Simulation model of a building HVAC (heating, ventilation, and air-conditioning) mechanical system plus HVAC controls, the building shell, the heating/cooling plant, and energy management and control system (EMCS) algorithms. The main program of HVACSIM+ (HVAC SIMulation PLUS other systems) employs a hierarchical, modular approach and advanced equation solving techniques to perform dynamic simulations of building/HVAC/control systems. The modular approach is based upon the methodology used in the TRNSYS program. A free copy of HVACSIM+ can beĀ downloaded from the NIST website.a