A Comparison Between Calculated and Measured SHGC for Complex Fenestration Systems

Calorimetric measurements of dynamic net heat flow through a complex fenestration system consisting of a buff venetian blind inside clear double glazing are used to derive the direction-dependent beam SHGC (solar heat gain coefficient) of the fenestration. The data are compared with calculations according to a proposed general method for deriving complex fenestration system SHGC`s from bidirectional layer optical properties and generic calorimetric properties. Previously published optical data for the same venetian blind and generic inward-flowing fraction measurements are used in the calculation. Satisfactory agreement is found between SHGC measurements and calculation. Significant dependence on incident angle was found in the measured SHGC`s. Profile angle was not found to be a useful variable in characterizing the system performance. Predicted SHGC was found to be inherently dependent on two angles, although only the incident angle variations were observable under test conditions.