eps / xps same?
Many posts have mentioned using 1" XPS or 1" EPS between concrete and framing as a mositure inhibitor. I have always heard EPS had a lower R value but was cheaper. I also heard it came in 4 X 8 sheets. I never saw the product until recently in my local lowes. The tag says Extruded Polystyrene. It looks to me like styrafoam. Its 1" r value is 3.9 compared to an r value of 4 for the pink/blueboard. I can live with the lower r value since I will be adding R13 fg between studs anyway. On each side of the EPS product is a plasticy, shiny material (not foil) that has the product name and says underlayment. Are you suppose to peel this off or just leave it on...it almost like a syran wrap consistency?
Does this EPS truly inhibit mositure as well as the XPS pink board...it is cheaper at $13.50 for a 4x8 as opposed to $8.5 for a 2x8 sheets of the pink board.