Evaluation of Spatial Brightness Variation in Office under Daylighting Control

In this study, the author estimates the hourly spatial brightness index in an office under daylighting control by Venetian blinds and examines new evaluation methods on the basis of annual variation in the values. A spatial brightness index (SB), which has been previously proposed by the author, is applied for the evaluations in this study. The 90% range of annual variation in SB values, which is the difference between the 95th percentile value and the 5th percentile value, is useful for comparing the in fl uence of daylighting control on the spatial brightness variation. Also, evaluating the 50th percentile value of them results in a suitable target illuminance level for electric light control in each daylighting condition. These results indicate that the evaluation methods in this study are useful for designing daylighting or lighting control so that it will lead to a comfortable condition, which means not too bright and not too dark.