I. Introduction
Heating, ventilation, and air-conditioning (HVAC) system accounts for 40%–50% of energy use in buildings for providing occupant comfort [1], [2]. Whereas a large group is still not actually feeling comfortable staying inside [3]. This negative situation is substantially attributed to the insensible operation of HVAC systems, such as settled ON–OFF switch and fixed thermostat settings, and so on. Fortunately, the advances of information and communication technology (ICT) including smart sensing, data storing, and processing technologies are likely to turn it around [4]. Advanced HVAC control is expected for energy-efficient buildings, i.e., reduce energy use (cost) while simultaneously enhancing human comfort [5], [6].