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Bathroom exhaust fan leaking/snow under roof vent

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  • Jan 12th, 2010 2:15 pm
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Oct 16, 2001
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Bathroom exhaust fan leaking/snow under roof vent

OK, here goes.

Last night before we left to go out, my wife calls me to the bedroom and says there is water dripping from the bathroom exhaust fan. Not a good thing to hear of course. So I go to take the bathroom grill and a whole bunch of water comes from the grill. Basically its been acting like a cup and obviously filled over and started to drip.

Also, we have had a major cold snap and tons of blowing snow the last 2 weeks, and yesterday (the day it started dripping) it has warmed up to plus temps (about plus 1-3 degrees)

My first thought was condensation inside the pipe that was frozen because its been so cold, and then melting because its warmer now. But I also have the insulated flexible piping.

I was completely surprised at the drip, because every fall and spring I go on my roof and into my attic check the vents, shingles, etc, etc for any problems that could cause leaks, etc, etc.

So this morning I went up to look and the outside of the insulated piping was damp, and obviously followed along the pipe into the fan. I checked the insulation in the are and it didn't seem to be wet or damp. So it wasn't a roof leak.

Then I checked the piping into the roof vent, and it seems to be just stuck in there, not really mounted.

The way the winds been blowing lately, is it possible snow could of been blown up into the roof vent, and then when it warmed up just followed along the flexible pipe.

Also, we have blown in insulation, not bats.

Question 1: If thats the case, is there a proper way to mount the black insulation into the roof vent besides just stuffing it into there. Should a small metal pipe be into the roof and then the insulation pipe put over that.

Question 2: I also found some snow under neath one of the regular roof vents (the square kind, not the wind turbine ones) Is this normal? I realize snow and rain aren't supposed to be in your attic, but any roof venting must allow a little moisture (due to wind direction, etc) in because its an opening to the outside.

Question 3: How is the vapor barrier suppsoed to be against the bathroom fan. Because I had to check the insulation and the exhaust connections, I noticed the vapour barrier is just sitting against the fan box, not sealed or anything. Is it supposed to be sealed against the fan box. Right now I can basically just move the vapour barrier and look right into my bathroom.

This is only one one side of the house it seems (the north side of the roof that takes the brunt of the wind) The other side where we have another bathroom exhaust is completely dry, etc.

The house is about 9 years old. I will be going to Home Depot to ask some questions. We have been in the house for just over 2 years now, and this is the first winter this has ever happened. All the insulation is all fluffy and the spots I could check there is no moisture against the vapour barrier or drywall damage.
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20 replies
Deal Guru
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Mar 25, 2003
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Markham
Same thing happened last year
but not this year yet
I guess is depends which way wind blows and some how blew snow into the exaust vent on top of the roof
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Nov 12, 2006
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Spidey wrote:
Jan 10th, 2010 7:38 pm
Question 1: If thats the case, is there a proper way to mount the black insulation into the roof vent besides just stuffing it into there. Should a small metal pipe be into the roof and then the insulation pipe put over that.
By black insulation, I assume you mean the insulated flexible duct.
There are a couple of methods.

One uses a roof cap with a short neck, over which the duct slides.

The other, the duct (usually rigid metal) is mounted approximately flush through a hole in the roof. The gap between the duct and hole is sealed. The cap is mounted over this.
There is a sketch in the installation instructions for a Broan roof cap. Check their website.

It sounds like a combination of the 2 was used, and no sealing was done.
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Aug 2, 2001
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Spidey wrote:
Jan 10th, 2010 7:38 pm
OK, here goes.

Last night before we left to go out, my wife calls me to the bedroom and says there is water dripping from the bathroom exhaust fan. Not a good thing to hear of course. So I go to take the bathroom grill and a whole bunch of water comes from the grill. Basically its been acting like a cup and obviously filled over and started to drip.
I occasionally get dripping from my vents when I get a really big snowfall. This is because the snow covers the entire vent, and when you go to use the fan the warm air (from cooking, showers, etc...) melts the snow around the vent. The water then goes down the vent, since it's the path of least resistance.

This event makes sense to me, and seems normal with any sort of vertical ventilation (I would assume most two story homes would utilize horizontal ventilation of the first floor).
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Jan 5, 2003
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TrevorK wrote:
Jan 11th, 2010 2:50 pm
I occasionally get dripping from my vents when I get a really big snowfall. This is because the snow covers the entire vent, and when you go to use the fan the warm air (from cooking, showers, etc...) melts the snow around the vent. The water then goes down the vent, since it's the path of least resistance.

This event makes sense to me, and seems normal with any sort of vertical ventilation (I would assume most two story homes would utilize horizontal ventilation of the first floor).
Yeah, this is inevitable with bathroom venting through the roof. Make sure the insulation covers as much as it can, as warm air may condensate inside the ducting if it touches cold, which is another possibility, but it sounds more like just a lot of snow. Really nothing you can do about it, but a company called Ventilation Maximum makes a tall vent as opposed to the usual almost-flush vent, so less chance of it being buried in snow. They only sell mostly at Rona. If this is a recurring problem, sounds like it's worth the hour of labour or so in the spring to replace your vent.

If you're renovating, the best thing would be to vent horizontally out the side and with a slight angle downwards. Rain and condensation would just drip out instead of going back to the fan.
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arisk wrote:
Jan 11th, 2010 1:44 pm
By black insulation, I assume you mean the insulated flexible duct.
There are a couple of methods.

One uses a roof cap with a short neck, over which the duct slides.

The other, the duct (usually rigid metal) is mounted approximately flush through a hole in the roof. The gap between the duct and hole is sealed. The cap is mounted over this.
There is a sketch in the installation instructions for a Broan roof cap. Check their website.

It sounds like a combination of the 2 was used, and no sealing was done.
Yes thats what I meant sorry. Right now I have the roof cap like this

Image

but inside the attic i don't have a sleeve coming down, its just the hose is shoved in the roof, not secured or anything.

I'm going to Home Depot tonight. I'm thinking a small sleeve should be coming down from the roof to the insulated flexible pipe has something to go on, and then secure that with a metal band. Its secured correctly to the fan exhaust, so the bulied must of ewanted to cut corners I guess and save time

The fan hasn't dripped since Saturday, just because whatever snow was accumulated is long gone. And it never dripped last year and we had the same type of weather. But probbaly not being secured correctly it was just a matter of time before something moved due to whatever and started doing this But I will fix it correctly so this doesn't happen again. Ill bet the other bathroom fan on the other side of the roof is setup the same.

At least I dont have this setup ;-)

Image
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Ontario
Does your exhaust duct slope downwards towards the exterior? I have mine leave the fan vertical and then slope down to exit under the soffit. If there is any moisture, most/all of it will run outside.
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TrevorK wrote:
Jan 11th, 2010 2:50 pm
I occasionally get dripping from my vents when I get a really big snowfall. This is because the snow covers the entire vent, and when you go to use the fan the warm air (from cooking, showers, etc...) melts the snow around the vent. The water then goes down the vent, since it's the path of least resistance.

This event makes sense to me, and seems normal with any sort of vertical ventilation (I would assume most two story homes would utilize horizontal ventilation of the first floor).
This is the first time Ive ever had it happen in any house Ive owned. In theory Im sure theres always the chance water will get in no matter what you do, since it really is a hole in your roof, no matter how protected the hole is with vent caps and the like.
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dgmorr wrote:
Jan 11th, 2010 5:14 pm
Does your exhaust duct slope downwards towards the exterior? I have mine leave the fan vertical and then slope down to exit under the soffit. If there is any moisture, most/all of it will run outside.
nope, upwards towards the roof. Ive heard if you have exhaust fans exhaust to your soffits the moisture just flows up and cause rot underneath your eaves.

I though building codes now didnt allow venting to your soffits anymore .
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jm1 wrote:
Jan 11th, 2010 3:15 pm
Yeah, this is inevitable with bathroom venting through the roof. Make sure the insulation covers as much as it can, as warm air may condensate inside the ducting if it touches cold, which is another possibility, but it sounds more like just a lot of snow. Really nothing you can do about it, but a company called Ventilation Maximum makes a tall vent as opposed to the usual almost-flush vent, so less chance of it being buried in snow. They only sell mostly at Rona. If this is a recurring problem, sounds like it's worth the hour of labour or so in the spring to replace your vent.

If you're renovating, the best thing would be to vent horizontally out the side and with a slight angle downwards. Rain and condensation would just drip out instead of going back to the fan.
I would think that the tall vent would be worse with wind becaue they would be higher up allowing blowing snow and rain to get on there a lot worse than the shorter ones. But then again you wouldnt have the covering up problem like the short ones. So both have their advantages and disadvantages.

On houses that have the top floor venting , you dont have the option of going out the side becasudr then your just venting out the soffits, and the moisture will just float back up into the soffits causing rot there.

Our 2 basement bathrooms and dryer vent to the side, but they are closer to the ground, so the moisture can vent and float into the air, not the soffits
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Spidey wrote:
Jan 11th, 2010 5:18 pm
nope, upwards towards the roof. Ive heard if you have exhaust fans exhaust to your soffits the moisture just flows up and cause rot underneath your eaves.

I though building codes now didnt allow venting to your soffits anymore .
Yeah, my house is old for it to be coming out the soffit. If the vent is not too high up in the roof, you can still create a down slope to get rid of moisture.
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Mar 21, 2002
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Spidey wrote:
Jan 11th, 2010 5:30 pm
Our 2 basement bathrooms and dryer vent to the side, but they are closer to the ground, so the moisture can vent and float into the air, not the soffits
Ditto. My three bathrooms have ducting that joins up and runs down to the basement where the single fan is located. The exhaust then goes out the side of the basement wall with a standard flap thingy on the outside. Very simple, easy to maintain with no chance of moisture getting in. and if it did, it's just the basement so who cares.

I can understand why they vent through the roof (cheap cheap - shortest distance to the outdoors) but it is a really, really bad idea because there all all kinds of potential problems as this thread indicates.
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woof wrote:
Jan 11th, 2010 6:07 pm
Ditto. My three bathrooms have ducting that joins up and runs down to the basement where the single fan is located. The exhaust then goes out the side of the basement wall with a standard flap thingy on the outside. Very simple, easy to maintain with no chance of moisture getting in. and if it did, it's just the basement so who cares.

I can understand why they vent through the roof (cheap cheap - shortest distance to the outdoors) but it is a really, really bad idea because there all all kinds of potential problems as this thread indicates.
Is all your ducting in the wall then? When you say single fan, do you mean one fan for all your bathrooms in the basement?

Sometimes you have to do the roof way if your installing it an already finished house. I know out last 2 homes the main bathroom didnt have exhaust fans, and had to vent that way.

If I was building a house from scratch, I would do it better. But when buying already built, you kinda have to go with what you have.

Ive heard some good things about the Power roof vents. Kinda look like a flying saucer. So the bathroom fan blows and this one sucks (thats what she said)
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Dec 9, 2006
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Markham
I had the same issue yesterday... Happened around 4pm...

Took a shower and turned on the Exhaust fan.....

My wife comes into the bathroom around 5pm and there was all this brown water stains all over the sink....

What would be the issue....
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phonzy wrote:
Jan 11th, 2010 7:33 pm
I had the same issue yesterday... Happened around 4pm...

Took a shower and turned on the Exhaust fan.....

My wife comes into the bathroom around 5pm and there was all this brown water stains all over the sink....

What would be the issue....
Get up in the attic. Brown water stains could be rusty water dripping. If thats the case then that means metal has been rusted, which means it could of been wet for a long time.

Just a theory, but first thing to do is get up there and check
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