Computed indoor light conditions due to outdoor skyglow at night

Light pollution poses a significant challenge in the built environment, negatively impacting human health. One key aspect is light trespass, where light extends beyond its intended target, such as windows, causing annoyance, disrupted sleep patterns, and a diminished quality of life for residents. While shielded outdoor lighting can address direct light trespass, mitigating light trespass from skyglow presents complexities due to its unshieldable nature. This study explores the impact of skyglow-induced light trespass on indoor environments, aiming to develop a tool for quantifying its effects on human health in future studies. Using an innovative analytical approach, we simulated and measured skyglow within a specific built environment, considering window sizes and bed positions. Results indicate that room orientation, bed-window separation distance, and bed depth below the window significantly influence vertical diffuse illuminance. Surprisingly, the maximum illuminance occurs at a specific depth within the room, influenced by the interaction between window solid angle and sky segment brightness. Optimizing bedroom configurations can effectively minimize diffuse illuminance from skyglow, mitigating its negative impacts on human health. Importantly, this effect varies significantly when transitioning from urban city edges to suburban areas.