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Old 01-11-2009, 11:17 AM   #1
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Bathroom exhaust fan causing ice dam

Moved into my house 2 years ago (34 year old bungalow) and have experienced an ice dam during both winters we have been living there.

First noticed a leak in the bathroom, when water was dripping down through the ceiling fan. When I inspected the roof I noticed a huge chunk of ice built up in front (and under) the vent through which the same bathroom fan is vented.

Obviously the warm air blowing out of the vent is causing the dam. The vent is short and it seems like anybody (and everybody) with such a vent would potentially have the same problem. Snow falls all around the vent and when the warm bathroom air blows out of it, the snow melts and tada... an ice dam is formed (dam it) !

I'm wondering if there is a proper solution to this problem (other than removing snow with a rake or using a heated wire tape - I read that these methods can damage the roof).

Any help would be much appreciated. Thanks.


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Old 01-11-2009, 12:31 PM   #2
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wrap insulation around the vent pipe going through the roof


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Old 01-14-2009, 08:50 AM   #3
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Is the heat loss through this pipe cause enough for the water leak? Seems like it would be a very small amount of radiant heat and not sufficient to melt the ice from underneath.

Will give it a try.

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Old 01-14-2009, 04:19 PM   #4
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Well, the easiest solution would be to remove the roofing surropunding the vent, install a piece of ice barrier, re-shingle.
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Old 01-15-2009, 05:29 AM   #5
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this needs pics,seems to me ,your bathroom vent is too close to an ice dam area,check that your ceiling insulation is up to date in that area
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Old 01-30-2009, 04:35 PM   #6
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I am having a similar problem as "Arton" states. I think this is contributing to my gutter leaking in all directions as I mentioned in my post "Frozen Gutter Leak".

What I believe Arton is saying is that with the bathroom exhaust roof cap, the warm air melts the snow all around it. In my case, the roof cap is located about 1/2 way up my gabled roof. With about 8" of snow on the roof, I can see a clear path from the roof cap down to the gutter where the fan has caused the snow to melt and re-freeze. This water gets into my gutters which are filled with slush / ice / snow, and the water is leaking out from behind the gutters --- even with flashing and drip edge installed.

No other parts of my gutters have this problem except the area directly below the bathroom fan roof cap.

I, too, would like to know if there are other alternatives to the roof cap. I was thinking something like PVC pipe extending a good 2-3 feet above the roof line - similar to the stack vent - (and tall enough to always be above a given snow depth) and topped with a "breathable" cap to keep rain and animals from getting into it? Or topped with an inverted "U" shaped of PVC? This will keep the moisture out, but not sure if animals will try to crawl in.


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