An area of our basement has rim joists that abutt our garage on one long side, a 3 season room on the other long side and is essentially exposed to outside on the short side. (The 4th side of this area opens to another part of the basement.

I will put the XPS for sure on the side part that is exposed to the outside elements. Am I gaining much of anything buy adding the XPS to the garage and 3 season room sides. These are eseentially under ground, no wind no rain etc etc. Its noticably warmer in the those areas too when I pull back the fg compare to the 3rd short side.

On the other side of the basement (its 'L' shaped) I put 2" XPS in the rims and the fg back on top of that.....but that entire area was more or less exposed to the elements.