What's Causing A Musty House Smell in the Summer?
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What’s Causing A Musty House Smell in the Summer?

  • home odors
  • Transcript

    LESLIE: Brian in Arkansas is on the line and has a mysterious odor in the house. What’s going on?

    BRIAN: I’ve got a crawlspace under my house of about 1,900 square feet. And we’ve noticed, the last several years – only in the summer, when we go away for the long weekend – we come back on a Sunday night and there’s a peculiar odor in the house. It’s a musty smell, if you will, but again only in the summertime.

    TOM: Well, it’s typically more humid in the summer and you mentioned that, you know, it only happens when you’re away. So you have less air movement inside the house; doors are not being opened and closed. Is this crawlspace – under your house, does it have a vapor barrier over it, Brian?

    BRIAN: Well, when the house was built 15 years ago, they put down some probably 4- or 6-mil sheeting but it wasn’t completely encapsulated. So, what I have done, in the last two weeks, is gotten some 15-mil poly and I have totally encapsulated under the house. I’ve lapped the pillars, I’ve sealed the walls and I’ve taped the seams.

    TOM: So that’s great. So, something else that you can do is you could add an exhaust fan into that crawlspace and have it set to work off a humidistat. And the way you do that is they have crawlspace fans that are basically 8×16 inches, which is the same size as a concrete block. So in lieu of one of the vents, you install this fan in and you wire it to a humidistat, maybe mounted somewhere in the middle of the crawlspace. And then when the moisture gets really high, the humidistat will kick on the fan and it will draw some drier air through the crawlspace.

    Now, the third thing that you can do is just to be very careful with your outdoor-drainage maintenance. So by that I mean make sure you have gutters on the house, that the downspouts are discharging away from the house and that the soil around the crawlspace perimeter slopes away from the house. By trying to keep that water away from those walls, you will reduce the amount of moisture that’s building up in the crawlspace. Does that make sense?

    BRIAN: It does. I think I’ve got all that covered at this point. What about a dehumidifier? I’ve been told that’s the next step.

    TOM: You could put a dehumidifier in but I would rather see you put that simple ventilation fan hooked up to a humidistat on first. But if you want to put a dehumidifier in, I would take a look at the one by Santa Fe.

    I actually just put a Santa Fe dehumidifier in my basement and it’s working really, really well. And I liked it because it’s not very big. It hangs from the rafters and it was only 12x12x22. So it was a pretty small unit, so it didn’t take up a lot of space. And it’s doing a really good job. The one I put in takes out 70 pints of water a day.

    BRIAN: Wow. Well, as I take each step here, I’m trying to go and see if I’m doing everything correct. Could there be anything else that I’m missing or am I assuming that the smell is coming from under the house, up into the first floor?

    TOM: Well, the only other typical source of smells in houses is plumbing smells. So, sometimes you get biogas in the drains of your sinks or your tubs that can cause an odor. But if you clean those out with an oxygenated bleach, that will keep that under control.

    But if you have that kind of humid, musty smell, it may very well be coming from the crawlspace.

    BRIAN: OK. So if I totally encapsulate it and either put a fan in and/or a dehumidifier, should I see results in just a couple weeks, maybe?

    TOM: I think so, yes.

    BRIAN: OK. Because that takes care of the air under the house, which affects the first floor, as well, I guess.

    TOM: Absolutely.

    BRIAN: I will proceed with that.

    TOM: Alright, Brian. Any time you have questions, you can reach us at 1-888-MONEY-PIT.

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