%0 Journal Article
%A Mark Spitzglas
%B IEEE/IAS 1984 Annual Meeting
%C Chicago, IL
%D 1984
%G eng
%T Defining Daylighting From Windows in Terms of Candlepower Distribution Curves
%1 <p>Windows and Daylighting Group</p>
%2 LBL-18087
%8 06/1984
%X <p>This work describes a method for evaluating quantitatively the daylight admittance of windows under any outdoor conditions in terms that make it possible to calculate interior light distribution. The work is based on a new concept in quantitative daylight analysis, the Transmission Function Approach, developed by the author while preparing graduate thesis (1976 and 1982) [2], [3], and [4].</p><p>The visible daylight flux introduced through a window (or other daylight-admitting aperture) can be considered, from the point of view of the internal space, as being emitted from a point source or from a finite-area uniform source. The photometric properties of those light sources are defined in terms of the well-known candlepower distribution curves. The ways in which this approach can be applied for different window designs are demonstrated.</p><p>This approach to the photometric properties of window systems allows one to translate typical daylighting calculation problems into a format in which they can be resolved using traditional electric lighting calculations or computer codes. Even daylighted-oriented computer codes are limited as to the geometric complexity of the windows they can model--this method eliminates such limitations. It will also contribute to a better understanding and visualization of the photometric properties of various windows and other daylight-admitting elements. This approach, therefore, may also serve as an educational tool.</p>