As i continue to research and plan for my garage i have come to the point where i am trying to figure out how to insulate the slab. I have read that the epx foam board at 27 bucks a sheet for 2 inch is the way to go. But have also read that the 12 dollar sheets of eps foam will work just as good. The epx is a r-10 and the eps is a r-7.5 in 2 inch think sheets. Has anyone done this before and can tell me witch way to go? Im thinking i will need around 48 sheets so the $15 price difference will add up fast.