Lighting Systems Save More Energy Through HVAC Integration

By Szymon Slupik, President & CTO, Silvair

Energy saving is the primary feature of lighting control systems. The concept is well known: dim the lights if there is enough sunlight (daylight harvesting controls) or turn the lights off when there are no people in the room (occupancy / vacancy – based controls). The more granular the controls are – the better, with luminaire-level lighting controls (LLLC) being the ultimate setup that assumes an occupancy sensor in every luminaire.

Heating, ventilation, and air conditioning (HVAC) systems have lacked this level of granularity for years – traditionally HVAC systems run on fixed schedules. This means that the system is either on (during business hours) or off otherwise. Very often pumping cooled or heated air through empty spaces.

The ASHRAE/IES standard 90.1 has introduced the concept of Occupied Standby (90.1-2019/2022). It allows to power down the system (down to the zone level), even during workdays, if the zone is empty. There are two defined behaviors:

• Zero ventilation: if allowed by ASHRAE 62.1 (Air Quality), the ventilation airflow can be reduced to zero. Less airflow means less energy used to cool or heat the circulating air.
• Setpoint deadband widening: the thermostat deadband can be widened, which reduces the frequency at which the HVAC system is activated. For example, the AC might stop cooling until the room hits 78°F instead of 72°F, reducing the load on the chillers.

If only the HVAC had the needed granular information about zone occupancy… Typically they don’t, as HVAC zones are typically large and have very few sensors. But what if they could be linked to the dense grid of LLLC occupancy sensors? This is exactly the concept of lighting-HVAC integration.

The ASHRAE/IES 90.1 Section 6.5.3.8 Occupied-Standby Controls says:

Zones serving only rooms that are required to have automatic partial OFF or automatic full OFF lighting controls per Section 9.4.1.1, where the ASHRAE Standard 62.1 occupancy category permits ventilation air to be reduced to zero when the space is in occupied-standby mode, and when using the Ventilation Rate Procedure, shall meet the following within five (5) minutes of all rooms in that zone entering occupied-standby mode.

1. 1. 1. Active heating set point shall be setback at least 0.5°C.
      2. Active cooling set point shall be setup at least 0.5°C.
      3. All airflow supplied to the zone shall be shut off whenever the space temperature is between the active heating and cooling set points.

There are two ways to implement the integration. In large buildings HVAC is controlled by a building management system (BMS) that runs on the BACnet protocol. The integration is done with the help of a BACnet gateway that translates the protocol used by a lighting system (such as Bluetooth^® NLC) to BACnet. The gateway represents the lighting occupancy sensors as BACnet objects and allows the BMS to feed the sensor information to the HVAC system.

While large buildings (defined as over 50,000 ft²) constitute 50% of commercial square footage, they count only as 6% of buildings. The other 50% of square footage – 94% of buildings do not have any BMS. They usually have just a single roof-top unit (RTU) and (in the best case) a couple of thermostats. They operate on fixed schedules.

There is a new generation of thermostats designed to address the opportunity of integrating LLLC sensors with HVAC. These thermostats are capable of directly receiving signals from lighting occupancy sensors, taking advantage of this highly granular, dense sensor grid.

Standardization helps here with cross-vendor interoperability. In 2025 the Bluetooth SIG adopted the HVAC Integration NLC Profile specification, which defines the standard for wireless thermostats to receive and interpret information from occupancy sensors that are compliant with the Occupancy Sensor NLC profile (see the Bluetooth blog and the specification).

During commissioning the thermostat controlling a HVAC zone is added to the lighting system and logically linked with one or more lighting zones (typically lighting zones are more granular than HVAC zones). The thermostat can then follow the ASHRAE Occupied Standby behaviors: incrementally widen the setpoint deadband and reduce / shut down ventilation when the lighting system reports reduced occupancy (or no occupancy).

Figure 1, above, Integration through a BACnet Gateway. Image courtesy of Silvair.

Figure 2 Direct integration of a wireless thermostat with wireless LLLC occupancy sensors. Image courtesy of Silvair.

About The Author

Szymon Slupik is President & CTO at SILVAIR. He has also been chairing the Mesh Working Group at Bluetooth SIG, and has been the key contributor to Bluetooth NLC specifications, including the HVAC Integration NLC Profile. He has been active with several standardization bodies including the ANSI C137 Lighting Systems Committee, the BACnet committee, and the DALI Alliance.