BACnet : Definition

16 November 2023
2 min

Commercial buildings rely on a number of automation devices, making appropriate control and monitoring essential. That's why a building management system (BMS) is so important. How do we manage the interoperability of all this equipment? The BACnet (Building Automation and Control Networks) protocol is one of the best solutions.

What is the BACnet communication protocol in BMS?

BACnet is an open communication protocol standard that is essential for building management. It enables automation devices made by different manufacturers to communicate with each other, increasing interoperability. It also helps centralize monitoring and control data.

More specifically, there are two versions of this protocol:

- BACnet MS/TP. Less secure, slower, and less scalable than BACnet IP, this older version uses Ethernet and standard serial ports. It also involves data storage and transfer to a controller.

- BACnet IP. Favored for its performance, speed and security, this new version uses IP networks and UDP ports. BACnet IP eliminates the need for third-party controllers, allowing for remote control. It is also compatible with all building management systems, including the Wattsense solution.

BACnet goals

BACnet has two goals:

Ensure the interoperability of automation systems, which is crucial for guaranteeing energy efficiency and optimal building management.

Simplify installations and technical management of buildings.

Firstly, this protocol reduces the need for protocol gateways for communication between devices, controllers, and monitoring tools. This greatly simplifies the installation and use of automation devices.

What's more, the building becomes more scalable. Automation devices can even be replaced with models from other brands since BACnet ensures interoperability.

By using this protocol, property owners can freely choose a manufacturer according to their needs and budget — avoiding any dependence on a particular builder.

How does BACnet work?

Let's look at how this protocol works and, more specifically, its application layer, which manages BACnet objects.
In practical terms, objects represent the equipment and data in a building. Each object has several properties, which store different values. A property can be used to access and control other device characteristics.

BACnet services facilitate the exchange of information between systems using a client/server model. They include reading, writing and event notifications.

Let's take the example of an object associated with a temperature sensor. One of its properties can be the current temperature (current value). The service then allows the client to request the current value from the server, and the server responds to the client.

BACnet advantages

BACnet, a truly international standard, is increasingly used in intelligent buildings and connected infrastructures. This protocol offers several advantages — including flexibility, scalability and interoperability — for more efficient building management.

Whereas manufacturers of automation devices and building management systems used to have their own proprietary protocols, all devices now support BACnet IP. With this open protocol, integrators can develop their solutions according to their customers' needs.

This approach also ensures a healthier competitive edge with better project management. For example, the same building may combine HVAC PLCs, an electrical PLC and a control system of different makes. BACnet then ensures the interoperability of the whole system.

BACnet disadvantages

However, despite its many advantages, BACnet still has some limitations and is not suitable for all uses.

Firstly, its simplicity makes it less suitable for master/slave management. It is notably not suitable for managing endpoint devices (convector fans, lighting, blinds, etc.)

Large-scale interoperability is also an issue. A lot of equipment and data saturate the network. As a result, more complex (and costly) network management systems must be put in place. For example, the BACnet protocol is unsuitable when a single method manages several dozen or even hundreds of small controllers.

Examples of BACnet applications

Let's look at some use cases for the BACnet protocol.

Developed by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), while BACnet is primarily used to automate heating, ventilation and air-conditioning (HVAC) systems, it is also used to automate lighting and security systems.

In these areas, it is particularly appreciated for its role in centralizing management. By extension, BACnet also improves the energy efficiency of the building. It provides optimal and consistent remote control of HVAC and lighting equipment. The security system can also be managed more effectively.

Moreover, BACnet makes it easier to maintain technical installations, and to renew them.


As a result, the BACnet protocol has become essential for the automation and interoperability of building management systems. Particularly for HVAC, electrical and security systems.

BACnet is a symbol of openness that has united manufacturers. It offers greater freedom to property owners and integrators. Security, energy efficiency and occupant comfort are just some of the benefits that this protocol contributes to intelligent building management.

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