Intelligent control strategies for heating, ventilating and air conditioning (HVAC) processes are studied by considering a single-zone air-handling unit (AHU) and a two-zone space-heating system (TZSHS). Temperature responses of the AHU with single and multiple input controls are given. Application of decentralized control to the TZSHS, with and without preview action, is described. The implementation of intelligent strategies such as variable cold-deck temperature and night setback are illustrated with examples.