What’s the Best Type of Attic Insulation?
LESLIE: Mike in Iowa needs some help with insulation. What are you working on?
MIKE: I’m interested in putting insulation in my attic. I was curious what would be better: fiberglass or blow some in.
TOM: What about foam insulation – spray foam? Have you thought about that?
TOM: So, I think spray foam is probably the best type of insulation. And essentially, the way it works is you leave the existing fiberglass at the floor level of the attic and then you spray foam between the rafters and essentially create what’s called a “non-vented attic” or an “unvented attic.” And that makes an amazing difference in the home. Of course, it’s more expensive than adding a layer of fiberglass but that’s an option.
We did that at our house last year and our cooling bill after the first summer was at 50 percent the previous year. And we’re in the middle of the first winter now and I can already see that our heating bills are not nearly what they were last year, even though our winter has been quite severe. So that’s one option.
If you want to just update the fiberglass, you can leave the existing fiberglass batts and put a second layer of unfaced fiberglass batts on top of that. Just lay them perpendicular to the original batts. And what you want to end up with is somewhere around 15 to 20 inches of insulation when you’re all done.
Now, that might be hard to fit in if you’re trying to get some storage space up there or if it gets too close to the exterior walls. So just do the best you can.
MIKE: So, the most economical, I believe, would be the blown-in stuff. Is that right?
TOM: Not necessarily. I mean that has to be done professionally or you have to rent the machine. The easiest thing to do, if you can get access to your attic, is to do it yourself with unfaced fiberglass batts.
Just remember, the most important rule for working in an attic: walk on wood.
MIKE: OK. I’ll remember that.
TOM: Good luck with that project, Mike. Thanks so much for calling us at 888-MONEY-PIT.