vent due to insurance considerations. The electrician probably installed the vent incorrectly (as a temporary measure) and told the homeowner to call a roof company to install a new vent which never happened.

sonofsven

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Re: Leaks around static roof vent
« Reply #7 on: January 07, 2022, 10:05:43 AM »
Generally, HVAC is responsible for moving air.

less4success

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Re: Leaks around static roof vent
« Reply #8 on: January 09, 2022, 10:37:06 AM »
Update: still trying to pinpoint the problem; waiting on the weather to change again.

I did an experiment today. It was fairly cold (< 40F), with high humidity (97%), but not raining. I looked in the attic and saw no water. Then I turned on the shower to hot and let it run (with the bath fan going) for 10 minutes (until the mirror was very steamy), then let the fan run for maybe 20 more minutes (clearing up the mirror). I looked in the attic again (hoping to catch some condensation dripping back in), but there was still no water. (Also checked again later with the same result.)

So the good news is that the fan isn't causing tons of condensation to fall into the attic (like I had feared), but that means I still don't know how water is getting in. I also checked on the roof again, and it looks like this vent was installed specifically for the exhaust fan (instead of just being a generic vent--all the other static roof vents are in a straight line and this one is not part of that line). That's good because I can replace the vent without affecting general attic ventilation (a concern I had raised in a previous post).

Next steps: repeat the experiment on a day when it's colder, and also on a day when it's raining (but ideally not windy). Hopefully that will narrow down the cause.

Obviously, I still should replace the vent with the proper kind (with a damper, etc.), but I'd like to be able to recreate/pinpoint the problem first, in case the vent type isn't the primary problem.
« Last Edit: January 09, 2022, 10:39:11 AM by less4success »