Insulating An Attic Ceiling
LESLIE: Dennis in Iowa is working on an insulation project. Tell us what’s going on.
DENNIS: Well, I’d like to insulate the ceiling in my attic and I was wondering if I could use maybe those 4×8 sheets of foil-back styrene.
TOM: Why would you want to do that? Are you living in your attic?
DENNIS: Yeah. I use the attic for storage and was trying to keep some of the heat out of there and I thought if I …
TOM: Yeah. Well, your attic is either going to be conditioned space or not-conditioned space. Are you heating the attic?
TOM: Alright. You don’t want to insulate the rafters, then. If your attic is properly insulated, the heat is kept at the floor level. You don’t want to add insulation to the roof structure, especially because if you do it wrong, you’re going to have an overheating situation where the shingles will wear out very, very quickly.
So you only insulate that roof rafter if you’re going to have – that attic is going to be a finished living space with heat in it. And if you do it that way, if it is finished space, then what you do is you insulate only about two-thirds of the rafter bay. So, for example, if it’s a 2×6 rafter, you’d put 2×4 insulation in that or four inches thick of insulation, so that you have space above it where air can flow and keep it cooler.
DENNIS: Oh, OK.
TOM: But you definitely don’t want to insulate it if it’s not a conditioned space, because that’s just not going to work out very well for you.
DENNIS: OK. Well, thank you.
TOM: Alright? See, now you have another project to think about this weekend, since we took that one off your list.
DENNIS: There you go.
TOM: (chuckling) (overlapping voices) Good luck.
DENNIS: (overlapping voices) Thanks.
TOM: Thanks so much for calling us at 1-888-MONEY-PIT.