Proportions of direct and indirect indoor lighting — The effect on health, well-being and cognitive performance of office workers

Abstract

Indirect lighting has been recommended as a way to accommodate lighting needs in offices. To investigate this recommendation, the effect of four ceiling-mounted lighting schemes providing inverse proportions of direct and indirect lighting were studied in ordinary office environments. The study used a 4×3 mixed randomised-repeated design. Dependent variables assessed subjective symptoms, subjective well-being and cognitive performance. Glare, a major contributor to visual strain was physically removed. Photometric measurements showed that proportions of direct and indirect lighting affect the luminous environment. Except for an association between reduced job stress severity and direct lighting, the results indicate that proportions of indirect and direct lighting do not affect the dependent variables. A main effect of the new lighting installation was revealed for subjective symptoms and cognitive performance.