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Brotas, Luisa and Wilson, Mike (2008) The average total daylight factor. Light & Engineering, 16 (2). pp. 52-57. ISSN 0236-2945
Daylight calculations are usually based on uniform or overcast skies, but in areas where clear skies are predominant it may underestimate the illuminance levels and might lead to inappropriate urban and window design. In urban canyons reflected sunlight from obstructions and ground is a major contribution to the illumination of buildings in orientations and at times when the sun is behind the building. A simplified calculation that takes into consideration reflected sunlight may be used for quick calculations in the initial design stages of the project. This paper presents the average total daylight factor as a calculation for rooms in urban canyons under sunny climates. It is based on the principle of the integrating sphere and the ratio between the total vertical illuminance on the facade of an urban canyon and global horizontal illuminance. In a similar way to the daylight factor, a method based on the relation between the global horizontal to the total vertical illuminance allows for the sizing of the windows and can be used to evaluate how well a space is daylit under a clear sky.
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