The newly developed building energy management system (BEMS) is presented. The main feature of the BEMS is the following 2 technologies. (1) The new air-conditioning control technology for the energy saving of buildings. The method is mainly focused on the compatibility of energy savings and comfort. The energy saving is achieved through the twin coil air handling unit that controls room humidity and temperature independently without energy loss and by the optimal operation of HVAC (Heating, Ventilating and air-conditioning) system, manipulating the supplying airflow temperature to the rooms, room temperature and the humidity. The comfort is kept by the index (PMV: Predicted Mean Vote) that is calculated with room temperature, humidity, radiation temperature, wind velocity and so on. In order to avoid large-scale nonlinear programming for optimal conditions, the driving function is introduced. The effectiveness of the HVAC control technology is proved through a building HVAC data and the simulations using the data. (2) Automated demand responding mechanism. The mechanism has function that predicts how much electricity demand is trimmed for a given reward. It also has ability to communicate with community energy management server for finding appropriate balances between electricity demand and generations.