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 2,847 ± 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.