Bathroom Vents Dripping

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Posted by: from Calgary
2/1/2012 at 2:17:17 PM


Every time there is a cold snap in Calgary, 2 of my 3 bathroom vents leak when it starts to warms up again. The leaking has caused staining on the ceiling around my vents and it is continually getting worse. I have been up in the attic and inspected these vents and cannot seem to figure out what is causing this dripping and how I prevent it. I have felt around all 3 bathroom vents and I will explain what I discovered with each.

Vent #1: This vent does not drip from the inside but there seems to a be a "little" moisture on the outside surface of the insulation (ie. the insulation jacket) around the vent pipe. This moisture is towards the top of the pipe next to the roof but the roof is not wet.

Vent #2: This vent does drip from the inside, it is making my drywall around the vent weak and staining it yellow. I cannot find moisture anywhere around the vent. I have felt around the fan box which enters the roof, I have felt the inside of the insulation jacket (the actual insulation), and have felt the insulation jacket. There are no signs of moisture in this vent!! All I can figure is that it is coming from inside the actual vent pipe, how do I prevent this dripping?

Vent #3: This vent does drip from the inside, it is making my drywall around the vent weak and staining it yellow. The moisture in this vent seems to be from the insulation. I have cut the insulation jacket and the actual insulation is wet all the way to the roof. No moisture is on the outside (ie. insulation jacket).

The only moisture I discovered in my attic (besides what I have mentioned for vent #1) was around the hatch entering the attic. I figured out that it was not sealed properly and have since fixed this.

Please help me fix this problem. Any advise or suggestions would be great.

Thank you so much.

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Date/Time2/1/2012 at 4:26:14 PM

Hi Trevor, Nasty time to be crawling around in your attic!

There are a few things that should happen. If you have rigid ducts, each joint should be sealed with screws and foil tape. The insulation sock should then be replaced. This will ensure that none of the humid air is leaking out into the insulation. The second thing is to ensure the ducts are sealed twice at each end - the inner duct first and then the insulation sock. This will ensure the actual ducts stay as warm as possible and the humidity isn't condensing on it's way out. The third thing to check is that there should be at least a 2ft. horizontal run of duct before it turns up to the roof. This allows the air to gain some momentum before it reaches an elbow or turn. The last thing you can do is to install timers on all the fans and make sure they stay running for an additional 10 to 20 minutes after a shower and ensure all of the humidity in the rooms and ducts is vented out.

If you are feeling some moisture on the outside of the insulation jacket, it means that you probably have air leakage from your house into the attic and it is condensing on the colder duct. It could be that the fan itself has not been properly air sealed and insulated. You can also check your soffit and roof vents to ensure that you have enough and they are not blocked - the soffits and baffles can get plugged if the insulation blowers aren't careful.

Good catch on the roof hatch, air sealing is important and it should also be insulated to the same level as the attic. You can cut and glue layers of 2" pink or blue foam (each layer is R10) and build it up to R50 - the current recommended level. It should fit fairly snugly when dropping the hatch back into place.

If you aren't comfortable taking this on, you can put your requirements in the "post your project" section and get some local contractors to respond.

Good Luck with it!

Jim Kuzma

Kettleby Handyman Services

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Trevor in Calgary
Date/Time2/1/2012 at 11:31:35 PM

Thanks Jim for your response.

This is a fairly new house (5 years old) and it has the blow in insulation. I will check to see if any of the soffit's are blocked. How do I check the roof vents to see if they are blocked?

I have some additional questions. I have flexible ducts in this house, should I replace them with rigid ducts? I also do not think there a 2 feet runs before going up towards the roof, more like 1 foot or less. I want to do this work myself as I pretty much do everything myself, but I am a little concerned about unhooking the previous ducts from the top where they connect to the roof. There are 4 screws that screw into a piece of plastic, do I just remove the screws and remove the ducts and insulation jacket. I am worried I can somehow mess up the roof or cause a leak from me doing something stupid. The reason I say this is because I am unsure how it is normally connected to the roof vent. No matter what, I still have to replace the insulation sock that is wet all the way to the roof.

I also notice that there is plastic vapor barrier around the vent box in the attic. It does not seem to be perfectly sealed as some of the black sealant is loose. Could this be some of the problem?

I look forward to hearing from you again. Thanks

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Hung in Calgary
Date/Time2/6/2012 at 6:05:40 PM

Hi Trevor,

I also live in Calgary (Citadel) and experienced the exact same problem you had. My house is only 10 year old.

The problem is larger than we think. I happened to go up the artic when water was dripping from the bathroom vent. The roof sheething was totally covered with ice. And since it was warming up, ice from the sheething is melting and dripped like rain in the artic. Since the ceiling is underlayed the insulation with plastic vapour barrier, water can only run to openings in ceiling such as bathroom vents. This might be a good thing as else, the artic would developped into a pond.

This ice melting wets the insulation and overtime, lessen its thickness which effects the R-value.

I only have above 10" of insulation which is barely R-20. I'm sure it was at least R-40 when the house was built then.

The house was built with seriously under-ventilated and/or too much moiture leaks. I don't think your house and mine are isolated cases.

It's almost impossible to find all leaks now since it would require removing all insulation. Blown-in insulation makes it even less possible.

I don't know if leaks from vents are enough to ice the entire roof like what I saw.

Your house is only 5 yrs old. You might be able to go back to builder and request for warranty repair. I believe government regulation makes builders warranty all houses they built for 5 yrs.

I really like to know what they do to solve this problem.

This problem happened on every cold snap we had and this is the first time I went up the artic.

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Date/Time2/7/2012 at 1:49:43 AM

Hi Trevor and Hung, I haven't forgotten about you guys, just been pretty busy for a few days.

I am just applying a little logic to the symptoms you are describing. Warm, moist air rises. I am sure you both felt it when you opened your attic hatch. That pressure is happening all the time. There are a few ways to get visible moisture in an attic.

1) A roof leak - probably not what you have as it would be in a specific location, not widespread.

2) Inadequate attic ventilation - it is virtually impossible to seal your attic 100%. With adequate venting, any residual moisture is just carried out from the soffit to the roof vents and dissipated before it can condense.

3) Larger than normal air leaks from your house to your attic that the venting can't deal with. This is what your symptoms sound like.

I am a few thousand kilometers away and can't see what you are seeing but I have a few suggestions.

Do a search for Building Sciences Corporation and read through their information, specifically the "guides and manuals" section. It will tell you what should be happening and the best ways to make it happen.

Put your situation and requirements in the "post your project" section so you can get some local, knowledgeable contractors in to have a look.

Have an energy audit done. This should include a blower door test and might help pinpoint the source of the problems.

Ask around your neighborhood to see if anyone else is having or has had the same issues and how they dealt with them. If they haven't, you have to figure out what is different about your house.

Good Luck with it!!

Jim Kuzma

Kettleby Handyman Services

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Frank in Oakville
Date/Time4/8/2012 at 11:01:26 PM

Hi. You can have all the roof vents..and enough insulation, but if the insulation is blocking the soffits and not allowing fresh air into the attic, especially when there is a fluctuation in temperature in the winter, this may be the underlying problem. There should be baffles between the rafters attached to the underside of the roof deck. Frank

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Pat in Calgary
Date/Time5/14/2012 at 10:41:01 PM

Hi Trevor:

Black caulking is the proper sealant for sealing poly vapour barrier lap joints in Alberta. It is designed to stay flexible and sticky. Your three bath fan vents should have insulated flexible piping as you have described.

I did not read if you had a drop loop in the insulated flexible pipe. This drop loop is needed to prevent the dripping of water back through your bath fans. The reason this is needed is simple. You have warm moist air from your bathroom meeting cold air from outside and you get condensation.

The dropped loop acts like a trap for the water and if all works well the small amount of water usually evaporates.

If you have any more questions please ask.


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