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.