BMS class B or class C: how to choose for your HVAC systems

With the French BACS decree and the growing focus on energy efficiency, building automation (BMS) is no longer optional for many commercial buildings. One question keeps coming up: should you aim for class B or class C? Let's break it down.

BMS classes under the standard

The NF EN ISO 52120-1 standard (which replaced EN 15232) defines four efficiency classes for building automation and management systems: A (high performance), B (advanced), C (standard, the reference) and D (non-efficient, to be avoided).

Class C: the standard

Class C is a BMS providing the basic functions: HVAC equipment control, time scheduling, simple centralised management. It's the reference level against which the gains of higher classes are measured.

Class B: advanced control

Class B adds finer, communicating control: room-by-room terminal control, lighting and blind management based on occupancy, detailed metering, drift detection. For your HVAC systems, that means terminal control with feedback and better coordination between systems.

What the regulation says

The French BACS decree requires a BMS for commercial buildings whose HVAC system power exceeds certain thresholds, with progressive deadlines. In practice, it pushes the building stock towards class B. Check the thresholds and dates in force for your project, as they change.

How to choose

• Regulatory obligation: if the BACS decree applies, class B becomes the target.
• Return on investment: class B costs more to install but generates significant energy savings over time.
• Size and use: the larger the building and the more variable its occupancy, the more relevant class B becomes.

In short

Class C remains an acceptable base for small buildings outside any obligation; class B becomes essential as soon as regulation or the search for savings comes into play. The right reflex: frame the BMS target from the design phase, trade by trade.