What is BACnet?

BACnet is the Building Automation and Controls NETwork, an open protocol standard that has revolutionised building services controls since the mid-1990s.

The protocol makes it possible for computerised building automation devices to exchange information about heating, ventilation, and air conditioning control (HVAC), lighting control, access control, fire detection systems and their associated equipment.

It was developed by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), and is now a national standard in more than 30 countries as well as being an ISO global standard.

BACnet provides a standard way of representing the functions of any device made by any manufacturer.
http://www.bacnet.org