You have a few things that should be addressed.
Foam board must be protected with drywall, think you will find that's true even with the fire rated stuff.
Both walls should be firestopped, so a fire in your shop can't spread rapidly thru the house. That would be adding wood or drywall on top of those wall to the ceiling.
You have plumbing on the cold side of this, so an insulted drop around the pipe would be the ansewer there.
If you shop is a garage it should be drywalled and taped to seal it up from letting auto off gasses from getting in the house.
Why can't you drywall this area?