This paper focuses on the mathematical simulation modeling of air exchange rates in buildings, employing a methodology that integrates pressure differences, stack effect, wind pressure, and forced ventilation. It includes a detailed relationship between CO2 concentration dynamics and air exchange, presenting equations and calculations for varying CO2 levels over time. Using IWEC data, the study delivers an hourly calculation of natural air exchange, considering both internal and external factors that influence air flow. The research zeroes in on the energy performance of multi-story buildings in relation to window air permeability, using a dynamic grid model compliant with EN standards. By examining rooms with different orientations under Kyiv's climate data, it identifies variations in air exchange rates due to building height, wind dynamics, and ventilation influences, along with effects on heat loss and energy demands. The findings reveal that natural air exchange rates often fall below standard values, impacting the building’s energy demand and potentially leading to heating system shutdowns during transitional seasons. Conclusively, the study offers strategies for optimizing energy consumption, contributing to the understanding and enhancement of energy-efficient building design and management. The research’s references span across building information modeling, energy analysis tools, sustainable certifications, and thermal performance assessments, encompassing a broad spectrum of building energy systems and modeling studies.