Impact of climate change on sky conditions over nearly three decades in a tropical urban environment: A simulation analysis for daylight performance in Makassar City

This study evaluates climate change impacts on daylight availability in Makassar, Indonesia, through integrated analysis of meteorological data (1995–2023) and daylight performance simulations across multiple building configurations. Sunshine duration data demonstrated an exceptional correlation with solar radiation measurements (R² = 0.988), validating its use as a reliable proxy in data-limited regions. Statistical analysis revealed remarkable temporal stability, with a mean sunshine duration of 2847 ± 156 h, showing no significant trends (p = 0.68). The sky condition distributions remained consistent between the following periods: clear-sky (12.3 % vs. 12.4 %), intermediate (73.0 % vs. 72.6 %), and overcast (14.7 % vs. 14.9 %) conditions, with paired t-tests confirming no statistically significant changes (p > 0.05). However, small seasonal changes may show possible changes in the monsoon timing. A daylight performance analysis across window-to-wall ratios (WWR 20 %, 30 %, and 40 %) revealed the critical design thresholds for tropical office buildings. The south orientation demonstrated optimal Annual Sunlight Exposure (ASE) performance (0 % with shading), while the west orientation showed extreme values reaching 50–53 % without shading at WWR 40 %. Shading systems proved essential, reducing ASE from 21.15 % to 14.42 % in the west orientation. The East and West orientations achieved 100 % Spatial Daylight Autonomy (sDA) regardless of configuration, while the North and South orientations showed declining sDA values between study periods, suggesting differential climate impacts. A WWR of 30 % emerged as optimal, achieving universal 100 % sDA while maintaining manageable solar exposure. The findings guide climate-responsive tropical design, highlighting daylight optimization and solar control interplay, with shading transforming from optional to mandatory.