Electrochromic glazing: environmental sustainability and comfort

Solar control in buildings is a major issue both in the heating and the cooling season. As the convective heat losses as well as the thermal energy required for ventilation is being reduced, the ratio of the internal heat and the solar irradiation is increased. The requirements in the heating season and in the cooling, season are different, in fact just the opposite. They called solar gain and internal gain in the heating season as opposed to solar load and internal load in the cooling season. Therefore, fixed solar control devices (e.g., overhang) are not suitable, especially not suitable in case of low energy buildings since they have a limited effect for solar control. What is a proper solution for solar control is a moveable shading device outside of the glazing. However, the external mechanical moveable shields are exposed to wind and other extreme weather condition and might get stuck or even break. Regular maintenance is required. This is a problem, especially in case of high-rise buildings. Electrochromic glazing changes the transmittance properties as electric voltage are applied to the terminals. The solar transmittance can be changed from very little to very high value providing the optimal transmittance for any circumstances without any moving mechanical parts. The operation can be controlled by a computer program, but the user has the option to override it temporarily. Applying electrochromic glazing has some additional advantage, e.g., better thermal and visual comfort. The paper introduces the tests made at the University of Cagliari using two test cabins, one fitted with normal, the other with electrochromic glazing. Comfort testing including a thermal manikin is a common task of the research groups at the University of Cagliari and that of the University of Pécs.