Suspended particle device windows in residential buildings: Measurement-based assessment of comfort and energy performance for optimal control during intermediate and heating seasons

Smart windows effectively reduce cooling loads by controlling the visible light transmittance (VT) and solar heat gain coefficient (SHGC), and several previous studies have focused primarily on the analysis of comfort and cooling energy performance attributable to smart windows during the summer. However, understanding the annual effects of changes in the VT and SHGC of smart windows on indoor visual and thermal environments is crucial since windows impact the comfort and energy performance of buildings throughout the year. Therefore, this study comprehensively evaluates the performance of suspended particle device (SPD) smart windows during intermediate and heating seasons because insufficient research has been conducted. The experimental residential building is located in Sejong city, Republic of Korea (36.5°N latitude, 127.3°E longitude) and is characterized by a temperate climate zone. Measurements from September to December 2023 assessed glare, indoor daylight illuminance, thermal comfort, and heating and lighting energy under various sky conditions and smart window control methods. Considering the results of the measurements comprehensively, this study recommends the following operational strategies: during intermediate periods, an “always transparent state” should be employed on cloudy days, and “automatic control” based on the indoor illuminance levels should be employed on clear days. During heating periods, an “always transparent state” should be adopted on cloudy days, and “automatic control” should be adopted on the basis of glare occurrence on clear days.