%0 Conference Paper %B Thermal Performance of the Exterior Envelope of Buildings V Conference Proceedings %D 1992 %T A New Method for Predicting the Solar Heat Gain of Complex Fenestration Systems %A Joseph H. Klems %A Jeffrey L. Warner %X

A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bi-directional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient.

The method has been applied to one of the most optically complex systems in common use, a venetian blind in combination with multiple glazings. A comparison between the scanner-based calculation method and direct system calorimetric measurements made on the LBL MoWiTT facility showed good agreement, and is a significant validation of the method accuracy and feasibility.

%B Thermal Performance of the Exterior Envelope of Buildings V Conference Proceedings %C Clearwater Beach, FL %8 12/1992 %G eng %L LBL-32198 %1

Windows and Daylighting Group

%2 LBL-32198