Lighting controls are one of those topics where the gap between what building owners know and what the technology can do is unusually wide. Most people are familiar with occupancy sensors and programmable light switches, but commercial lighting controls have evolved considerably, and the integration possibilities with a building automation system go well beyond what most buildings are taking advantage of. Lighting is typically 20-30% of a commercial building's energy consumption, and well-designed controls can reduce that by 30-50%. That is a significant number.
The Technology Options
Occupancy and vacancy sensors are the most common entry point into automated lighting control. An occupancy sensor turns lights on automatically when it detects motion or presence in a space, and turns them off after a defined timeout period. A vacancy sensor requires someone to manually turn the lights on but turns them off automatically. Energy codes increasingly favor vacancy sensors in certain space types because they prevent lights from turning on when daylight is sufficient or the space is already lit.
Sensor technology has evolved. Passive infrared (PIR) sensors detect body heat and movement but have a narrow field of view and can miss occupants who are sitting still. Ultrasonic sensors emit high-frequency sound waves and detect motion through Doppler shift; they are more sensitive to small movements but can false-trigger on air movement from HVAC diffusers. Dual-technology sensors combine both approaches, requiring both PIR and ultrasonic detection to confirm occupancy, which reduces false-offs and false-ons.
Photocells and daylight harvesting use light sensors to measure actual illuminance in a space and dim or switch off electric lights when daylight provides sufficient illumination. A properly designed daylight harvesting system adjusts electric lighting continuously throughout the day as the sun moves and cloud cover changes. The energy savings potential in perimeter zones with significant window exposure is substantial, often 30-50% of that zone's lighting energy.
Time-based scheduling is the most straightforward approach: lights follow a programmed schedule tied to the building's occupied and unoccupied periods. This is the right baseline control for spaces where predictable schedules justify a simple approach, and it is a minimum requirement under most energy codes for automatic shutoff.
Dimming controls allow fixtures to operate at any level between 0 and 100% rather than just on or off. The two dominant dimming protocols in commercial applications are 0-10V analog and DALI (Digital Addressable Lighting Interface). 0-10V is simpler and less expensive; a 0-10V dimmer sends a voltage signal to a compatible driver, with 0 volts at minimum light and 10 volts at full output. DALI is a digital protocol that allows bidirectional communication with each individual fixture, enabling fixture-level addressing, status feedback, and more sophisticated control capabilities.
Relay-based zone control switches entire circuits or zones of lighting on and off through a relay panel, typically controlled by a lighting control system or the BAS. This is common in large open spaces where individual fixture control is not required.
How Lighting Controls Integrate with Your BAS
The integration options between lighting control systems and a BAS range from simple to sophisticated.
Dry contact integration is the most basic approach. The BAS sends a voltage-free relay output to a lighting panel, which interprets the contact closure or opening as a command to switch a zone on or off. It works reliably and requires no shared protocol, but it is limited to binary on/off control with no feedback.
Modbus integration is common with relay panels and some intelligent lighting controllers. The BAS communicates with the lighting panel over a Modbus RS-485 connection, allowing it to read zone status, issue switching commands, and in some cases read energy data.
BACnet integration is the most capable option and is increasingly available from lighting control system manufacturers. With BACnet, the BAS and the lighting system speak the same protocol, enabling real-time bidirectional communication, occupancy data sharing, and unified scheduling. An occupancy sensor reading from a ceiling-mounted sensor can be shared with the HVAC controller for the same zone, allowing the BAS to adjust ventilation and temperature setpoints based on the same occupancy signal the lighting system is already processing.
Energy Code Requirements
Both the IECC (International Energy Conservation Code) and ASHRAE 90.1 have lighting controls requirements that apply to commercial buildings. The requirements have become progressively more stringent over recent code cycles.
Automatic shutoff is required for most commercial spaces: lighting must be automatically turned off within a specified time after the space is vacated. Specific spaces like parking garages, corridors, and stairwells have their own requirements. Daylight-responsive controls are required in spaces that receive significant daylight through windows or skylights, with specific requirements for sidelighted and toplighted zones. Exterior lighting has its own automatic controls requirements for on/off control based on astronomical time clocks.
Louisiana's building code references these standards, and compliance with lighting controls requirements is reviewed during the permitting and inspection process for new construction and qualifying renovations.
Common Mistakes We See
Occupancy sensor placement near HVAC diffusers. An ultrasonic sensor mounted close to an HVAC supply diffuser will detect the air movement as occupancy and keep lights on in empty spaces indefinitely. Sensors should be located away from supply diffusers and return air grilles.
Timeout settings that do not match space use patterns. A conference room with a five-minute timeout will turn the lights off on people sitting still during a presentation. A private office with a thirty-minute timeout wastes energy when someone steps out for a meeting. The timeout setting should be calibrated to how each space is actually used.
No commissioning of daylight harvesting calibration. A daylight sensor that is not calibrated to the actual light levels in the space will either keep electric lights on when daylight is sufficient (wasting energy) or dim them below acceptable levels when occupants are present (causing complaints). Calibration is a required step, not optional.
Ignoring the integration opportunity. A lighting control system and a BAS that operate independently miss the opportunity to share data. Occupancy information, schedule coordination, and demand response capability all improve when the two systems are integrated.