Putting the ceiling center stage: The impact of direct/indirect lighting on room appraisal

Abstract Luminaires that employ both a direct and indirect lighting component have the potential to optimally benefit both the visual and non-visual aspects in lighting designs. This type of luminaire, however, still spans a huge range of possible implementations with variations in the ratio of direct/indirect light and in the distribution of the light across the ceiling, all with their respective benefits and downsides. However, the effects of all these variations on for example preference and general appreciation are not well known. In the current study, we investigated the ratio of direct/indirect light and of lighting distribution on the ceiling in an open-plan office setting while keeping work-plane illuminance constant, and measured their impact on room appraisal, atmosphere, and visual comfort. In general, more indirect light and a more uniform ceiling distribution were appreciated, but not for all participants to the same extent. Participants could be classified into two main groups, where in the first group higher perceived brightness corresponded with more positive appraisals and comfort – this group responded well to more indirect light and more uniform distribution – whereas the second group appeared to dislike a bright environment and was less sensitive to ratio and virtually insensitive to uniformity manipulations.