Self-Report Diary: A Method to Measure Use of Office Lighting

This methodological study was conducted to examine the suitability and reliability of the diary form to measure lighting use in work places. The occupants of 18 single-occupant offices were asked to report in diary form on their lighting-use-related activities and times present in their offices for one workday every two months from June 2009 through May 2010. Electronic measurement of the occupants' time in their offices and use of ceiling luminaires was recorded by data logger during the same period. The self-reported data correlated significantly with the logged data for the occupants' for the two variables investigated: (i) regulating of ceiling luminaires, and (ii) occupancy of their offices. The correlation was strongly significant between self-reported-and logged data with regard to light-on time, while a weak relationship was identified between the self-reported-and logged data regarding occupancy time. Considering the relationship between light-on time and occupancy time, a significant relationship from the self-reported data was found, but, unlike the logged data, these two variables did not seem to relate to each other. The results suggest that the diary form is suitable to measure office occupants' use of general lighting (ceiling luminaires), particularly for a short-term use, whereas the suitability to measure presence in offices is questionable. The diary form was also able to characterize the amount of energy used for lighting. However, the form should be improved to obtain more accurate responses and to indicate the lighting levels provided by dimming controls.