BACS Decree: Is Your Building Really Ready?

Who it’s for: Owners, managers and operators of commercial buildings, as well as design offices. The approach also applies outside France.

"BACS? Another new regulatory requirement?"

This is often the first reaction when the BACS Decree comes up.

And yet, reducing the topic to a new requirement would mean missing the point entirely.

BACS is not simply about installing a supervision system or a few communication devices.

It raises a far more interesting question:

Is your building genuinely able to measure, understand and control its technical systems?

BACS: What Are We Really Talking About?

BACS stands for Building Automation and Control Systems.

In France, the scheme applies to non-residential (tertiary) buildings equipped with a heating or air conditioning system, whether or not combined with ventilation, where the effective rated power exceeds 70 kW. The requirements and their timeline vary in particular according to the power level, the date of the building permit, and whether the building is new or existing.

Two thresholds are particularly important to understand.

Above 290 kW

For existing buildings concerned whose heating or air conditioning systems exceed 290 kW, the deadline was set at 1 January 2025: these buildings must therefore already be equipped.

For new buildings concerned, the requirements apply based on the date the building permit was filed.

At this power level, the scheme provides in particular for connecting the building's technical systems to the automation and control system when the regulatory and economic conditions are met.

Between 70 and 290 kW

The 70 kW threshold considerably widens the scope of the scheme.

For new buildings concerned, the requirements apply according to the date the building permit was filed.

For existing buildings concerned, the requirement applies when the heating or air conditioning system is renewed, and at the latest by 1 January 2030 (a deadline originally set for 2027 and postponed by the decree of 26 December 2025), unless a study shows that the installation cannot achieve a payback period of less than ten years.

These two thresholds should therefore not be read as mere figures.

They correspond to different regulatory situations.

And above all, they do not replace an analysis of the building.

BACS ≠ Just a BMS

This is probably the first confusion to avoid.

A BMS can display temperatures, equipment status, alarms or consumption.

But the BACS requirements go further.

The system must in particular make it possible to track, record and analyse energy data, assess system efficiency, detect certain losses of efficiency and adjust the operation of technical systems accordingly. It must also allow interoperability with the building's various technical systems.

In other words:

displaying data is not the same as using it.

A screen showing that a zone's temperature is 24°C does not, on its own, make the building smart.

The real value appears when the system can understand this information, compare it to a reference, detect a drift and enable an appropriate action.

The Trap: Connecting Equipment Without Thinking About the Architecture

This is where BACS projects become genuinely interesting.

A building may already have several systems:

heating;
air conditioning;
ventilation;
lighting;
energy metering;
energy production;
electrical equipment;
blinds;
specific technical equipment.

These systems may use different technologies and protocols: BACnet, Modbus, KNX, DALI, M-Bus or other interfaces.

The temptation is then to look for a solution capable of "connecting everything."

But connecting is not designing.

Before choosing protocols and equipment, it is necessary to determine:

What data do we need to collect?
At what frequency?
For which zones?
What decisions do we need to be able to make?
Which equipment do we genuinely need to be able to control?
And above all: who will use this information tomorrow?

It is this thinking that should define the architecture.

The technologies come afterwards.

A Building Can Measure a Lot... and Still Function Poorly

Imagine a commercial building where the supervision system displays:

temperatures;
consumption;
equipment status;
alarms;
operating hours.

On paper, the building appears perfectly instrumented.

But if no one knows what to do when consumption rises abnormally, if the schedules don't match actual occupancy, if a setpoint remains needlessly low or high, or if a drift is never addressed, the data simply remains... data.

Measuring an anomaly is not the same as knowing what to do about it.

This is a fundamental difference between an installation that collects information and a system genuinely oriented towards energy performance.

BACS Starts With Data

A relevant architecture must enable a genuine loop:

Measure → record → analyse → detect → act → verify.

And this loop must function over time.

The regulatory framework provides in particular for tracking energy data by functional zone at an hourly time step, as well as its retention in accordance with the arrangements set out in the text.

This changes the way the project should be designed.

It's no longer enough to ask:

"Which BMS are we going to install?"

It's also necessary to ask:

"Which data do we want to keep, and what decisions do we want to be able to make with it?"

And This Is Where the Existing Building Becomes Decisive

Two buildings subject to the same scheme can be in completely different situations.

The first already has:

a communicating HVAC regulation system;
accessible meters;
a supervision system;
interoperable equipment;
proper technical documentation.

The second has equipment from different generations, proprietary regulation systems, little metering, incomplete documentation and several independent systems.

Both may be subject to BACS.

But their path to compliance will obviously not be the same.

This is why the first task should not be to choose a solution.

It should be to carry out an assessment of the current situation.

Before Talking About BACS, Look at Your Building

A few questions can already help gauge the situation:

What heating and air conditioning systems are installed?
What is their power?
Which equipment already communicates?
What protocols do they use?
Is there a supervision system?
What consumption is actually measured?
Is the data accessible to the owner?
Can the equipment be controlled automatically?
Are the functional zones properly defined?
Is technical documentation available?
What happens if communication is lost?
Who will use the data once the system is installed?

These questions are often more important than the initial choice of a BMS brand.

The Real Cost of BACS

The mistake would be to see BACS as simply the price of a BMS.

The real cost can include:

audit + architecture + equipment + communication + integration + programming + commissioning + metering + supervision + documentation + maintenance.

And above all, the cost of operation must be factored in.

A complex system that no one consults or properly understands can represent a significant investment without delivering the expected value.

Conversely, an architecture designed around usage, data and operational needs can become a genuine tool for managing the building.

BACS Should Not Be a Box-Ticking Exercise

This is probably the best way to sum up the topic.

BACS should not be treated as:

"We need to install a BMS because the regulations require it."

But rather as:

"The building must be able to measure, understand and control its technical systems in order to durably improve its operation."

The regulations set a framework.

Engineering is about turning that framework into a genuinely usable architecture.

At ExaBuilding, we approach a BACS project by starting with the existing situation, the uses, the technical systems, the available data and the building's objectives.

We then define the communication, supervision and control architecture suited to the project.

Because a smart building is not the one with the most sensors or the most attractive supervision system.

It's the one that turns its data into useful decisions.

To Learn More

Presentation and guide to the BACS Decree (Official French Government portal)