Mixed-mode ventilation combines natural ventilation and mechanical ventilation to improve building energy efficiency and indoor air quality. However, in practice, mixed-mode ventilation buildings do not always achieve better performance than mechanically ventilated buildings, largely due to inappropriate window operations. Therefore, the sequences of operation for terminal devices serving zones with operable windows should be designed in recognition of these risks, which in turn should be informed by research investigating occupants' window and thermostat use behaviour. This research analyzes window and thermostat use data collected from two mixed-mode ventilation buildings in Ottawa, Canada. Based on this analysis, the control algorithms are developed, and 3-16% of energy reductions could be achieved based on building performance simulation (BPS). It is also found that the unregulated window operations could increase the heating load up to 21% and cooling load by 33% relative to identical buildings with fixed windows in a cold climate.