See pictures as the deck is close to the ground about a foot on one side and 6 inches on the other looks like the former owner put some sort of tarp on the ground.
How to insulate between floor boards.
The correct method of using rigid foam is to run continuous 4 foot by 8 foot sheets of the foam across the concrete basement wall making the rigid foam the de facto wall.
Add wire insulation hangers as needed to.
After that thin furring strips are installed on top of the foam to provide a firm base for the drywall screws and drywall but can you run rigid foam between the studs just as you would do with fiberglass rolls or spray foam.
One side we can crawl under on the other side we will need to take up the deck boards.
Next you will need to place the foam board insulation between each joist as a test.
Transfer each measurement to a 4 by 8 foot sheet of rigid foam insulation.
If it fits proper with no space between on either side of the board pick it up and put a thin layer of glue on.
Cut your insulation to size using a utility knife.
Add an insulating layer under.
Step 2 score a line on the metal backing with a utility knife then cut along the line with a drywall saw to make pieces of rigid foam that will fit between the joists.
If it you need to spread it use a brush to help cover and smooth out the glue.
In most parts of the united states insulating the exterior edge of a slab can reduce heating bills by 10 to 20.
Place it into the space between your existing floor joists relying on friction to hold it in place.
Working from the crawlspace measure the distance between the floor joists with a tape measure.
Installing roll insulation in ceiling of basement which is under floors of living space my basement is heated but a smaller amount than up in living space usually 66 68 upstairs and 58 60 at the same time in basement my question is about the kraft paper facing i think it should face the basement because of any moisture in basement.