From 2009 IECC as well as above505.2.2.2 Automatic lighting shutoff. Buildings larger than 5,000 square feet (465 m2) shall be equipped with an automatic control device to shut off lighting in those areas. This automatic control device shall function on either:
1. A scheduled basis, using time-of-day, with an independent program schedule that controls the interior lighting in areas that do not exceed 25,000 square feet (2323 m2) and are not more than one floor; or
2. An occupant sensor that shall turn lighting off within 30 minutes of an occupant leaving a space; or
3. A signal from another control or alarm system that indicates the area is unoccupied.
Exception: The following shall not require an automatic control device:
1. Sleeping unit (see Section 505.2.3).
2. Lighting in spaces where patient care is directly provided.
3. Spaces where an automatic shutoff would endanger occupant safety or security.
You have to meet both sections Occ sensors do, so IMO, they are easiest...