Why is mechanical ventilation necessary as buildings become more air-tight?

Mechanical ventilation is necessary as buildings become more air-tight primarily because it ensures adequate airflow and provides a fresh air supply. As modern construction practices focus on creating energy-efficient, tightly sealed buildings, the natural infiltration of outdoor air is significantly reduced. This reduction can lead to a buildup of indoor air pollutants, increased humidity, and insufficient oxygen levels.

In such airtight environments, relying solely on natural ventilation is often insufficient to maintain healthy indoor air quality. Mechanical ventilation systems actively supply fresh air from outside and promote proper circulation within the space, helping to dilute and exhaust indoor contaminants. This is crucial for health and comfort, as it helps prevent the accumulation of pollutants such as volatile organic compounds, carbon dioxide, and excess humidity. Thus, mechanical ventilation plays a vital role in maintaining a healthy indoor environment in increasingly sealed buildings.