I'd like to use Styrofoam insulation to insulate my cathedral ceiling (10' wide x 21' tall bays). I have not used this insulation before and I'm wondering about installation, especially since I'll have to put some type of strapping in the middle of the bay to attach drywall to.
Has anyone used/installed styrofoam in a similar case?
I have used polyiso. in conventionally framed (16" OC) cathedrals. What I get here is that your spans are 10' as opposed to 16". Styro has an initial R value of about 1/2 of this stuff and was thus rejected by myself. Remember, all of it outgasses, thus droping the R val. The toughest one I did was framed with 2X6s, so I banged some 6p commons into the rafters 1/2" down from the roof sheathing, ripped and installed two 2" layers of material interspersed with fiberglass to fill the irregularities and then went across the faces of the rafters with 4X8 sheets of 5/8" Polyiso behind the sheetrock, foil taped. Yeah, yeah- I can hear some of you spray on people already typing, but this was the rockin' and rollin' 80s here in Upstate NY. Plus the help in my local lumber yard were a bit careless and now and then damaged a few sheets. And yeah- I know that's tight for roof ventilation, but I'm big on energy and when I reroofed one of these, I went with a light color to reduce the heat, plus adding framing downward was out of the question. All seems well so far. The only thing I would report further is that if you intend to attach anything into the framing members behind the s/r, the 5/8" polyiso will compress enough to pop nails or screws if you don't have the right touch.