A Study on the Subjective Response for Corrected Colour Temperature Conditions in a Specific Space

The luminous environment in a space is one of the key factors affecting the occupants' work performance and mood. An illuminance value is quantitatively standardised and recommended for a specific space, but correlated colour temperature (CCT) is not. Although some studies on CCT conditions have shown that higher CCT conditions appear brighter to people than lower CCT conditions, other studies have indicated that there is no relationship between brightness perception and CCT conditions. This paper reports the results of two subjective evaluations of different CCTs on personal preferences: brightness perception, subjective impression and work performance; and describes suitable CCT conditions for a specific space and activities. One subjective evaluation (field test) was performed with four different CCT fluorescent lamps in an office space, and another (photo-image test) was performed with pictures under four different CCT conditions in an office, living room and bedroom. The results were statistically analysed for gender, preferred CCT, suitable CCT of each space and brightness sensitivity. The results showed that people preferred different CCT due to the purpose of a space, and different CCT conditions for specific activities performed in that space. The study suggests that changeable CCT lightings are better than fixed CCT for occupants in a space.