Office automation: balancing occupancy, daylight, and comfort

An office floor with a hundred desks should not be lit at full power when only twenty desks are occupied. Constant-light control with daylight sensors and presence detection achieves this with hardware that has been mature for over a decade.

The basic loop: every workspace has a presence detector that publishes occupancy on a KNX group address. A daylight sensor or constant-light controller measures workplane illuminance. A dim actuator ramps the artificial lighting to maintain the target illuminance (commonly 500 lux for general office work). When occupancy goes false for the configured timeout, the lighting fades to standby (often 10 percent) and after a longer timeout to off.

Open-plan offices need zone discipline. A single sensor cannot represent the occupancy state of an entire floor. Group desks into zones of 4 to 8 workspaces, each with its own sensor, and let zones operate independently. Avoid the temptation to chain too many sensors with logical OR; the user experience suffers.

Meeting rooms need different logic. A booking system integration (Microsoft 365, Google Calendar, room booking tablets) tells KNX whether the room is reserved, even if no one has arrived yet. The room can pre-condition five minutes before the meeting (lights on, AC ramping, blinds positioned) and reset five minutes after. Without this integration the user always finds the room cold or hot.

VAV (Variable Air Volume) systems benefit similarly. Tie the VAV box airflow to occupancy and reduce flow when no one is there. The energy savings often pay for the sensors within two years, and the building qualifies for LEED or WELL credits that improve property valuation.