Advanced passive technologies for double-glazed windows daylight and solar control and their performance investigation: A review

Window, as a part of building envelope, can always provide outside visual for indoor occupants and effectively impact the indoor daylight and thermal environment and occupants’ health. Over the past decades, the demand for optimal indoor environments has been steadily increasing. In response to this need, several technologies integrated within conventional double-glazed (DG) systems for solar energy and daylight regulation were developed and investigated. This paper aims to comprehensively review the daylight, solar control of existing advanced passive technologies of DG windows for further building energy consumption reduction, focussing on Transparent Insulation Materials (TIM) and adaptive passive thermotropic (TT) materials. From the review of current studies, it can be concluded that, the traditional smart thermotropic DG window can effectively control glazing spectral response to prevent indoor occupants from over-illuminated and daylight glare, however, occupants’ view communication with the external environment was totally blocked when the TT material was in its translucent state. Meanwhile, TIM window systems can improve the indoor daylight and thermal comfort, but they also have some limitations, for example, they have fixed visible light and solar optical properties. As a result, a DG window integrated with TIM may allow less solar heat and visible light to be transmitted into a building space, which may lead to a lower cooling energy demand in summer but a higher heating energy consumption in winter and also a higher electric lighting requirement. To effectively avoid the disadvantages brought by windows integrated with single TT or TIM system, TT-TIM-coupled window system is recommended to further improve the passive daylight and solar control technologies in the future.