States that one of the most popular open communication protocols for building automation systems is the ANSI/ASHRAE Standard 135-1995: BACnet - A Data Communication Protocol for Building and Automation Control Networks. Reviews reasons for using an open protocol standard and specific reasons why BACnet works for the building automation industry. Goes on to describe projects that have been implemented using native BACnet controllers at every system level. These projects include integration of controllers from different manufacturers using BACnet as the communication protocol of choice.