Re-Insulating Your Attic

BILL: I have a home that has about 1,200 square feet and I want to reinsulate the attic. I’ve got about eight inches of a combination of mica, rock wool and then fiberglass that I laid in myself; total about eight inches. And with the economy the way it is and so on, I think it’s a good idea for me to bring it up to standard. It’s an older home …

TOM: Right.

BILL: … built in about 1949.

TOM: Is the insulation – Bill, is it flush with the top of the floor joist right now?

BILL: No, it’s just above it.

TOM: It’s just above it? Alright.

BILL: It’s above it about – I’d say four inches above it.

TOM: OK, and you’re not doing any storage, I presume, over it. Right?

BILL: That is correct.

TOM: OK. Well, what you want to do is probably add another six inches of unfaced fiberglass insulation. You would lay those batts perpendicular to what you have right now. And you are correct in not doing any storage there because you can’t compress it. It’s got to be nice and big and fluffy if it’s going to do its job. But if you do that between the eight inches you have, additional six – a total of 14 inches – you know that’s going to be around an r 42 or so which is a pretty well-insulated ceiling. I think you’ll see an impact based on that.

BILL: OK, now I have about a 12-inch overhang. I have a hip roof, so I have an overhang all the way around and …

TOM: (overlapping voices) Right. You want to keep the insulation so it does not compress off or choke off the ventilation. So you want to keep that back from the edge of the outer wall because you don’t want it to sort of touch the underside of the roof sheathing. You want to make sure air can get under the soffits and right up under the roof sheathing and exit through vents at the ridge.