Crawlspace Insulation and Vapor Barrier: How to Select and Install
LESLIE: In Alabama you can find The Money Pit on WANI like Nick does. What can we help you with?
NICK: Well, I have a home that was built in the 50s. It’s hardwood with – floors. It’s got crawl space but uninsulated. And I am considering what I’m going to insulate and I just wanted to know what your guys – what you – you guys have a take on the spray foam insulation or the bat. Because I do plan on keeping this house a long time. It’s a cute little house.
LESLIE: (chuckling) Well, we’re glad you like it so much.
TOM: Well, I think that, you know, any type of insulation you put in that crawlspace is going to be a good thing. The spray foam insulation – you’re probably talking about polyisonene –
TOM: – is, you know, more expensive to do. It’s going to seal a lot better than fiberglass would. But having said that, fiberglass insulation is going to do a good job as well. I think it’s important for you to consider that in terms of heat loss only about 15 percent of the heat loss is going to be through the floor. So I think that it’s probably OK for you to save a few dollars on that floor and maybe not put the spray foam in there but simply to use eight-inch, unfaced fiberglass bats. But I would …
NICK: I used unfaced.
TOM: Unfaced. But I would also tell you to make sure that you put a vapor barrier down over the dirt floor of the crawlspace because …
NICK: That’s already there.
TOM: OK, good. Because you want to prevent humidity from coming up into the insulation because that will make it very ineffective. So this is …
LESLIE: Yeah, once the moisture affects the batting on the insulation you can really lose a huge percentage of the r value. So you want to control the moisture that’s getting to that batting.
TOM: And while you’re at it, take a look at your exterior drainage conditions and make sure your gutters are clean and free flowing and downspouts are extended well away from the foundation. And also look at the grade at the perimeter and make sure you have vents that are open.
NICK: Right. OK.
TOM: So all of those things will give you a far more efficient crawlspace and you’re going to feel it in your feet; especially in the winter.
NICK: I thank you then.