Abstract
Windows are critical components of residential façades, directly influencing daylight availability, natural ventilation, and indoor environmental comfort. In the hot-humid climate of Lagos, Nigeria, the increasing prevalence of inadequately proportioned window sizes in residential buildings has become a significant concern. This trend is largely driven by high urban density, security considerations, economic constraints, and weak regulatory enforcement. This study critically assesses the impact of undersized windows on thermal comfort, ventilation performance, daylight penetration, and overall urban livability in Lagos residential buildings with particular reference to Osapa London, Lekki. Drawing on field observations, empirical evidence, and comparative analyses of residential buildings with varying window-to-wall ratios (WWR), the research evaluates how reduced window dimensions affect indoor thermal conditions, airflow effectiveness, and daylight adequacy, as well as occupants' reliance on artificial lighting and mechanical cooling systems. Findings indicate that inadequately proportioned windows significantly restrict passive environmental performance, resulting in increased energy consumption, occupant discomfort, and diminished quality of life. The study further examines how window size distribution interacts with building orientation and surrounding urban form to influence environmental outcomes. Based on the findings, strategies are proposed to optimise window sizing in ways that balance façade design constraints with indoor environmental performance. The research ultimately establishes window size as a critical determinant of comfort, energy efficiency, and sustainable urban livability in Lagos residential developments.