While the role of occupants is deemed crucial in building energy use, little is known how they interact with the built environment to maintain comfort, especially in residential contexts. The study aims to better characterise occupant air-conditioning (AC) use decisions and comfort behaviours within households. Combining instrumental measurements and smartphone surveys, we monitored AC usage patterns, indoor and outdoor climatic factors, and environmental adjustment behaviours in Australian homes. Our field observations reveal the patterns of residential AC operation such as AC usage duration and trigger temperatures for space cooling/heating. The analysis on self-reported behaviour data derives statistical models to enable predicting of occurrence of environmental control behaviours including operation of AC, fans and windows, in relation to the external climate factor.