How to properly insulate bf Laying hardwood over extension

If you want to repair this right, this is what I would do if it were my home. First off, please don't get your information from an employee from a big box store. There are contractors that will come out and give you an estimate and while they're there, you could ask questions. Second, I see that you didn't use pressure treated joists. You have to get metal flashing under the joists. No kind of wood, except pressure treated should ever be put directly on concrete or stone. Third, I think you're wasting your time and money with the rigid insulation and the fiberglass insulation. Rigid insulation is made to be installed on the under side of the plywood floor not on the ground. Attic insulation could get wet from moisture and grow mold. Instead, I would use spray foam insulation because of the concrete under the floor. After it's sprayed on and expanded, you can use a big knife and shave it down. It will be more money, but it will be money well spent. Fourth, the vapor barrier is fine and you should be good from there to put in your finished flooring. Sorry for the not so good news. Good luck in your new home.

The vapor barrier needs to be on the concrete not on top of the joists. No wood or insulation should come in contact with the concrete. If you can get metal flashing under the joists like Shore grandmom suggests do it. Then put down the vapor barrier. If you can squeeze the vapor barrier under the joist the better than flashing. Then you can put down unfaced fiberglass batt insulation in the cavities. Glue and screw the plywood underlayment on top of the joists. Then go with your flooring. Vapor barrier on top of the joists would trap any moisture from the concrete and cause more problems with the joists.