Is a building with multiple occupancies considered residential or commercial?

The IECC addresses mixed occupancies by stating that commercial occupancies must comply with the commercial portion of the code and residential occupancies must comply with the residential portion of the code.

ASHRAE Standard 90.1 addresses only commercial buildings. Separate envelope requirements are listed for residential spaces within commercial buildings. Residential spaces are those used primarily for living and sleeping and include dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.