BACnet is a data communication protocol for Building Automation and Control Networks. It is a standardised technology for building automation and supports a variety of specific physical network standards, which makes it ideal for use on all automation levels.

The BACnet technology is an international standard of data communication technology used in building automation and building management systems (BMS) worldwide.

Open technology
BACnet is an open technology which means that any manufacturer can use the protocol to transfer data of connected devices like pumps, valves, boilers, chillers, fans, sensors, etc.
Being designed specifically for building automation, BACnet has an advantage in this specific area over many of the other fieldbusses available. At the same time, it is very scalable making it suitable for both small and large systems/networks.

An operator / building manager can remote control the connected devices, including start/stop, change of operation mode, and settings. But a BACnet device also offers a variety of services, such as data transfer, scheduling, trending, alarming etc.
And the status messages, alarms, operation hours, energy consumption, etc. from the connected devices allow the building manager continually to optimise operation of the building.

BACnet is mainly used within the following building applications:
-Heating, Ventilation, Air conditioning (HVAC)
-Lighting control
-Security systems and fire alarm systems
-Elevator monitoring
-Pump control and monitoring
-Building Access control
-Energy supply monitoring

The BACnet Standard supports various physical media, which are the physical base of a network. This makes is usable for both high speed, expensive wiring as well as for low speed, low cost wiring