Determining window size for view quality and building energy efficiency

Windows are critical in connecting indoor occupants with the outdoors. However, they influence building energy use, creating a design tradeoff. This study expands on previous research on window view access by including a wider variety of view contents, greater viewing distances, and associated energy implications. Using immersive Virtual Reality, 60 participants evaluated 80 office scenes that varied in window size, viewing distance, direction, and content. Results showed that view content, direction and its interaction with distance significantly affected satisfaction. Three-layered views or views with nature yielded higher ratings, whereas building-only or sky-building views scored lower. By combining this dataset with prior participant responses (n = 100), we refined the View Access Index and validated key thresholds: a window-to-wall ratio (WWR) of 25% is sufficient for direct views with high-quality content and approximately 40% with lower-quality content. This can lead to an approximately 8% difference in overall building EUI based on energy simulations across three U.S. climate zones. In contrast, side views with lower-quality content require up to an 80% WWR depending viewing distance, which can incur substantial penalties in extreme climates. A 45% WWR has a minimal energy impact and a WWR of 50% results in small to moderate increases compared to typical energy-efficient ranges (i.e., offices with a WWR 30–40%). Beyond a 50% WWR, designers should consider passive cooling measures (e.g., solar shading). These findings provide empirically based guidance for integrating human-centric and energy-efficiency considerations into early-stage window design.