BACnets

BACnet, short for Building Automation and Control networks, is a data communication protocol designed for building automation systems. It provides a vendor-neutral standard that enables devices and software from different manufacturers to exchange information and coordinate control of building functions such as heating, ventilation, air conditioning, lighting, and security. The BACnet protocol is maintained by ASHRAE and is internationally standardized as ISO 16484-5.

BACnet is built around an object-oriented data model. It defines numerous object types, including Analog Input, Analog Output, Binary Input, Binary Output, and Multistate Input, each with properties that describe status and control points. Applications interact with objects using services such as ReadProperty, WriteProperty, and I-Am for device discovery, as well as SubscribeCOV for event-driven updates. This model supports interoperability across equipment from different vendors.

The protocol supports multiple network media, including BACnet/IP over Ethernet or Wi‑Fi, BACnet Ethernet, and BACnet MS/TP for RS-485 serial networks. Routers and bridges enable communication across disparate networks, enabling large-scale building automation. Security has evolved to include BACnet Secure Connect (BACnet/SC), which provides encrypted and authenticated connections, in addition to established authentication and access controls.

Standards and certification: The original standard, ASHRAE 135, defines BACnet in detail; ISO 16484-5 later adopted the protocol for international use. The BACnet Testing Laboratories (BTL) certify interoperable implementations to facilitate vendor compatibility. BACnet has wide adoption in commercial buildings, campuses, and industrial facilities, supported by a broad ecosystem of devices and software tools that implement the protocol.