Enhancing Year-Round Thermal Comfort with Solar Control Films: A Solar-Adjusted and Spatial Assessment Considering Adaptive Clothing Behavior

Abstract

Windows significantly contribute to thermal discomfort in high solar irradiance climates by allowing excessive heat gains and uneven indoor temperatures. This study introduces a solar-adjusted analytical framework for evaluating year-round indoor thermal comfort, integrating dynamic shortwave solar radiation effects, spatial zoning, and occupant behavior into comfort assessments. The methodology employs the Predicted Mean Vote adjusted via the SolarCal model and long-term comfort metrics to evaluate the effectiveness of Solar Control Films (SCFs) across twelve orientations at 30º intervals, in a cold arid (BWk) climate. Results demonstrate that absorbing SCFs with solar transmittance values between 0.22 and 0.40 reduce heat-related discomfort by 70–90% on average across all orientations, while the reflective film completely eliminates heat-related discomfort under all studied conditions. Although SCFs increase cold discomfort hours, the overall impact remains beneficial. Integrating hourly clothing adjustments into the framework reduces predicted warm discomfort by more than half and cold discomfort by 28% on average, offering a more realistic evaluation of occupant experience. Importantly, the choice of metric influences performance rankings: for average Thermal Comfort Availability (TCAmean), the reflective film excels in north, northwest, and west orientations, while absorbing films perform best in east and northeast. For time Thermal Comfort Usability (tTCU10-90), the reflective film outperforms other options across most orientations, doubling hours with 90% of the space in comfort conditions in north and northeast orientations, where heat discomfort is most critical. SCFs also reduce overheating near windows and homogenize thermal comfort across spaces, enabling optimized HVAC operation. This work highlights the potential of integrating solar radiation impacts and dynamic, spatially resolved metrics into thermal comfort assessments, providing insights for retrofitting strategies and climate-responsive design.