Energy-Saving Potential of Thermochromic Glazing in a Cold Climate

Windows are considered the least-efficient components in the thermal envelope driven by their low thermal resistance and static transmittance to solar gains. Thermochromic coatings are promising to address the latter. Nevertheless, current building energy simulation (BES) tools were not originally developed for the performance assessment of adaptive facades. Hence, in this paper, a previously developed 1-D transient heat transfer model was utilized to evaluate the annual heating and cooling energy performance of two thermochromic glazing systems, including commercial Ligand-Exchange (LET) and industrial Vanadium Dioxide (VO2) thermochromic coatings, and compare their performance to reference low-E coated glazing in the cold climate of Toronto, ON. Contrary to current BES, the model accounts for spectral-selectivity, gradual transmittance change, hysteresis, and switching time of thermochromic coatings. A representative room’s annual energy performance was evaluated for different glazing configurations and several exposures. The results show that the VO2 thermochromic glazing is the most energy-efficient configuration in Toronto, driven by low solar transmittance and increased near-infrared reflectance at higher coating temperatures. Furthermore, increasing the switching time and hysteresis width have less significant effects for VO2 glazing.