My client has an attached two car garage and he’d like to convert the bay nearest the house into a mudroom (which will be heated).   The garage slab is about 18″ lower than the floor of the house so the floor of the mudroom will be raised about 11 inches above the slab so there is one step up into the house.  I am trying to work out the details for insulation beneath the raised floor but am stuck on ideas beyond simply laying 2″ thick expanded foam panels directly on the slab.  If the area beneath the new floor is viewed as a “crawl space”, conventional wisdom suggests that it ought to be conditioned, hence, I’m thinking no batts between the joists.  Any thoughts?