Study of Thermal Performance of Corrugated Iron Sheet Roofing in Residential Buildings in Lokoja, Kogi State

Corrugated iron sheet roofing dominates Nigerian residential construction yet its thermal performance is notoriously poor, generating extreme heat gain in occupied spaces that adversely affects inhabitant comfort and health, particularly in hot climates such as that of Lokoja. This study investigates the thermal performance of corrugated iron sheet roofing in low and medium-income residential buildings in Lokoja, Kogi State, where the confluence of tropical humidity and dry season heat creates demanding climatic conditions. Field measurements were conducted in thirty residences across Ganaja, Felele, and Zango Daji neighbourhoods, recording under-roof air temperatures, indoor operative temperatures, roof surface temperatures, and outdoor reference conditions at hourly intervals over three weeks. Building configurations were documented including ceiling provision, roof space height, roof colour, and insulation status. Comparative analysis was conducted between roofed buildings with and without ceiling boards. Results show that average mid-afternoon indoor operative temperatures in unceilinged buildings exceeded outdoor air temperature by up to 6.4 degrees Celsius. Ceiling provision reduced indoor temperature by an average of 3.8 degrees Celsius relative to unceilinged equivalents. Dark-coloured iron sheets produced surface temperatures exceeding 75 degrees Celsius under direct solar radiation. White-painted iron sheet roofs reduced surface temperatures by an average of eighteen degrees Celsius compared to unpainted surfaces. The study recommends the adoption of reflective cool-roof coatings and mandated ceiling provision in new construction through the Kogi State building code, identifying these as low-cost, high-impact thermal comfort interventions. Keywords: corrugated iron roof, thermal performance, residential buildings, Lokoja, thermal comfort.