Abstract: Heating, cooling, and ventilation equipment in a building may be controlled to improve building performance and/or occupant comfort. For a building, such as a low-load building, with multiple sub-systems of an overall HVAC system that can be actuated to impact indoor environmental conditions, an operational mode used to control such HVAC equipment may be selected. The selection may be based on input data from sensors, including indoor and outdoor environmental conditions, and occupancy level in combination with multiple models. Data collected over time may be used to form multiple types of models, including predictive models of building performance, future indoor conditions, and occupancy levels, and/or energy usage. The models may be used to select a control strategy. Based on the selected strategy and user preferences, a set of rules may be applied to generate control signals that control operation of HVAC subsystems.