Sky luminance measurements for design and control of indoor daylight illumination

Abstract

Cost-effective daylighting design and artificial lighting control require data on the daylight illuminance at the work station. The current definition of the daylight factor is not appropriate to convert accurately from the horizontal illuminance under an unobstructed sky to the actual illuminance in a room. The actual daylight illuminance of a room is found to be related to the actual luminance pattern of the sky in the direction of view of the window. To represent conveniently both the dynamic character of the sky luminance and the weight of the luminance patches in respect of the indoor illuminance, the dynamic equivalent luminance is introduced. Some progress has been made in predicting the indoor direct illuminance due to time-varying sky luminance patterns more accurately.