Dynamic simulation of conventional and smart glazing systems: derivation and integration of a temperature-dependent solar factor model

Smart glazing technologies present a promising strategy for enhancing the energy performance of buildings through dynamic regulation of solar heat gain. Among these, thermochromic glazing enables passive, temperature-dependent modulation of solar transmission; however, modelling its hysteretic behaviour in building energy simulations remains challenging. The present study proposes a novel, computationally efficient model of the temperature-dependent solar heat gain factor of thermochromic glazing. The model is based on hysteresis and is capable of capturing both heating and cooling transitions with minimal numerical complexity. The model is integrated into a dynamic thermal simulation framework to evaluate indoor air temperature under representative winter and summer conditions in Fez, Morocco. A preliminary parametric analysis was conducted to isolate the individual effects of solar heat gain factor and thermal transmittance (U-value) on indoor thermal behaviour. The performance of commercially available smart glazing systems and innovative VO2-based thermochromic glazing is then evaluated. The findings indicate that summer performance is primarily governed by solar modulation capacity, whereas winter behaviour is more sensitive to thermal transmittance. The integration of VO2-based smart glazing with enhanced thermal insulation effectively mitigates summer overheating while concurrently enhancing winter thermal stability. Incorporating hysteresis provides realistic seasonal behaviour without increasing model complexity.