In hot, humid regions like Nigeria, sustainable alternatives to energy-intensive air conditioning are crucial for achieving indoor thermal comfort. This research investigates the impact of external planter placement and Leaf Area Index (LAI) on enhancing comfort within a lecture room through simulation. The researchers employed a quantitative methodology using EnergyPlus in DesignBuilder to compare a base case without plants against four experimental cases, where planters were placed at varying distances of 300 mm to 1200 mm from the building's exterior wall. The researchers simulated each case across three LAI values (3, 4, and 5) and conducted a comparative analysis of thermal comfort metrics — operative temperature, Predicted Mean Vote (PMV), and Predicted Percentage Dissatisfied (PPD). The findings indicate that incorporating external planters consistently improved indoor thermal comfort relative to the base model. Planters situated closest to the exterior wall (300mm) yielded the most significant reduction in operative temperature and the lowest PMV and PPD values. While increasing LAI generally resulted in minor improvements, the distance of the planters exhibited a more pronounced influence on thermal performance. This study highlights the efficacy of strategically positioning external vegetation to enhance indoor thermal comfort in hot-humid climates. Simulation-based optimisation provides valuable insights for architects and urban planners in designing effective passive cooling strategies, considering both plant distance and plant density, thereby promoting sustainable building design and energy conservation
