A new approach for specifying interoperable BACnet(r) building automation and control systems was recently approved by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The new approach, part of addendum D to ASHRAE/ANSI Standard 135-1995, BACnet -- A Data Communication Protocol for Building Automation and Control Networks, is based on the use of BACnet Interoperability Building Blocks (BIBBs). Each BIBB defines a small portion of BACnet functionality that is needed to perform a particular task, according to Steven Bushby, chairman of the ASHRAE BACnet committee.