Office worker response to fluorescent lamps of different CCT and lumen output

This paper describes a field study concerning the effects of correlated color temperature (CCT) and lumen output of fluorescent lighting on office workers’ perceptions and visual comfort. Four luminous conditions were created and organized as a two by two factorial design, comprising two levels of CCT (that is, 3500 and 5000 K) and lumen output (that is, 2330 and ≈ 3000 lm). Participants experienced a baseline condition followed by the four treatment conditions and then returned to the baseline condition; each treatment lasted two weeks. Twenty-six participants adapted to the luminous conditions in the first week of each treatment period. In the second week they completed brief assessment surveys three times daily using smart phones. Participants completed a more comprehensive survey on the last day of each treatment period. CCT was found to be a significant factor affecting perceptions of brightness, visual comfort, and satisfaction of color temperature. There were interaction effects between CCT and lumen output and between CCT and the presence or absence of a window. The luminous conditions with higher CCT (that is, visually cooler) or higher lumen output were rated to be brighter than those with lower CCT (that is, visually warmer) or lower lumen output. Participants judged the luminous condition with both higher CCT and higher lumen output as being too bright. CCT was the only statistically significant factor for perceived visual comfort and the satisfaction of color temperature. The luminous conditions at 5000 K were regarded as less comfortable than those at 3500 K. 5000 K was judged to be too cool when the higher lumen output lamps were in place. For the participants with daylight in their office, 5000 K was especially judged to be too cool.