Simulation-Based Visual-Comfort and Energy-Optimised Lighting Design for Residential Buildings: A Comparative Study of Manual and DIALux-Based Approaches

This study presents a reproducible simulation-based framework for visual-comfort and energy-optimised lighting design in UK residential buildings using DIALux Evo. Circadian and biophilic principles inform the conceptual approach, specifically colour temperature selection aligned with occupant comfort - but the study measures only photopic illuminance (lux) and electrical energy consumption (kWh), explicitly excluding biological circadian metrics, dynamic controls, and daylight harvesting. A controlled comparative design evaluates twenty matched lighting scenes in one-bedroom flats, compliant with EN 12464‑1 and CIBSE LG9. The DIALux-optimised designs, incorporating LED luminaires in place of CFL luminaires used in existing manual designs, reduced mean energy consumption from 10.25 kWh to 8.68 kWh — a statistically significant reduction of 15.3% (t = 5.12, p = 1.2×10⁻⁵, d = 1.61) — while increasing mean illuminance from 165.86 lux to 205.14 lux (t = 3.084, p = 1.0×10⁻⁶, d = 0.81), improving CIBSE LG9 compliance across scenes. The framework offers a standards-aligned, reproducible methodology with direct relevance to UK Net Zero objectives, Part L compliance, and residential retrofit policy, providing actionable guidance for architects, engineers, and policymakers. It is acknowledged that the observed gains reflect the combined benefit of an integrated LED-plus-simulation workflow; the absence of a same-technology comparison condition is identified as the primary design limitation.