LESLIE: Hezekiah in Maryland needs a way to reduce humidity in her house. You’ve got The Money Pit. How can we help you today?
HEZEKIAH: I have a crawlspace. It’s about 4 foot high. And I had – always have this moisture problem inside the house. I mean the house fogs up, the windows fog up really bad. And after doing some research, I don’t know – I was assuming that it was my crawlspace was doing that. So I went out and bought those vapor barriers to put underneath there but I came up with this problem where I don’t know how to secure it to the wall or how far up the wall I should put it. Because I don’t really want to punch any more holes in that wall and need to reduce humidity.
TOM: Here’s the thing. There’s a lot of reasons that you may have high humidity. What I would suggest you do is to get a very thick Visqueen vapor barrier, lay it edge to edge in the crawlspace and let it overlap about 4 feet. I wouldn’t worry so much about sealing it against the wall. Yeah, it’ll make it a little bit better but I think we can – it’ll probably do an amazing job just by itself.
But you don’t want to stop there. You want to address the reason that the crawlspace is so damp and that’s outside. Typically, what happens is if the grade around the yard – especially right near the house, the first 4 to 6 feet – is flat, you’ll have a lot of water that will soak into that soil and work its way into the crawlspace.
The other thing is if your gutters are clogged or if your downspouts are not extended away from the walls – typically, downspouts will dump about a foot or two away from a foundation wall and that’s kind of silly because the water just does a U-turn and runs right back under the house. But if you were to extend those downspouts, make sure the gutters are nice and clean and regrade the soil at the perimeter so that it slopes away, all of those things will reduce humidity and the amount of moisture that gets into the crawlspace and leads to humidity in house. Because the vapor will move up through the floor structure and get in the rest of the house.
And then in the house, you could address ventilation in the attic by adding a ridge vent and a soffit vent. And that will kind of help flush it out. And essentially, you’ll have a system that will move that moisture right through.
But I wouldn’t get too hung up on how to attach that plastic to the walls. I would just lay it down as best you can, with as few seams as possible, and then improve the grading and the drainage at the foundation perimeter. And I think you’ll see a big difference just with those couple of things.
HEZEKIAH: Oh, that sounds like a better idea than I had. And I was just trying to rack my brain figuring out how to secure it to the wall and how far up the wall I should go. But I think I’d try what you said now and see if that works.
TOM: I’ll give you one other trick and that is that if it turns out you still have a lot of humidity in the crawlspace, there is a type of vent fan that’s designed to work in a crawlspace. It actually fits in the space of a typical crawlspace vent. And you can get these fans and have them hooked up to a humidistat, which is a humidity-sensing switch. And then when the humidity gets high in the crawlspace, the fan comes on and helps to pull in some dry air from the outside.
HEZEKIAH: Oh, wow.
TOM: I would do that after you do everything else we’re talking about. But that’s just one other tip that you might be able to use to reduce humidity, OK?
HEZEKIAH: Is there any specific place you can get the humidistat and that vent fan from?
TOM: Well, the vent fans, you could find them online and they come with humidistats or you can order it, OK? It’s kind of like the same kind of switch you might have for an attic fan – which I don’t recommend, by the way – but it’s humidity-based instead of temperature-based.
HEZEKIAH: Oh, OK. Alright. Thank you, thank you.
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