Definition of Occupied Space

Jason - I'd love to hear others input on this, but the Reference Guide doesn't seem to define either 'occupied square footage' or the related term 'REGULARLY occupied square footage.' I would assume that the former is effectively the actual interior space of the building (excluding walls, partitions, structural elements, etc...) while the latter further excludes portions of the occupied SF which are not actually occupied by people most of the time - I would exclude the elevator, storage rooms, mechanical rooms etc... and then waffle about what to do with bathrooms and lobbies. Any other ideas out there?