Average daylight factor under various skies and external environments

The average daylight factor (DFave) method with the computation based on standard overcast sky conditions is a useful daylighting criterion. Recently, the International Commission on Illumination (CIE) has adopted a range of 15 standard sky distributions covering the whole spectrum of usual skies found in nature. In a dense urban region, the external environment plays a significant role in daylighting design. This paper studies an approach to calculating the DFave for rooms facing heavily obstructed environments under overcast and non-overcast skies. The performance of the proposed method was evaluated against the results obtained by computer simulations. The proposed approach provides a simple alternative for predicting indoor daylight illuminance, which is useful for glazing designs and building thermal analysis.