Yeah we refer to this as the heat loss form factor of the building, which is determined largely by the surface area to volume ratio (so you have a square-cube r

Yeah we refer to this as the heat loss form factor of the building, which is determined largely by the surface area to volume ratio (so you have a square-cube relationship at work) as well as the the number of floors in conjunction with the roof area. With more floors, the heat transfer through the roof (which can be substantial, as mentioned by a sibling comment) is less significant for the same roof area (after normalizing for the gross floor area). Same goes for the slab/foundations (which can also have substantial thermal transfer in many contexts).