Investigation of Thermal Comfort and Energy Efficiency in Green-Roof Residential Buildings Under the Hot-Humid Climate of Benin City

Green roofing systems have attracted significant research interest as a passive thermal comfort and building energy performance strategy in tropical climates, yet empirically validated performance data in the specific hot-humid conditions of South South Nigeria remains scarce, limiting evidence-based advocacy for green roof adoption in the residential building sector. This study investigates the thermal comfort and energy performance implications of green roof retrofitting on a representative single-storey residential building under the hot-humid climate of Benin City, Edo State. A paired experimental design was employed, with side-by-side monitoring of an unmodified control building and an identical retrofitted test building at the same location over a 12-month period spanning dry and wet seasons. Internal and roof surface temperatures, relative humidity, and solar heat flux were continuously monitored at multiple points in both buildings using wireless sensor nodes logging at 15-minute intervals. Occupant thermal comfort was assessed periodically using structured questionnaires and ASHRAE 55 adaptive comfort model calculations. The green roof reduced the interior ceiling temperature by an average of 4.8 degrees Celsius during peak daytime hours and extended the daily cooling comfort window by 2.1 hours on average relative to the control. Energy simulation using EnergyPlus, calibrated against measured data, projected annual air conditioning energy savings of 31 percent in the green-roof building compared to the conventional baseline. Keywords: green roof, thermal comfort, energy efficiency, hot-humid climate, Benin City.