Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance

We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed

Measured performance of selective glazings

Measurements of the net heat flow through four selective glazings in comparison with clear double glazing under late summer outdoor conditions are presented. The SHGC for each glazing is extracted from the data and shown to be angle-dependent. The method of extracting the angle-dependent SHGC from the data is checked by comparing the measured SHGC for the clear double glazing to the calculation of OW 4. 1, which is assumed to be correct. Good agreement between the two is found. The measured angle-dependent SHGC`s of the selective glazings are then used to test the OW 4.1 selective glazing calculation and good agreement is again found