I’m in the process of refinishing my basement and and have recently been studying the pros and cons of the various methods of preparing the finished sub-floor.  One method I like is to install rigid foam directly against the concrete floor, then install 3/4″ sub-floor on top, fastening through the foam with Tapcons.  This is so far my preferred method as I have the ceiling height to accommodate the 2 3/4″ or more that it will take up.  My major hangup with this method though is fastening through the foam – you obviously loose the vapor barrier properties that the foam provides by puncturing it?  Is there a better method?  No moisture issues…. thanks.