Basement Insulation Tips
LESLIE: Louie in Port Huron, Michigan, you are on The Money Pit. What can we do for you?
LOUIE: Yes, hi there. I have – we just bought a new house here last July.
LESLIE: Well, congratulations.
LOUIE: Thank you. And we are looking to finish the basement and I’m looking at putting insulation in between the basement and the first floor. I’d like to find out which way the face of the insulation should be directed to. And also, I guess, what’s the best way if I should put a vapor barrier over top of that?
TOM: Well, the vapor barrier goes towards the heated space. So that goes – if you’re doing from the basement up to the first floor, the paper would be up against the floor. It would not be – it’s kind of the opposite of the way that you would think. But I would recommend not using a paper-face at all. I would recommend just using raw bats; unfaced fiberglass bat insulation. You hold them up in place with – they have these wire supporters that sort of spring in between the floor joists.
TOM: And the bats are about six feet long and they’re easy to handle. They can go up in between the floor joists and you support them with these wire springs.
LESLIE: What’s the benefit of the non-vapor barrier?
TOM: Well, if you have a vapor barrier and it has any holes in it, it’s just as good as nothing. So I think that in a floor situation, you’re probably better off not putting a vapor barrier on it. Vapor barriers work really well when you can put them on and then put the drywall over it. For example, if you’re doing your walls and you put the vapor barrier against the edge of the studs and then you cover it with drywall so everything is in the right order.
TOM: But when you have the floors and the walls already completed, it’s much harder to get that kind of a seal. So what I would suggest you do is go ahead and put unfaced fiberglass bats into the floor. And you will find that it makes a nice different. It will be much, much warmer on the first floor as a result.
LOUIE: OK. Now, should that insulation be as thick as the floor joist is?
TOM: Yeah, there’s no reason to save any room there. So if you have eight-inch floor joists, use eight inches of insulation.
TOM: By the way, do you have any plans to ever finish this basement?
LOUIE: Yes, I do. That’s why I wanted to know this …
TOM: Well, if you’re going to finish the basement, remember, once you insulate that floor that none of the heat is going to leak back through it. So that means you’re going to have to have separate heat for the basement. So you’ll need to have, you know, electrical baseboard radiators are fine for a basement rec room because you don’t need to run them all that often. Or you could have your HVAC system modified to put in, for example, an additional duct down there. But once you insulate it, you are insulating – you are separating it, thermally, from the rest of the house. So you’re going to have to have a heat source for that basement once you do that.
LOUIE: Excellent. Thank you very much.
TOM: Thank you for calling us at 1-888-MONEY-PIT.