Thesis (M.S., Mechanical Engineering) -- University of Idaho, 2016 | Computer energy models were developed for controller-in-the loop co-simulation using the EnergyPlus software and the Building Controls Virtual Testbed. Models were constructed to approximate building envelopes and mechanical systems. The models simulated typical inputs expected by building controllers and desired output signals were communicated back into EnergyPlus at set simulation time increments. This research extends previous work which demonstrated control of economizing function of an air handling unit by investigating control of additional functions including supply air temperature control. By adjusting the supply air temperature modulation range according to techniques described in this paper it is estimated that up to 124 MWh (7%) savings in total facility energy would be realized. Additional research was performed into virtual control of multiple air handling units and multiple controllers-in-the-loop. The challenge of programming controllers for constant air volume units with no zone reheat terminals is examined. Reduction of hours of unmet heating setpoint during occupied times as well as e?ects on system energy usage are realized. E?ects of adjusting system performance towards minimizing unmet hours may result in up to a 30% increase in energy use. Suitability of energy modeling and co-simulation for pre-commissioning building automation and control systems is discussed.