Use the rigid foam against the concrete, before you frame the walls.

Oh I see, you mean cover the concrete completely and build the frame wall on top of it? OK. Questions:

What's the best way to attach the foam to the concrete? Adhesive?

How should I secure the framed wall? Concrete anchors of some kind on the bottom I assume. At the top, there is a bit of the top of the concrete wall exposed (ledge) where the upper wall plate did not cover it all the way, so I could lay a horizontal piece of wood to cover that strip of concrete, and the top edge of the foam, and the top of the framing, all at once. Toenail that into the bottom of the upper wall that sits on top of the skirt wall. That would tie in the top of the stud wall to something solid.

Adhesive for the foam, either tapcons or powder actuated gun for the framing. there's some good info here:

https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall

Found a spec sheet for the board, says you can use dots of construction adhesive or concrete nails/screws. I like the adhesive, quick and easy and then I'd snug the stud wall up to it.

https://www.jm.com/content/dam/jm/global/en/building-insulation/Files/BI%20Toolbox/BID-0148_AP_Foil_Residential_Installation_Instructions-Below_Grade_Interior_Walls.pdf

Make sure you use a "sill gasket" under the walls to separate the wood from the concrete.

Wood should never have direct contact with concrete.

I installed Dupont Foamular board directly against the concrete walls, using Liquid Nails (IIRC) to stick it to the concrete. I used temporary bracing to hold it against the wall until the adhesive set up, and just worked my way down the wall. I then taped all the seams with Tyvek tape and spray foamed any gaps that couldn't be easily covered by the foam board. Mine was in a basement, so I also cut foam board and used it with spray foam to insulate the rim joist.

Then I framed a 2x4 wall right up against the foam board, with a foam gasket under the pressure treated bottom plate of the framing. I squared up the framing and then shot nails into the floor with a gun to hold the bottom, and nails into the joists above to hold the top. The framing is not attached to the wall, and there are no penetrations through the foam into the block wall. The electrical wiring was run between the framing and the foam board, or through holes near the back edge of the 2x4.

I then installed rock wool insulation between the studs to provide additional insulation. When I installed the drywall I kept the bottom about 1/2" off the concrete so it would not absorb moisture. When the baseboard molding was installed it was spaced about 1/4' off the floor.

I just cleaned up the floor with water and Simple Green, and painted it with gray concrete paint from HD. As the paint wears I'll just put on another coat.

Bruce

Sounds great, all makes sense to me. I like the spray foam, I use that already on various things and it's very handy. I haven't used the Tyvek tape but I'm sure I can find it. The spec sheet on the foam board mentioned taping joints with a certain type of tape I can't recall at the moment. I'll make sure to get something appropriate.

I think I'm on my way! Thanks everyone.