What Is an Occupancy Sensor?
An occupancy sensor is an electronic device that detects the physical presence or absence of people in a specific room or building zone. While they are commonly associated with turning lights on and off, in a commercial HVAC context, occupancy sensors communicate with building controls to automatically adjust heating, cooling, and ventilation based on real-time room usage.
Types of Occupancy Sensors
Occupancy sensors are available in several technologies; some work better for specific purposes than others.
- Passive infrared (PIR): Detects changes in infrared radiation from warm bodies in motion. This technology is good for line-of-sight coverage and is low cost.
- Ultrasonic: Emits high-frequency sound and detects motion from reflected waves. Can detect movement around obstacles but is more prone to false positives.
- Dual technology (PIR + ultrasonic): Combines two types of sensors to reduce false triggers and improve reliability.
- Radar/mmWave (Doppler or Frequency Modulated Continuous Wave): Sensitive to micro-movements and works in darkness and through some obstructions. These are useful for restrooms and corridors.
- Camera-based/vision analytics: Provides detailed presence/counting and behavior analytics but raises privacy concerns and often costs more.
- CO2 sensors (indirect occupancy): Infer occupancy from CO2 concentration for demand controlled ventilation (DCV). This kind is best used with direct occupancy sensors or as a complement to other kinds of sensors.
- Vibration/pressure/PIR hybrids: Used in seats and meeting rooms to reliably detect occupant presence.
How Occupancy Sensors Are Used in Smart Buildings
In commercial spaces, such as office buildings, schools, and hospitals, occupancy levels fluctuate constantly. Rather than running the HVAC system at full capacity based on a rigid 9-to-5 schedule, occupancy sensors allow the system to operate dynamically. When a sensor detects that a space is empty, it signals the HVAC controls to initiate energy-saving measures, which typically include:
- Temperature setbacks: Relaxing the heating or cooling setpoints by a few degrees (for example, allowing an empty conference room to get slightly warmer in the summer).
- Airflow reduction: Signaling Variable Air Volume (VAV) boxes to reduce the amount of conditioned air being pushed into the unoccupied zone.
- Demand-controlled ventilation: Reducing the intake of outside air to the room, since fewer people means lower carbon dioxide (CO2) exhaust and less need for fresh air turnover.
- Analytics and space utilization: Aggregate occupancy data to support space-planning, cleaning schedules, and operational decisions.
You Can Integrate Occupancy Sensors with These Systems
- Building automation systems (BAS): They integrate seamlessly with centralized platforms like Trane Tracer® Ensemble™ or Tracer® SC+, allowing facility managers to view real-time occupancy data and track energy savings across the whole building.
- Unit-level HVAC controllers: They can wire directly into terminal equipment like VAV boxes, fan coil units (FCUs), or water-source heat pumps (WSHPs) for localized control.
- Lighting control systems: A single occupancy sensor can often be shared over a network, like BACnet®, to control both the room’s lighting and the HVAC system simultaneously.
- Room scheduling software: Sensors can be linked to digital room-booking platforms. If a meeting room is booked on the calendar but the sensor detects no one is there, the HVAC and lighting can remain in energy-saving modes.
Adding occupancy sensors can help improve your building's energy efficiency and enhance its comfort. Contact your local Trane representative to learn more about how you can integrate these sensors into your existing facility or new construction.
