Using adjustment to define preferred illuminances: do the results have any value?

The method of adjustment is examined as an approach to determine occupant illuminance preferences. From the results of previous studies using illuminance adjustment and recent studies performed purposely to investigate methodology, it is concluded that the method of adjustment has little value as a means of estimating the mean preferred illuminance. However, there is some evidence that when users are allowed to set their own light level that this enhances their satisfaction with the visual environment. Thus careful selection of the control variables (available range and initial value) offers the opportunity for reduced illuminances, and thus reduced energy consumption, whilst maintaining satisfaction.