A method of controlling an orifice of a valve in an HVAC system to regulate a flow of a primary fluid through a primary side of a thermal energy exchanger of the HVAC system and thereby adjust a thermal energy transfer by the thermal energy exchanger from the primary fluid to a secondary fluid, flowing through a secondary side of the thermal energy exchanger, includes adjusting, by one or more electronic circuits, the orifice of the valve by applying an efficiency control algorithm to a control setpoint for the valve, the efficiency control algorithm processing the control setpoint for the valve to maintain energy-efficient thermal energy transfer. The method further includes the one or more electronic circuits determining the control setpoint for the valve, using current performance values of the HVAC system and recorded historical data of the HVAC system.

Current approaches for minimizing energy requirement of buildings are not designed to handle multi-input multi-output systems, such as electric vehicle-heating, ventilation, and air conditioning (EV-HVAC) system. Further, scalability of the solutions is another challenge. Present disclosure provides method and system for jointly controlling EV-HVAC system of a building. The system utilizes the potential of electric vehicle (EVs) in building energy management by treating EVs as buffers with random availability. The system performs EV-HVAC joint control that scales seamlessly with increasing EVs while respecting both thermal constraints of HVAC and state of charge (SoC) constraints of EV users.