Controlling Basement Humidity: Affordable Options
LESLIE: We’ve got Randy in Florida on the line who’s got a dehumidification question. What can we do for you?
RANDY: Our house is off-grade and the crawlspace area has ventilation all around the house. And we wanted to see about encapsulating it, you know, with the vapor-barrier plastic. And with being in Florida, I was just a little worried about humidity and possibly wanting to insulate it and see what you all’s opinion was.
TOM: Well, I do think it’s a good idea for you to add a vapor barrier to your crawlspace. That will help reduce the amount of humidity that gets into the space above the floor. And that can make the home more efficient and certainly more comfortable.
What you might also want to think about doing is adding an exhaust fan. They have fans that are basically the size of a concrete block or a foundation vent. And you could put fans on one side of the foundation and have vents open out in the other side. Then have those fans operate on a humidistat so that whenever the humidity gets really damp in that crawlspace, the fan can kick on and pull some drier air from outside across that – essentially that crawlspace floor, pulling the moisture out with it. So those two things can help you manage moisture.
On the outside of the house, you also want to make sure that if you’ve got gutters – you should have gutters on the home, and make sure that the gutter downspouts extend 6-8 feet away from that foundation. Because when you dump the additional water that collects on your roof right against that foundation, that definitely improves – increases the humidity that’s in that space.
So all of those things working together can keep it a lot drier.
RANDY: OK. So, would you be extending that vapor barrier up the walls of the crawlspace or would that interfere with that ventilation unit that you’re sticking up?
TOM: Well, you don’t want to block off the vents but yeah, I would extend it up the wall, if you could extend to 12 inches or so, just to make sure it’s sealed well.
RANDY: OK. And then would you add a dehumidifier down there or would that, essentially, be what the ventilation unit you’re talking about would do?
TOM: That’s kind of what the ventilation would do. I would not add a dehumidifier into that space. It’s not really designed for an unconditioned space like that. Dehumidifiers are not really designed for that.
RANDY: OK. And then so that would keep the humidity low enough that we could then put the batted insulation between the floor joists?
TOM: Yeah, it will keep it – it will make it lower. It’ll make it reasonably lower. It’s never going to be 100-percent dry; it’s always going to be damp. But I do think, yes, that will keep the moisture down, which is what you want to do, and allow you to get more efficiency out of the insulation.
RANDY: OK. Alright. Great. Well, thank you so much.
TOM: You’re welcome, Randy. Thanks so much for calling us at 888-MONEY-PIT.