Insulation for concrete partition wall in basement – GreenBuildingAdvisor

I have a poured concrete partition wall in my basement (see attachment). The side facing the large room will be insulated the same as the inside faces of the exterior walls (1″ XPS, stud wall with 3-1/2″ Rockwool, and DensArmor drywall), as it will have an electrical panel and plumbing anyway.

My question is what to do on the side facing the laundry room. That side will have solar equipment and batteries mounted on it. For fire safety, I’d like to not use foam board, even behind drywall, in that room with the solar equipment.

It’s an interior partition, but it is physically joined to the exterior wall at one end, and it sits on a footer below. The basement is about 3′ exposed and 6′ below grade. I’m in CZ 4 marine, where the ground temp is about 55 deg. It is not coupled to the slab — the slab has 2″ XPS underneath and 2″ XPS horizontally between it and the walls.

There does not appear to be any code requirement to insulate it, although there will be some amount of heat-loss through it. I’m considering for the laundry room side 1) leaving the bare concrete uninsulated, or 2) attaching 1 or 1-1/2″ Comfortboard behind DensAmour. I feel that I’d be able to air seal that (SmartRock starts at 2″, and I don’t want to loose that much interior space), or ?

Thanks!