A change of use to a restaurant would likely use more energy and require the building to be brought into full compliance with today's energy code...
Spaces undergoing a change in occupancy that would result in an increase in demand for either fossil fuel or electrical energy shall comply with this code. Where the use in a space changes from one use in
Table C405.3.2(1) or
C405.3.2(2) to another use in
Table C405.3.2(1) or
C405.3.2(2), the installed lighting wattage shall comply with
Section C405.3. Where the space undergoing a change in occupancy or use is in a building with a
fenestration area that exceeds the limitations of
Section C402.4.1, the space is exempt from
Section C402.4.1 provided that there is not an increase in
fenestration area.