Designing Intensive Care Unit Windows in a Mediterranean Climate: Efficiency, Daylighting, and Circadian Response

Hospital intensive care units (ICUs) frequently experience inadequate lighting conditions, with low daytime and excessive nighttime illuminance, which can negatively affect patient recovery and the work performance of health personnel. This study examines the impact of window design parameters—specifically, window-to-wall ratio (WWR) and window position—and interior surface reflectance on visual comfort, lighting performance, energy consumption, and human well-being in intensive care units (ICUs) in Mediterranean climates, according to orientation. Using dynamic lighting metrics, such as daylight autonomy (DA) and circadian stimulus autonomy (CSA), this research quantifies the influence of these design factors. The results suggest that a WWR of 25% is optimal for achieving sufficient DA and CSA values, with centered window configurations preferred for uniform daylight distribution and circadian stimulus. This study further emphasizes the significance of interior reflectance, recommending bright coatings to maximize outcomes, while advising against dark finishes, particularly in north-facing rooms or with smaller WWRs. Although Seville shows slightly better performance than Barcelona, the proposed configurations are effective across both locations, highlighting the prioritization of window sizing, positioning, and reflectance over Mediterranean geographical differences. These findings offer practical guidance for ICU design to enhance natural lighting, supporting patient recovery and overall well-being through improved circadian alignment.