Optimizing Horizontal Shading Devices for Daylight Performance and Energy Efficiency in Kathmandu's Office Buildings: A Multi-Objective Study Under Current and Future Climate Scenarios

This study optimizes horizontal shading devices for south-facing office façades in Kathmandu to balance daylight, energy, and visual comfort under current and future climates. From 210 simulations varying shading count, depth, and angle, pairwise dominance checking identified 33 mathematically Pareto-optimal configurations. However, mathematical optimality does not guarantee practical suitability. When constrained by minimum daylight requirements (sDA ≥ 50%), the viable design space collapses to 16 feasible configurations, of which only 3 achieve zero glare (ASE = 0). K-means clustering validated three design strategies: Energy-Efficient (n=11) with low EUI and zero glare but limited daylight; Balanced (n=14) with good daylight, low glare, and moderate EUI; and Daylight-Optimal (n=8) with high daylight but high EUI and glare. The recommended configuration (0.4 m depth, 0° angle, 6 louvers) achieves 51.2% sDA with zero glare and 21% energy savings. Under future scenarios (SSP2-4.5 and SSP5-8.5 to 2080), the energy advantage of optimized shading over unshaded alternatives nearly triples under worst-case warming, and the Pareto front shifts rightward while maintaining shape, which confirms that today's optimal designs remain optimal under any future pathway. These findings provide the first evidence-based, climate-resilient design guidelines for south-facing office façades in Kathmandu.