Development and validation of an optical model for water-based windows with clear glazing: A parametric performance assessment

This paper presents a study of the optical performance of window systems with embedded water layers, here called water-based windows (WBWs). Spectrophotometer measurements were performed on four WBWs prototypes, in addition to a single and double-glazed window. A numerical model was also developed to calculate the optical performance of multilayer WBWs, which was validated by laboratory measurement results. Furthermore, a parametric performance assessment of multilayer WBWs is caried out for windows using only clear glazing and layers of water and air. The results corroborate previous studies that the use of water in glazing ensures higher visible light transmittance (Tvis) values while it reduces solar transmittance (Tsol) rates compared to the same glazing without water. Increasing the thickness of a water layer in a WBW does not interfere in Tvis values, but decreases direct solar gain. Increasing the number of "glass-water" interfaces on a WBW has little impact on its optical performance. On the other hand, more interfaces of "glass-air" increases the glazing reflectance and reduces both Tsol and Tvis values. Therefore, different combinations of air, water and glass layers in a WBW can result in very different optical performance results. Last but not least, the optical performance of WBWs when varying the angle of solar incidence (aoi) showed the same pattern compared to single or multi glazing with air.