Sheetrock over Poly-iso insulation

[greg273]

 I've got some foil-faced insulation left over from another project, and i was wanting to place it in an area of my unfinished house that gets some serious afternoon sunlight (the west wall).  I had originally thought to cut it and place it directly in the stud cavity, with a 1/2 air gap between it and the plywood sheathing, now i'm thinking to just place it over the studs, and nail drywall directly over it.
  Does that sound like an acceptable practice?

[Bart_Cubbins]

I think it might be better to use screws. If the foam has any give to it at all, you might get nail pops just from someone leaning against the wall (i.e. the foam compresses, sheetrock moves in and nail heads pop out of the surface). The screw threads would hold the sheetrock and keep it from being pushed in.

[greg273]

 OK, sorry, I meant use screws.   Sometimes i get a little careless in my verbiage.  A good portion of my house is put together using screws, except for some ringshank gun-nails in the sheeting.
  That was my concern, that the insulation would crush enough to pop the head of the screw out. Well I'l try it and see what happens.
 thanks for the reply!