Building performance of thermochromic glazing

Thermochromic switchable glazing has been gaining increasing popularity as a dynamic building envelope solution aimed at reducing energy demand in buildings, and specifically cooling energy needs, due to its capability of varying optical properties according to the material temperature. To date, different thermochromic glazing technologies are being researched, developed, or commercialized, with different ranges of varying optical properties, optical behavior (specular or light scattering attitude), and temperature dependence. The integration of thermochromic glazing in buildings enables management of the solar loads, responsible for energy needs for heating, cooling, and lighting as well as affecting the visual and thermal comfort conditions of building occupants, without any need for an active control. Therefore, quantifying the whole building performance of thermochromic glazing requires a comprehensive evaluation considering different physical domains simultaneously (i.e., energy use, daylight comfort, thermal comfort, etc.). Towards this aim, integrated building performance simulation methodologies can be used in the design phase of the building/material. In this chapter an overview of thermochromic transparent materials is presented, together with a critical analysis of their features and main applications. Consequently, a review of available thermochromic glazing products is provided, considering their thermo-optical properties and technological integration. Finally, a quantitative evaluation of their whole building performance regarding total energy use and visual comfort aspects is discussed for a typical sun-oriented office building in three different climates (heating dominated, temperate, and cooling dominated), in order to provide an overview of their potential performance improvements, as compared to traditional static glazing technologies.