Determining Off-Normal Solar Optical Properties of Insect Screens

Abstract

Shading attachments may have a strong influence on solar gain. The determination of off-normal solar optical properties of individual layers of glazing/shading systems is required in order to estimate this solar gain, which influences building peak load and annual energy consumption. Recently, a unique test method was developed for the experimental determination of off-normal solar optical properties of flat shading devices (e.g., drapery fabrics and roller blinds). The study described in this research applies the same method to insect screens. More specifically, semi-empirical models were developed from measured data, obtained at varying angles of incidence using an integrating sphere installed in a spectrophotometer. The measurements were taken on six samples of screen material with various mesh sizes and wire reflectances. The measured data were compared with analytical models recently developed from geometry and ray tracing techniques. The results of this study demonstrate the reliability of using special sample holders attached to an integrating sphere to obtain off-normal solar optical properties of flat shading materials.