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How to Add More Insulation to a Cathedral Ceiling

  • Transcript

    LESLIE: Now we’ve got Tom in Alaska on the line who’s dealing with a roofing problem. Tell us what’s going on.

    TOM IN ALASKA: I have a rafter or a trussed – in this case, they’re 9×3½ inches – 9 inches by 3½ inches, 32 inches on center.

    TOM: Right.

    TOM IN ALASKA: Now, on top of that, I have 2×6 tongue-and-groove wood. Now, on top of that is where the insulation goes and the insulation currently is some kind of – it’s all one piece. It’s 2 inches or 2¼ of yellow foam with about 3/8-inch or ½-inch of some kind of – I don’t know. It crinkles; it can be broken off with your fingers. And then on top of that, connected to it is what looks like roofing paper?

    TOM: Right. Probably tar paper.

    TOM IN ALASKA: Right.

    TOM: So, what you’re describing is a cathedral ceiling with a sandwich-type roof structure above it. So in other words, typically in a ceiling you would have the insulation in between the rafters. Because your rafters are part of the architectural beauty of the home, the insulation is actually stacked on top of the rafters, kind of on the roof-shingle side almost.

    TOM IN ALASKA: Right.

    TOM: And that’s not unusual in that type of home. It ends up creating a bit of a deeper fascia at the front edge because of the amount of material you have there but it’s a good, sensible way to insulate that style of home. So what’s your question about this? Are you having problems with it?

    TOM IN ALASKA: I would assume that that’s only about R-19, if that.

    TOM: It can depend on what exact materials are being used. And you’re right: it’s probably not enough. And so your question might be: “How do I make that better?”

    TOM IN ALASKA: Right. And I was thinking of putting something on the inside, which I will lose the visual effect, but I thought if I put maybe a little furring strip or something on the inside, put in a blown-in, rigid foam …

    TOM: Well, if you put in blown-in, that’s going to totally mess up the appearance of those rafters. It’s hard to do that neatly. So what you might want to think about doing is adding some rigid foam insulation inside the ceiling, in between the ceiling rafters and then some other type of wood paneling over that so that when you look up, it appears that you’re looking at the underside of the roof still. You understand what I mean?

    TOM IN ALASKA: Right.

    TOM: So you can even use a tongue-and-groove thin, pine paneling that’s like 3/8- or ¼-inch thick but have that cover the insulation. And that would still give you the appearance – even if you’re losing a little bit of depth, you might be able to pick up a fair amount of additional insulation.

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