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

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.