The relationship between wall reflectance and daylight factor in real rooms

To reduce lighting loads and meet targets set in building codes, architects are encouraged to make maximum use of high-reflectance colours for internal surfaces. Although in theory improving daylight factors and reducing electricity consumption of lighting circuits, this can constrain choice and may conflict with aesthetic desires. In this article, we examine the relationship between changes in surface albedo and changes in daylight factor for typical non-domestic spaces. The issue is tackled using both an analytical approach and commercial ray-tracing software such as that used by engineers for designing lighting layouts (Radiance). Unlike in design work and previous theoretical work, the fraction of surface obscured by items such as pin boards is accounted for, with the extent of such areas estimated from surveys of buildings. It is found that, within sensible bounds, changes in wall albedo have little impact on daylight factor.