I wouldn't call it automation per se. HVAC control is simply named... well, control.
The last control company I worked for was heavily invested in the Delta controls' products. (All working on top of the BACnet protocol) Last I heard Delta also started to toy with Zigbee.
In my head there aren't mutually exclusive, as the BACnet architecture enables it to be built on top of other protocols. (BACnet/arcnet, BACnet/MSTP, BACnet/Ethernet, BACnet/IP...)
The last control company I worked for was heavily invested in the Delta controls' products. (All working on top of the BACnet protocol) Last I heard Delta also started to toy with Zigbee.
In my head there aren't mutually exclusive, as the BACnet architecture enables it to be built on top of other protocols. (BACnet/arcnet, BACnet/MSTP, BACnet/Ethernet, BACnet/IP...)