What is the correct name for Foam Insulation Boards?

[John6012]

I am going to cut nailers tomorrow and need the correct name for the foam insulation board for the correct cut. I've searched HD and cannot pull up the boards. I need 7/8 foam but I'm not sure they have this size. I found 4x8x1/8 oak door skins for 8.00 and that's what I'm going to use on the ceiling and int sides. I'll check back in the AM before I go to the garage. Thanks

[IraRat]

You mean insulation, right? It's called rigid foam insulation, and I don't think you'll find it in 7/8.

Certain things you just can't find on Lowes and HD's web sites, unless you go to their professinal builders link. Even then, you can't find everything, especially stuff like lumber where prices can fluctuate.

[John6012]

Thanks for the reply. I have 1/2 ext wall, 3/4 foam board insulation and 1/4 interior wall. Sure was hoping to use the 1/8" since it'd be easier to work with (and lighter to lift).

[IraRat]

All you have to worry about is the thickness of the wall framing, In other words, is your framing 3/4 thick? Then you just need 3/4 thick insulation.

Also, two thinner layers won't be any easier to install, and you may have gaps, so it's better to go with the one thicker piece. However, if you already have the thinner stuff, go for it.

However, be aware that your ROOF can take more insulation--like an inch and a half, depending on your plans. This is has to do with the way you set the spars/the cross-members there. They're rottated in such a way as to accept an inch and a half.

I myself just stuck 3/4 in there, because I live in balmy South Florida, I have AC installed, and I couldn't make two 3/4 pieces fit in there around the curve without kerfing/cutting the boards--too much work for ME.

Also, the stuff is real easy to lift. It's not heavy at all.

[John6012]

Her's the real deal-sorry I neglected to mention it before but the side window is 1.5" thick making for a 1.5 wall. The front window I'm puting in is a 2 incher. So, I'd rather have the 1/8" ply on the ceiling but... That'll give me 1.5" of insulation on the top. 1/4" luan, 1 1/2" foam board and 1/4 ply rather than the 1/8". I'm trying to figure how in the world I can utilize the 1/8". Could build a sort of 1/8" frame around the front window, that way I could use 1/8" on the ceiling. The side is 1/2" exterior ply, 3/4 foam board and 1/4" oak ply on the interior. I don't mind the 1/4" on the sides but for the ceiling 1/8" is easier to work with. Another way would be use 1/4" only on the front and use 1/8" the rest of the ceiling. Then build a shelf to hide the joint from 1/4" to 1/8".