A key finding from field studies on manual lighting and blind control in single offices is, that even though occupants behave differently, they use their lighting and blind controls consciously and consistently. The consistency finding forms the theoretical basis for occupant behavior models such as the Lightswitch Model that is used by DAYSIM. Field studies have also found that there are certain basic behavior types which have been termed 'active' and 'passive'.
- Active users operates the electric lighting in relation to ambient daylight conditions, open the blinds in the morning, and partly close them to avoid visual discomfort. In DAYSIM there are two ways to predict when occupants experience visual discomfort. The difference is set under ANALYSIS>> 'User Requirements and Behavior'. A user either closes the blinds when direct sunlight above 50 Wm-2 is incident in the work plane sensors. The alternative is that a user closes the blinds when the daylight glare probability at the user's typical view point exceeds 40%. More details can be found here.
- Passive users keeps the electric lighting switched on throughout the working day and keeps the blinds lowered throughout the year.
Interpreting User Behavior Models
As explained above, Lightwitch provides two types of behavior for active and passive users. How can a modeler deal with the resulting uncertainty introduced in the simulation?
- Active equals design intention; passive equals design risk'. According to this thinking an active use of personal control is a use according to the original design intentions because this is why the control were provided to the user to begin with. As there is the possibility that a use is 'passive' with resulting potentially negative energy implications, the passive simulation is carried out to see how robust a building design is against users working against it.
- Mixed use. This (older) interpretation of the two behavior types foresees that both types of users will be equally distributed throughout the building. The simulation is hence run twice, once for each user type, and the resulting mean energy use is reported.