My house has a partially finished second floor with a larger area
of attic storage space. I have been working on improvements to the insulation in the attic storage space and have some questions.
1. Is it OK, code-wise, to use rigid foam insulation which is rated for non-exposed use in the attic storage space. I would like to use it to add insulation and better contain the F/G batt insulation which is on the walls between the finished and unfinished space. Otherwise, what rigid foam insulation should I use.
2. Some of the floor joists have 12 inch OC spacing. I have been unable to buy insulation sized for this spacing. The joists are 2×8 and are presently insulated with R-13 F/G batts. So I would like to add R-13 F/G over the existing insulation to fully insulate the joist space. Certainteed makes F/G sized this way. I called them and they sent me to H/D to special order it, but H/D didn?t have it listed in their order book. Any suggestions?
Replies
1. No...at least not in my area and I got whammied for that a couple years ago. The only fire-rated foam sheathing (that I can find), is Thermax, made by Celotex, and it is very, very expensive.
2. A. Don't go to Home Depot; go to a real lumberyard, and B. I'd recommend blowing in cellulose anyhow. Easier and less expensive to install, and probably easier for you to get a good insulating job done.
Actually, the Home Depot closest to me (probably not you, though) has batts in 24" widths that can easily be cut down the length for 12" widths. Also, most people under estimate HD and lowes ability to special order things.
I just got two 2x12 LVLs in 14' lengths from Depot and they were $55/each compare to the $68 from the traditional builder's supply house in my area.
I don't underestimate their ability.
They under perform the standards to which I have become accustomed with their competition.
Excellence is its own reward!