Analysis of thermal comfort and indoor air quality in a mechanically ventilated basement bank vault

¹ Department of Mechanical Engineering, School of Science and Technology, Pan Atlantic University, Lagos, Nigeria
² Department of Aeronautics and Astronautics, Faculty of Engineering and Technology, Kwara State University, Malete, Kwara State, Nigeria.
³ Department of Civil Engineering & Environmental Engineering, University of Lagos, Lagos, Nigeria.
⁴ Department of Mechanical Engineering, Faculty of Engineering and Technology of Environmental, University of Ilorin, Ilorin, Nigeria.
⁵ Department of Building Technology, College of Environmental, Bells University of Technology, Ota, Nigeria.

^* Corresponding author: banyaegbuna@pau.edu.ng

Abstract

Indoor air quality (IAQ) and thermal comfort are critical for health and productivity in enclosed basements. This study investigates a mechanically ventilated bank vault, comparing the performance of mixing ventilation (MV) and displacement ventilation (DV). An occupant survey captured environmental complaints, while field measurements recorded carbon dioxide (CO₂), radon, fine particulates (PM2.5), and thermal parameters. Computational Fluid Dynamics (CFD) and analytical models were used to determine Air Change Efficiency (ACE), Contaminant Removal Effectiveness (CRE), Predicted Mean Vote (PMV), and Predicted Percentage Dissatisfied (PPD). The DV system, supplied at low-level inlets with ceiling exhaust, significantly improved air distribution and pollutant removal. Results showed ACE increased from 0.41 (MV) to 0.68 (DV). CRE values for CO₂, radon, and PM2.5 were 1.52, 0.79, and 1.12, respectively, outperforming MV. Comfort also improved, with DV achieving a near-neutral PMV (-0.03) and 5% dissatisfaction, compared to a slightly warm PMV (0.29) and 6.7% dissatisfaction under MV. Additionally, an air curtain at entrances helped reduce particulate ingress. Overall, DV demonstrated superior IAQ and comfort, offering practical guidance for retrofitting HVAC systems in basements and other confined urban workplaces.