Window Typologies as Determinants of Indoor Air Quality in Tropical African Buildings: A Multi-Variable Assessment of Office Spaces

Indoor air quality (IAQ) is a key determinant of health and productivity, particularly in office environments in tropical Africa where natural ventilation predominates and window typology is a critical but understudied factor influencing it. This study examined the impact of window typologies and associated architectural features on IAQ parameters in government office buildings in Enugu, Nigeria. A cross-sectional observational/experimental design was used in 54 naturally ventilated offices drawn from three government secretariat complexes. Offices were classified by window type (casement, projecting, or louvered + projecting) and architectural features. IAQ parameters measured included carbon monoxide (CO), carbon dioxide (CO₂), formaldehyde (HCHO), total volatile organic compounds (TVOCs), particulate matter (PM₂.₅), temperature, and relative humidity (RH). Data were analyzed using ANOVA and multivariate regression, controlling for other architectural features. Significant differences in IAQ were observed across window typologies. Offices with projecting windows recorded the highest mean concentrations of CO₂ (429 ppm), HCHO (0.028 mg/m³), TVOCs (0.082 mg/m³), RH (70.2%), and PM₂.₅ (7.0 µg/m³). By contrast, casement windows provided the lowest pollutant loads, including PM₂.₅ (4.1 µg/m³), HCHO (0.021 mg/m³), and TVOCs (0.018 mg/m³). Regression models confirmed that projecting and louvered + projecting windows were significantly associated with higher levels of HCHO, RH, and PM₂.₅ compared to casement windows. These findings demonstrate that window typology is a decisive determinant of IAQ in tropical African office buildings. Casement windows consistently provided better IAQ relative to projecting and louvered systems. The results emphasize the need to integrate IAQ considerations into early stages of architectural design, particularly in naturally ventilated settings where mechanical systems are scarce.