I want to insulate my concrete block basement walls with foam board insulation, and use furring strips to install paneling. My question is 1) Iinstall the furring strips 16" on center and insulate between each strip? 2) Insulate the entire wall first, then place the furring strips on top? If (2) above, then what do you do with the gap that will end up between the foam board and paneling? Lastly, using foam board, is it still necessary to use a vapor barrier? I know it is if using fiberglass batting, but not sure if needed with foam board.