Energy performance and comfort analysis of three glazing materials with distinct thermochromic responses as roller shade alternative in cooling- and heating-dominated climates

Abstract

Thermochromic (TC) smart windows are a leading passive building design strategy. Vanadium dioxide (VO2), hydrogel and TC-Perovskite glazing, which constitute the main categories of TC materials, modulate different wavelength regions. Although numerous studies have reported on these TC glazings’ energy-saving potential individually, there is a lack of data comparing their energy efficiencies. Moreover, their suitability as an alternative to dynamic solar shading mechanisms remains unexplored. Using building energy simulation, this study found that a hydrogel glazing with broadband thermochromism can save more energy (22–24% savings on average) than opaque roller shades (19–20%) in a typical office in both New York and Hong Kong. VO2 glazing performed comparably to translucent roller shades (14–16% savings), except when used in poorly daylit conditions. TC-Perovskite was a poor replacement for roller shades (~2% savings). The window-to-wall ratio (WWR) that allowed both energy savings and optimal natural light penetration was also identified for each glazing. Hydrogel glazing demonstrated both energy and daylight efficiency in Hong Kong’s cooling-dominated climate when used in 40–50% WWR configurations. In New York’s colder conditions, VO2 glazing did so for higher WWRs (50–70%). Roller shades could also achieve simultaneous energy savings and visual comfort, but only for highly glazed facades (up to 80%).