Section 9.4.1/Lighting Controls
ASHRAE 90.1 Section 9.4.1 covers mandatory lighting control requirements including occupancy sensors, daylight responsive controls, and automatic shutoff.
All interior lighting must have automatic shutoff controls that turn lights off within 30 minutes of all occupants leaving a space. Acceptable methods include occupancy sensors, scheduled automatic time switches, or signal from another control system. Spaces within daylight zones (within 15 feet of vertical fenestration or under skylights) must have daylight responsive controls that automatically reduce lighting power when sufficient daylight is available. Occupancy sensors are required in most enclosed spaces including offices, conference rooms, restrooms, and break rooms.
Why this section exists
Lighting controls address the 30-40% of lighting energy wasted by lights left on in unoccupied spaces and by artificial lighting competing with available daylight. Studies consistently show that occupancy sensors reduce lighting energy by 20-50% in offices and restrooms. Daylight responsive controls can reduce perimeter zone lighting energy by 30-60%. Without mandatory controls, building owners and tenants tend not to install them, locking in decades of wasted energy.
What plan reviewers look for
Plan reviewers check the reflected ceiling plan for occupancy sensor symbols in every enclosed space. They verify daylight sensors in zones within 15 feet of windows or under skylights. They check the lighting control schedule or specification for the automatic shutoff method and the 30-minute timeout. They also verify that the controls are properly zoned (occupancy sensors cannot control lights in adjacent spaces that may still be occupied).
Common violations
Related ASHRAE 90.1 requirements
Section 9.5 covers the lighting power density (LPD) limits. Section 9.4.2 covers exterior lighting controls. Section 6.5.1 covers economizer requirements that parallel the concept of using free resources (outdoor air for cooling, daylight for lighting). IECC Section C405.2 provides equivalent lighting control requirements.