In-situ Evaluation of High-Performance Glazing Based on Illuminance and Glare

Abstract High-technology glazing panes are designed to meet the need for natural light, while optimizing key functions such as reducing solar heat gain in spaces and/or redirecting daylight to the rear of the spaces. However, the actual performance in terms of both illumination and glare protection of these glazing systems is often unknown. This study aims to compare the visual comfort performance of four complex fenestration systems by means of point-in-time measurements under real sky conditions and for different seasons. The tested systems included: two glazing types with embedded seasonal solar protection, namely, MicroShade™ and Coolshade™, one prototype of daylight redirecting glazing with embedded micro-mirrors (GEMM), and one clear glazing. We conducted our tests in side-by-side nearly identical spaces in the NEST building in Dübendorf, Switzerland. Results showed a higher daylight provision for clear and daylight redirecting glazing. Discomfort glare assessment from daylight showed that MicroShade™ was substantially more efficient at addressing glare due to sunlight for high sun angles when compared to Coolshade™. The performance of the GEMM prototype was highly dependent on the glazing pane used and one pane provided a promising performance when it comes to mitigating glare risks for high sun positions. However, none of the systems were able to provide an adequate glare protection for lower sun positions. The performed measurements provide a basis for the calibration of simulation models.