Too Much Moisture in Bathrooms

LESLIE: Now we’ve got Eddie in Delaware on the line who is dealing with a moisture situation going on. Tell us about it.

EDDIE: I’m having a moisture problem with two out of the three bathrooms. It’s a three-bathroom home. And each bathroom has an inline exhaust fan. And this occurred last season – last winter season – and we got a really severe winter and we’re getting a lot of condensation.

I have dampers in two of the bathrooms, at the ceiling. And last season – the last winter season – I installed an additional damper after the exhaust fan – after the inline fan in the ceiling – and I was still getting a lot of moisture, actually, at the ceiling where the sheetrock was actually falling apart. That’s how much moisture we got.

TOM: OK. First of all, right above this space, is there an attic? What’s above it?

EDDIE: Yeah. It’s an attic, yeah.

TOM: Alright. And how much insulation do you have in that attic?

EDDIE: The home is only eight years old.

TOM: So, first of all, bathrooms are sources of warm, moist air. If the temperature of the drywall is chilly, it’s going to condense and cause condensation. So you want to make sure that the attic above it, that you’ve got at least 15-20 inches of insulation between the attic and bathroom. That’s really important.

EDDIE: Oh, there is. There definitely is. And what I also did was, when I started having this problem I replaced the flexible ductwork, which was originally R6, to the maximum of R8. And I’m still getting the problem. And these two bathrooms that I’m having the problem, they are not used for showers or bathing of any sort.

TOM: The second thing I want to suggest to you is – you mentioned that you have exhaust fans in two of the three?

EDDIE: No, no. All three have their own individual, inline exhaust fans, yes.

TOM: OK. So inline – in other words, it’s ducted out somewhere? They’re all connected together and ducted out at once, at one point?

EDDIE: No, no. They’re not connected together; they’re all different.

TOM: They all vent on their own out the building?

EDDIE: Yes.

TOM: And you can confirm that the vents are working? So if you turn the fan on, you go outside, you’ll see the flapper?

EDDIE: Yes.

TOM: So, hooking them up to a humidistat/timer might not be a bad idea. Because this way, when the humidity gets high in the room it’ll automatically come on. Leviton makes such a switch, designed specifically for bath fans. And I think that might be the next step. I think we need to move more air through these rooms.

The second thing is, what’s underneath the bathrooms? Are these on the second floor or first floor? Are they over a slab?

EDDIE: It’s a ranch home.

TOM: And what’s underneath?

EDDIE: A crawlspace.

TOM: Crawlspace? OK. Does the crawlspace have a high humidity problem?

EDDIE: No.

TOM: I would recommend that you replace that existing fan switch with a humidistatically-controlled fan switch.

EDDIE: Yeah, OK. I’ll try.

TOM: Eddie, good luck with that project. Thanks so much for calling at 888-MONEY-PIT.