%0 Conference Paper
%A Joseph H Klems
%A Jeffrey L Warner
%B Thermal Performance of the Exterior Envelope of Buildings V Conference Proceedings
%C Clearwater Beach, FL
%D 1992
%G eng
%L LBL-32198
%T A New Method for Predicting the Solar Heat Gain of Complex Fenestration Systems
%1 <p>Windows and Daylighting Group</p>
%2 LBL-32198
%8 12/1992
%X <p>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.</p><p>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.</p>