Thermochromic smart window technologies for building application: A review

Thermochromic window technologies promise pioneering architectural windows with energy-saving capabilities through the intelligent regulation of indoor solar irradiation and modulation of window optical properties in response to real-time temperature. Thermochromic glazing has been thoroughly advanced from a materials perspective, with many kinds of thermochromic coating techniques developed thus far, however, a far smaller body of work exists to investigate how these kinds of glazing would perform within buildings. This paper presents a systematic review of these thermochromic films, coatings and glazings that have been used to analyse primarily energy saving capability in buildings, using computer simulation as well as full-scale models. Research from 2009 to 2019 was obtained from architecture and engineering databases, identifying window types modelled, energy savings found, and comfort analyses conducted. Thermochromic windows were reported to have the potential to save heating and cooling energy demand from 5.0 to 84.7%, in comparison to plain glass and dependent on climatic conditions. Differences in energy saving capability were analysed based on location and glazing type. Thermochromic window energy performance was found to vary significantly between different cities using the same film type (up to 73.4%), but far less so between different films types used in the same city (up to 21.6%). Few studies were shown to have explored thermochromic windows from a visual and thermal comfort performance perspective. This paper highlights areas of guidance for future studies of thermochromic glazing for energy-efficient building applications to better forecast energy saving performance of thermochromic windows for real building application.