Venting a Bathroom Fan
LESLIE: Sue in Illinois is dealing with two properties that don’t mix: electricity and water.
LESLIE: How is there water dripping from your ceiling fan, Sue?
SUE: OK. We don’t know why but we had it professionally installed by an electrician. He had to go up in the attic, you know, and cut – we cut the hole and he put it in.
SUE: And every time the temperature gets below 20 degrees, water – when we turn the fan on, water condenses and comes out of there.
TOM: Oh, you have a bigger problem than your ceiling fan leaking.
LESLIE: When you say ceiling fan, do you mean an actual ceiling fan with blades or a venting fan?
SUE: No, just a – it’s a venting fan for the bathroom.
TOM: Like a – oh, for a bathroom.
SUE: It has a grate on it and it came in a housing and …
TOM: Yeah. OK. Here’s the one thing that the electrician probably didn’t do. He probably did not vent that fan to the outside.
SUE: We had another fan – our bathroom’s separate; the toilet and the stool are in like beyond the sink.
SUE: And it’s all in a little area. And there’s a fan up there in the light and he said he connected it to that type.
TOM: The water is coming from condensation.
TOM: When you have a very cold attic, you are letting warm, moist air from the house somehow up into that space. It is condensing and then dripping.
TOM: And your problem is much bigger than just water dripping out of that fan, because if you are condensing that much moisture in the attic, you potentially have sheathing damage because the underside of the plywood sheathing will – it will get wet and that can delaminate.
When was your house built?
SUE: Well, it’s just five years old. Well, six years old.
TOM: So you have – probably have plywood roof sheathing then. And you need to make sure that you have proper ventilation up there, because you’re getting a lot of condensation and that’s why it only happens when it gets to be 20 degrees outside.
SUE: OK. OK.
TOM: So, here’s what you have to do. First of all, you need to check the installation on the fan. I suspect that it’s not connected to a vent properly, OK?
SUE: OK. OK.
TOM: So that means that all the warm, moist air from the bathroom – whenever you take a shower or whatever – it gets up there and it condenses into cold water and just pours right back down again.
TOM: Secondly, you need to check your ventilation in the attic space. The best ventilation’s going to be continuous ridge and soffit vents, where the ridge vent is cut wide open and the soffit vents are cut open. Air goes in the soffits, under the roof sheathing and out the ridge.
TOM: And those two things will reduce the volume of moisture in that attic, protect the sheathing. And also, by the way, if you have that much moisture in the attic, your insulation gets very, very damp. And when it …
LESLIE: And doesn’t work.
TOM: And doesn’t work. Insulation only insulates when it’s dry, OK?
SUE: Oh, OK. OK. So we should call that electrician back and have him set that for sure.
TOM: Well, yeah. I mean at the least or just get up there and check it yourself.
SUE: Well, we’re kind of old to be doing that, so we’d have to have someone do it.
TOM: OK. Well but the thing is, if the electrician made a mistake, he’s not going to admit it. You might be better off getting somebody that’s handy just to check this.
LESLIE: Just to double-check.
SUE: OK, OK.
SUE: Yes. Thank you so much.
TOM: Alright. There you go. Mystery solved.
SUE: Alright. Thank you very much.
TOM: You’re welcome, Sue. Thanks so much for calling us at 888-MONEY-PIT.