Evaluation of angular dependence of spectral reflectance and transmittance of glazing systems for improving energy efficiency in buildings

Dynamic simulation has become an essential tool for energy and daylighting simulations in buildings. However, worldwide researchers highlight the discrepancies between simulated and real performance in buildings. An important limitation is that most databases used in simulation softwares only include measurements of diffuse reflectance and transmittance of glazing systems with directional-normal incidence. In this work, a methodology for measuring spectral reflectance and transmittance for different angles of incidence of glazing systems has been developed, and the measurements on a broad set of representative samples, for the spectral range 380 nm - 2500 nm with 5 nm resolution and for angles of incidence from 0 to 70 in steps of 5 , have been made publicly available. A simple physics-based model has been proposed, which fits the measurement results with a standard error of the estimate (SSE) below 0.01 in most cases, and a method to apply a principal components analysis (PCA) to the measurement data has been presented, which allows to reduce the amount of data up to 4 times while keeping the relevant information. The results of this work aim to enable more reliable energy simulations to improve the energy efficiency of buildings. • Assuming angle-independent optical properties of glazing limits simulations accuracy. • Glazing samples are characterized for angular-dependent reflectance and transmittance. • Measurement guidelines for angular optical properties of glazing are provided. • A two-parameter model reproduces the angular variation of optical properties. • PCA reduces data dimensionality and enhances interoperability.