A PRACTICAL CALCULATION METHOD SOLAR SHADING PERFORMANCE CHANGES FOR CONVENTIONAL WINDOWS

This paper proposed a practical calculation method of the solar shading performance changes for conventional windows with inner blinds or with blinds between panes. The solar shading performance indices such as the solar heat gain coefficient (SHGC) and the transmittance change depending on the profile angle as well as the solar incidence angle. In the proposed method, the solar radiation is split into two portions. One is the portion that transmits through the gaps between slats the other reaches slat surfaces. The transmittance and the inward heat flow of absorbed radiation into window components are calculated for each portion. The transmittance and the SHGC can be estimated with adequate accuracy and the proposed method is sufficiently practical to apply for building energy simulation programs.