house is slabish on grade, built into a hill so the back wall has about 6' of dirt against it.

looking to install hardwood on a slab (on grade) here is what i am thinking of doing:

6-15mil poly > 1/2" poly iso > 5/8" Plywood (or osb?) > Insulayment or Quiet floor (has vapor barrier) > nail down t&g 3/4 hardwood or 3/8".

Would screw the ply to the slab thru the foam.

I also was thinking of just using 1-3 strapping with 3/4 iso in between as the subfloor but i think the strapping to concrete would defeat the whole purpose of warming the floor. This would be cheaper.

Any comments or criticism is appreciated