Ventilation Effectiveness: Overview of Terminology and Analysis of Influencing Parameters

Ventilation effectiveness evaluates the performance of ventilation systems by assessing air exchange and contaminant removal. Optimising ventilation effectiveness in mechanical ventilation systems reduces the required supply airflow rate while maintaining adequate indoor air quality. This review clarifies inconsistent definitions of ventilation effectiveness in standards and literature and provides a comprehensive overview of terms, definitions, and relevant parameters. The review also analyses the influence of variable and building-fixed parameters on ventilation effectiveness using data from selected studies. Contaminant position and supply/exhaust position had the greatest impact on ventilation effectiveness, with maximum absolute changes of 2.1 and 0.94, respectively. Variable parameters, such as air change rate and temperature difference, showed moderate mean absolute changes of 0.28 and 0.15 but significant maximum deviations of 0.85 and 0.4. Building-fixed parameters, including room size and aspect ratio, showed the least influence, with mean absolute changes below 0.1. These results highlight the importance of parameter interactions, such as short-circuit flows caused by higher air velocities. In EN 16798-1:2022, design values for required airflow are based on a ventilation effectiveness of 1. However, the analysis shows large variations around this value, indicating potential deficits in air quality and opportunities for energy savings. This review highlights the need for holistic system design and consideration of parameter interactions to optimise energy efficiency and air quality.