This paper examines the effectiveness of two different window opening configurations for single-sided ventilation. The study’s results were obtained through monitoring in a test building located in Lower Austria. Initial findings from the summer and winter testing periods in 2024 are presented and used to evaluate various models employed in simulation tools to estimate air change rates in single-sided window ventilation. These models are commonly used in simulations that assess indoor thermal comfort, air quality, and overall building performance. While ventilation plays a critical role in these simulations, few studies have focused on rigorous validating of such ventilation models. Ventilation issues are often suspected to contribute to the performance gap between simulated results and observed building performance outcomes. A range of standards and recent scientific research suggest different models for estimating air change rates. Such models typically require various input parameters related to room and outdoor conditions. This contribution assesses the reliability of air change rates derived from such common estimation methods by utilising data of two test room in the case study building. Tracer gas measurements were conducted across multiple window opening configurations, and air change rates were calculated based on the concentration decay of the tracer gas. The findings provide validation and verification of simulation results, offering recommendations for selecting the most accurate models based on the study’s experiments.