A to Z of Smart Buildings

B: BACnet

Posted by The Comfy Team on May 3, 2016


When you think of smart buildings, BACnet may not be the first thing that comes to mind. As buildings and technology evolve, interoperability (i.e. the ability to play well with others) is essential in enabling new solutions to join existing building ecosystems and expanding smart building capabilities. As the standard communications protocol, BACnet allows building systems and solutions of all ages to stay on the same page; it may quite literally be keeping the lights on in your office. If you want to play in the future of smart buildings, you better speak BACnet.


BACnet: Building Automation and Control Network

A communications protocol for building automation and network controls—enabling a single operator workstation, competitive system expansion, and interoperability.


Published in 1995 (after 8.5 years of development)


ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Standing Standard Project Committee 135


American National Standard 135.1 (since 1995)
ISO global standard 16484-5 (since 2003)
European standard
National standard in 30+ countries


60% of all buildings and rising


One more time, what is BACnet?

BACnet is a framework and set of standard operations for systems in the building space to communicate with one another. BACnet is used across building automation systems—both hardware and software, made by various vendors—including HVAC equipment, lighting control, security, and others. Think: Smart building playground rules for multiple applications and networks (regardless of system type, maker, or age).

Why was it developed?

Up until the 1980s, building controls and system languages were predominantly vendor proprietary, meaning building automation systems from different vendors spoke different languages, were not created with compatibility in mind, and lacked guidelines to function with one another. BACnet was established to standardize system interoperability (allow for mixing and matching of vendors), focus on a single control center for building operators, and open the doors for competitive systems and services (like software applications) to connect to existing building systems.
Fun Fact

For three to four years BACnet was referred to by SPC engineers as “the ASHRAE protocol.” Other name ideas included “ASHnet” and “BACtalk,” before they settled on BACnet.


Here are the deployment elements.

Device Interoperability Components:


How to represent information, or pieces of information, such as binary, analog, or algorithm.

Example: 1= Fan on, 0= Fan off, or Setpoint= 72.


How to make requests and interoperate between one BACnet device and another, in order to do something.

Example: Write, change alarm state, trend data.


Electronic messaging and internetworking standards and methods that convey coded messages between BACnet devices.

Example: BACnet/IP, ARCNET, Ethernet.

Service Interoperability Areas:

Data Sharing | Trending | Scheduling | Alarm & Event Management | Device & Network Management

Do all buildings use BACnet?

No, but there are workarounds. There are still a number of vendor-specific building control protocols, which was the impetus for the creation of BACnet. Some buildings are “Native BACnet,” meaning the BACnet messages, services, and data model trickle throughout the building control system. Most current generations of buildings control equipment are BACnet compatible (i.e. Honeywell, JCI, Siemens, Schneider). There are some systems that don’t speak BACnet natively, such as LonTalk based systems, but in those cases BACnet gateways (think: intermediate/translator boxes) can be used to translate from legacy protocols (non-BACnet) to BACnet, and back again.

Is this concept unique to commercial buildings?

Communication protocols, like BACnet, are found across other industries and communication channels. For example, protocols exist for email, calendaring, and telecommunications. However, unlike other industry protocols, BACnet specifies the entire stack (all levels) of the device communication architecture. Meaning it provides structure and guidance on building system communications, from soup to nuts.

What does BACnet mean for the future of smart buildings?

Buildings have wires in the walls, ducts in the ceilings, and BACnet guiding the systems. As buildings evolve, BACnet allows new technologies and solutions to layer onto the existing building infrastructure, while maintaining central control (and sanity) for building operators. As new technologies and systems are introduced to improve the building experience for the people that work in them, BACnet will be the common denominator for plugging into buildings’ ecosystems.


Thanks to bacnet.org for an abundance of information, and of course the brain of Stephen Dawson-Haggerty, Co-Founder and CTO of Building Robotics.

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