A building emulator for use in HVAC control applications consists of a detailed real-time simulation of the building and HVAC plant, including the sensors and actuators, connected to a real-time energy management and control system, including direct digital controllers. Addresses the design, selection and configuration of the hardware and software for building emulators. Different architectures are illustrated by descriptions of emulators developed by participants in an international collaborative research project. A procedure for setting up and testing building emulators is discussed, and the effect of communication time-step on different aspects of their performance is discussed.KEYWORDS: commissioning, designing, construction, emulation, energy management, controls, calculating, testing.