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Venting my bathroom out of a cold attic

I have a bathroom vent that vents up to the attic. I also have a wood shingle roof so my attic has vents at each side of my attic keeping air moving up and through the attic so it stays pretty cold up there above my insulation. I live in Montana and it gets very cold. So today I noticed a leak in my ceiling. I thought at first it was melting snow. When I got up in my attic it ended up being a large chunk of ice that was melting inside my vent tube. Apparently the vent tube is getting so cold that the water vapor wasn't making it out of the house before condensing to water and settling in the tube. Have you heard of this happening and what can I do to fix this. I am wondering if exhausting directly into my attic is going to ruin my roof if the vent isn't working at getting the air out of the house before it condenses. Please help me. Brett Veltri

Re: Venting my bathroom out of a cold attic

1. Venting into an attic in your area (cold climate) is not a good idea.

2. You must vent to the outside, and through the side of the house (as apposed to the roof).

3. Insulating the metal vent will help.

Re: Venting my bathroom out of a cold attic

It's fine to vent other than to a side of a house just so long as the humid vented air doesn't re-enter the attic before the moisture dissipates. Venting through a soffit is common, but a bad idea if the whole soffit vents to the attic causing the moist air to go right back up and in!

Newest codes require bathroom vents to be at least 3' away from any entry point for attic ventilation. If you have enough soffit venting otherwise, you can use solid soffit or block the venting holes from the inside beside the bathroom vent. Insulate the vent and the ducting (or use insulated flex duct piping) and that should cure the water re-entry problem.


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