Multiple regression statistical methods are used in the analysis of fenestration effects an space conditioning requirements of commercial buildings. The procedure permits the quantification of changes in energy usage due to certain factors that influence the selection of fenestration, namely, the basic window properties of size, conductance, and shading coefficient. In addition, the usefulness of daylighting and overhangs was examined. A representative range of climatic zones, orientations, and installed lighting power, in addition to the primary parametric on glazing properties (area, U-value, shading coefficient), were considered during the course of the study. The DOE-2.1B energy analysis simulation program was used to define the thermal response of a prototypical building module, which was used to create a data base for the regression analysis.