A Simplified Procedure for Calculating the Effects of Daylight from Clear Skies

A simplified procedure is described for calculating daylight illumination at any point within a room under clear sky conditions, which is consistent with the CIE recommended daylight factor method. The calculation procedure used here separates the light reaching the point being considered into three components; (1) light directly from the sky, (2) light after reflection from external, and (3) internal surfaces. Graphs and tables are developed for these components in order to evolve a calculation procedure which is simple to apply rather than lengthy direct computation from first principles. Finally, a validation case study is presented in order to demonstrate the accuracy of the proposed calculation procedure and to give readers a direct reference for future use.