Hey Sarah, Code definition 100.1 for conditioned floor area (CFA) is the floor area (in square feet) of the enclosed conditioned space on all floors of a building, as measured at the floor level of the exterior surfaces of exterior walls enclosing the conditioned space. Hope this helps!

Thanks Kaitlin. Thats what I thought, but was hoping they measured inside the walls. Seems like it doenst make sense on thick walled buildings....say a straw bale house. its not space that needs to be conditioned.