I am planning to take the 1" EPS + plywood sandwich approach to my basement subfloor (pergo on top). I've read conflicting things around the plywood -- is 1/2" ply sufficient? Do I need to do two layers of 1/2" to get to a full 1"?
I don't recommend any wood based subfloor (plywood, osb, particle board, mdf, etc.) in direct contact with your concrete basement floor without first putting down some sort of moisture barrier. I just ripped out an old OSB subfloor (glued right to the concrete floor) in my tiled basement and it had large patches of thick black mold in many places. Many laminate floors suggest use of under-layments that can act as a moisture barrier. If you ever get water in your basement you will regret a wood based subfloor down there (regardless of a moisture barrier installed or not the subfloor will retain moisture for long periods of time). Why not just use a floating floor approach with the underlayment below the pergo?