States that computer vision is an approach that understands the object or the scene and its three-dimensional properties from one or a sequence of images of a moving or stationary object or scene, taken by monocular or polyocular moving or stationary observers. Describes the application of computer vision to assist the conventional PID control for HVAC systems. Explains how, by adopting a computer vision that can estimate the number of residents within an air conditioned space, it is possible to identify any abrupt changes within seconds, to which conventional transducers are in no way comparable. Shows by a computer simulation that there are significant improvements with respect to both response rate and energy saving. Describes the hardware and software developments associated with the computer vision system and two modes of HVAC control - step control and human tracking.KEYWORDS: year 1995, Heating, ventilation, air conditioning, computers, vision, cameras, controls, calculating