Architectural Glass Solar and Thermal Control Coating Technologies

Building fenestration, of which glass constitutes a crucial component, is often considered a weak link in the building envelope due to its low thermal resistance and static solar transmittance. Hence, modern glazing technologies aim to optimize thermal and optical performance to improve building energy efficiency and occupant comfort. In particular, coatings have emerged as promising means to transform windows from energy liabilities to assets through radiation control. In this chapter, several coating technologies with static and dynamic optical properties are discussed, and new material developments are presented. The review indicates that static and dynamic technologies are often complementary in enhancing glazing performance. Low-emissivity coatings effectively reduce thermal gains and losses, while solar control coatings exhibit superior performance in reflecting near and far infrared radiation. To further improve heating performance, electrothermal coatings actively enhance glazing thermal resistance by Joule-heating, while photothermal coatings achieve this passively through absorption and efficient conversion of ultraviolet and near-infrared radiation into heat directed inwards. Additionally, photothermal coatings can be utilized for absorption-based solar control by emitting heat outwards. To further enhance the cooling performance, dynamic coatings can modulate the transmission of solar radiation by switching between solar transmitting and blocking states in response to external stimuli. Active dynamic coatings, including electrochromic and gasochromic, offer superior modulation abilities but are hindered by high fabrication and building-integration costs and the need to develop effective operational strategies. In contrast, photochromic and thermochromic coatings are more accessible passive technologies that shift the focus to optimizing intrinsic material properties. Selecting a suitable coating technology depends on various factors, including building use, location, climatic conditions, window-wall ratio, orientation, and ultimately payback periods. Nevertheless, multi-functional coatings that combine low-emissive, dynamic solar modulation, and anti-reflective properties are particularly promising for high-performance advanced glazing applications.