Assessment of ventilation system efficiency in terms of energy performance is crucial for their optimal design and operation. Current energy performance metrics lack consideration for the cooling effect of air movement, a key aspect encouraged by regulations to enhance energy-efficient thermal comfort. To address this gap, a novel index named Equivalent Thermal Utilization Effectiveness (ETUE) is proposed by this chapter. ETUE incorporates the cooling effect of air movement by quantifying it through the standard effective temperature, leading to a corresponding reduction in the occupied zone’s air temperature. By integrating this equivalent reduction in air temperature into the existing Thermal Utilization Effectiveness (TUE) index, ETUE provides a more comprehensive assessment of ventilation system performance. Experiments focusing on stratum ventilation, a system known for leveraging air movement for cooling, have demonstrated the necessity of replacing TUE with ETUE. Failure to do so could lead to a significant decline in accuracy rates in energy performance evaluations (0–38.5%). The cooling effect of air movement contributes substantially (up to 86.8%) to the overall energy performance of ventilation systems. The proposed ETUE index represents a significant step forward in promoting the adoption of ventilation systems that harness air movement to enhance energy efficiency and thermal comfort in building environments.