This study investigates how building occupant evaluations differ from actual physical building conditions, with an analytical focus on 'sustainability' and 'behavioural environment'. Behavioural environment, as an integrated concept of physical environment and the interactions between a person and the physical environment, can be used as mediation between physical environment and occupants. Particularly given that sustainability can be entirely achieved by occupant behavioural change, not just through the use of green technologies, a better understanding of behavioural environment could help determine what design strategies or technologies can be effective in encouraging occupant behavioural change. By analysing both objective and subjective data collected from Korean office workers (N=341) in nine office buildings, a few correlations were found between physical environment and building occupants. Surprisingly, people are unlikely to perceive controls over the environment in accordance with the existence of the actual control. The implication is that building occupants are not always aware of the presence of controls or they may think that the control equipment is for service personnel only. Thus, training in the use of controls must be accompanied by the provision of controls, in order to achieve both energy savings and comfortable environments.