DAYLIGHTING OPTIMIZATION AND VISUAL COMFORT IN TROPICAL RETAIL ARCHITECTURE: SIMULATION-BASED EVALUATION OF A SHOPPING MALL IN KEFFI, NASARAWA STATE

Daylighting in large retail buildings is often treated as secondary, despite its impact on energy use and shopper experience. This study evaluates daylighting strategies in a prototype shopping mall in Keffi, Nasarawa State, focusing on visual comfort and balancing useful daylight with excessive solar exposure. Using a quantitative, simulation-based approach, the digital workflow integrated climate-based modeling, a Perez sky model, and a Radiance environment to evaluate a base case against three interventions: roof geometry adjustments, reflective interior finishes, and atrium openings. The base case performed poorly, recording 0% Spatial Daylight Autonomy (sDA) on both ground and first floors. Atrium openings achieved the most significant impact, elevating sDA to 100% on both levels. Roof geometry raised ground and first-floor sDA to 29% and 19%, while reflective finishes yielded 33% and 29%, respectively. However, increased daylight availability caused persistent glare and overexposure. Ground-floor Annual Sunlight Exposure (ASE) exceeded 70% across all scenarios, peaking in the atrium model at 81.387% on the ground floor and 75.912% on the first floor. Consequently, while atria are the most effective distribution strategy, they must be combined with roof geometry, reflective finishes, and targeted shading to provide a balanced framework for tropical Nigerian retail architecture