Lighting Goes HVAC

The IES Annual conference has always been the temple of light. Stunning designs, beautifully illuminated spaces, and the role of light in human wellbeing. In 2025 this has changed. The Gala and the Awards were still about illumination, but the technical sessions started to boldly drift away, to discuss - surprise, surprise - heating, ventilation, and air-conditioning. All with connection to light of course. Or - to be precise - to occupancy sensors brought to buildings en masse thanks to lighting.

HVAC is shaping up to be the first significant beyond-lighting application. Forget wayfinding beacons. Forget asset tracking. Forget space utilization heatmaps. It is still all about energy savings. The lighting folks realized the HVAC crowd was unable to pull it on their own. So have come to offer the helping hand: the Lighting-HVAC Integration.

As I cried almost 10 years ago - for the connected products to get really connected, we need cross-domain industry experts. And this has been happening now - at least in commercial lighting we have started building bridges between lighting and HVAC. At the IES25: The Lighting Conference, two presentations stood out:

1. Why is it challenging to integrate lighting and HVAC systems, and how can those challenges be overcome? by Michael Poplawski, the Chief Engineer at Pacific Northwest National Laboratory.
2. LLLC, DALI, & HVAC: Finding New Purpose in the LED Era by Chris Wolgamott, NEEA, Carol Jones, DALI Alliance and Michael Myer, PNNL.

Michel dived deeper into the dialogue between lighting at HVAC systems (also highlighting the recently adopted Bluetooth NLC HVAC Integration Profile), focusing on simulation of two potential scenarios when lighting occupancy data is linked to a HVAC zone:
- ALL – the HVAC zone is occupied if ALL lighting sensors in the zone detect occupancy – presence.
- ANY – the HVAC zone is occupied if ANY lighting sensor in the zone detects occupancy – presence

Michael and Chris went deeper into what really happens in-between the edge ALL and ANY strategies, arguing the proportional HVAC response tied to partial occupancy is where most of the energy savings potential can be identified.

The keyword here is the "Occupied Standby", covered by ASHRAE/IES 90.1 (6.5.3.8), IECC 2024 (C403.7.8) and California Title 24 (120.1(c)5).

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

Now the proportional / partial occupancy control is about widening the set point window, from the default 1°C (+/-0.5°C) up to perhaps 2°C or 3°C at most, depending on the HVAC system response and the perceived occupants' comfort. As of now, NEEA has been running several pilot projects and gathering data. I'm sure we'll see more of this. The technology is there and already covered by building standards such as BACnet and Bluetooth® NLC. We just need to gather more data to give practical guides to the installers. And perhaps have the partial occupancy visualized by thermostats to see the system works as intended.