BACnet is the data communication protocol for building automation and control networks, maintained by the ASHRAE Standing Standard Project Committee 135. It models devices as objects with properties and supports change-of-value notifications.
BACnet
BACnet (Building Automation and Control Networks) is how heating, ventilation, lighting, access and fire systems from different vendors talk to each other inside a building. It is maintained by the BACnet Committee, ASHRAE Standing Standard Project Committee 135.
- Objects and properties - Every device is described as a set of standard objects, such as analog inputs or schedules, with readable and writable properties.
- Request and response - A client reads or writes a property with services like ReadProperty, and confirmed services carry their own retries, even over UDP on BACnet/IP.
- Change of value - A client can subscribe to a property and be told when it changes, instead of polling.
- Built for long lifetimes - Buildings run for decades with equipment from many vendors, so interoperability matters more than speed.
For APIs, BACnet is usually the layer underneath: building data reaches cloud platforms, digital twins and energy services through gateways that turn objects and properties into REST, MQTT or GraphQL.
It is one of fourteen protocols mapped to five communication patterns in OT Fabric’s software architect’s guide to OT.
Industry: IoT
