LESLIE: Ed in Delaware is on the line with a question about how to prevent heat loss with insulation. How can we help you today?
ED: I’ve got a house built at about 1950. It’s masonry brick and there’s about a 1-inch air gap between the inner part of the masonry and the drywall. No insulation. Obviously, I want to insulate that but I have a couple of questions around it. One would be since it’s a true masonry house, it’s not bricks over a stud frame. It’s brick.
ED: The joists rest in pockets in the brick. If I put insulation around there, am I going to have rot problems on the end of a joist?
TOM: How are you going to insulate the wall?
ED: With a low-pressure foam.
TOM: Mm-hmm. OK. Well …
ED: Or such was my thought.
ED: It’s very rough in there, so I don’t think I can do any kind of blown-in insulation.
TOM: Mm-hmm. Right, yeah. You don’t have a whole lot of space.
I’ve got to tell you, typically, believe it or not, those spaces are not insulated where you have that just very narrow space in a brick wall. And what folks typically concentrate on to prevent heat loss would be insulating the attic extra well, so to speak. I mean having 15 to 20, 25 inches of insulation in the attic is actually far more effective because that’s where most of the heat loss occurs.
To your original question, whether that will contribute to any degradation of the joists that are sitting in pockets, I doubt it. But I just don’t think you’re going to get much of a return by trying to insulate that space, because you don’t have that much cavity to insulate. And it means the amount of R-value you’re going to get in there is going to be pretty small to begin with.
ED: That’s true. Part of the issue – and I can solve this by sealing the basement and the attic, which I haven’t gotten completed yet – is that there’s literally a breeze that blows up and down there depending on the direction that the wind blows.
ED: So, at the very least, I want to close that off so I don’t get air infiltration, for example, through the few plugs that are in the outer wall.
TOM: Well, that makes sense regarding to how to prevent heat loss. I think that’s a good idea.
ED: But I was thinking, even if I can only get an inch in there, that’s an inch versus nothing.
TOM: If they’re not rotting now, I don’t think it’s going to happen when you insulate it. You’re not going to be doing anything that’s going to contribute to any moisture there. I just think that if you were to seal those drafts from below and focus on insulating in the attic the areas you can get to – I don’t feel like you’re going to get a lot of return from what’s left, which is just this very narrow space in that exterior wall that’s solid masonry, otherwise.
TOM: So why not do it in stages? Why not just do the – seal the drafts first and see what happens?
TOM: Because the hardest part of this is, obviously, getting into that wall. But if you seal the drafts and you find out that maybe you don’t have such an issue anymore, you will have saved yourself a lot of aggravation.
ED: Well, that is true, particularly since the wall is open at each joist. So I’d have to cut into the ceiling and seal that anyway, otherwise I would be insulating the floor, which does make it …
TOM: Right, exactly. That’s a lot of work, so I would hit in stages and see what the result is.