06:38PM | 12/27/04
Member Since: 11/02/02
72 lifetime posts
How necessary, really, is a bathroom exhaust fan? I've just ripped my combination fan/light out, and I'm trying to decide what to do next.

I removed the existing fan largely because it was venting directly into the attic. I have serious problems with ice-dams on that quadrant of my roof. My thinking is that perhaps the fan venting warm air into that area is heating up my roof, causing the snow on that part of the roof to melt just enough to form the ice. It's a theory, anyway, and I've decided to test it by stopping the ventilation into the attic, which I've done.

I now have this 8 1/2 x 8 1/4 square hole in my bathroom ceiling. For now, I've just blocked it up so hot air doesn't escape into the attic. In the long run though, I need to either put in a light or put in another combination light+fan.

So far as I can tell, the home, built in the early 1950s, originally did not have a bathroom fan. The combination fan+light that I just removed is pretty clearly a retrofit. Thus, if no fan was necessary when the home was built, it's hard for me to comprehend why one is necessary now.

Thoughts? It'd be easier to just put in a regular light fixture. If I need a fan, then I need to somehow vent it to the outside, and that's probably a fair bit more work.

Jonathan Gennick


07:37PM | 12/27/04
Member Since: 11/27/04
174 lifetime posts
2 ways to look at it.

if you have a window then you don't need a fan. but you don't want to leave the window open in winter.

the fan venting into the attic will put condensation on the bottom of the roof sheathing and cause it to eventually drip down into the insulation. have you seen some drip lines in the insulation? but if attic is vented well then you may not notice drips.

get a good fan with a good motor and a 4 inch duct line,. insulate the duct line with sleeve insulation.. use ridged ducting if you have to go a distance sideways to go out the roof. other wise go straight up and put in a roof vent that has a flap on it to keep the cold drafts out. and insulate on top of the fan also.

ice dams...check to see that there is adequate ventilation coming up from the soffits in that area.insulation tight against the roof will cause the ice dam as there is no cold air going by, keeping the bottom of the roof cold.


05:09AM | 12/28/04
Member Since: 11/02/02
72 lifetime posts
You mentioned soffit-ventilation with respect to ice-dams. Currently, there is blown-in insulation filling the soffit area. Could that be the root of my problem? Originally, it appears to me that the soffit area was left open. The blow-in insulation was added sometime after the house was built.

Perhaps I should remove the blown-in insulation from the soffit area. When I bought the house, the building-inspector (who did home-inspections on the side) told me the blow-in stuff was cellulose treated with a fire-retardant. He said it was basically ground-up newspaper. What's the best way to remove it? The idea of scooping it out by hand from my soffits is not too appealing.

I'd really like to come to a solution for the icing problem. I get 4-6 inch thick slabs of ice that are 2+ feet wide by the length of that part of the house (maybe 12-14 feet). You do NOT want to be under it when it gives way, suddenly, from my metal roof.

Thanks, btw, for your comments on the fan. No drip-lines that I can see, at least not from moisture within the attic. I may, in fact, install a new fan/light. I found a Broan design that I rather like. I'll have to hire someone to put in the roof vent though. I don't have the equipment to work safely atop my roof.

Jonathan Gennick



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