This work describes a method forsevaluating quantitatively the daylight admittance ofswindows under any outdoor conditions in terms thatsmake 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], ands[4].

The visible daylight flux introduced through aswindow (or other daylight-admitting aperture) can besconsidered, from the point of view of the internalsspace, as being emitted from a point source or from asfinite-area uniform source. The photometric properties of those light sources are defined in terms of the well-known candlepower distribution curves. Thesways in which this approach can be applied for different window designs are demonstrated.

This approach to the photometric properties ofswindow 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. Evensdaylighted-oriented computer codes are limited assto the geometric complexity of the windows they cansmodel--this method eliminates such limitations. Itswill also contribute to a better understanding andsvisualization of the photometric properties of variousswindows and other daylight-admitting elements.sThis approach, therefore, may also serve as an educational tool.

CY - Chicago, IL U1 -Windows and Daylighting Group

U2 - LBL-18087 ER -