What are the three primary causes of air leakage in buildings?

The three primary causes of air leakage in buildings are indeed associated with stack effect, mechanical ventilation, and wind. The stack effect refers to the natural phenomenon where warm air rises and creates pressure differences within a building, leading to air movement in and out, especially in tall structures. This movement can be significant and is influenced by temperature variations between the inside and outside of the building.

Mechanical ventilation systems can introduce air exchange as well. These systems are designed to manage indoor air quality by providing controlled air movement, but they can also be a source of unintentional air leakage if not properly sealed or maintained. This mechanical airflow can contribute to changes in pressure that impact how air leaks from and into the building.

Wind plays a crucial role as well, as it creates pressure differences on the building envelope. When wind hits the building’s exterior, it can force air into cracks and openings, or pull air out, depending on the direction of the wind. This dynamic is particularly noticeable in areas with significant exposure to wind.

By understanding these factors—stack effect, mechanical ventilation, and wind—professionals can better target air leakage testing and remediation strategies to improve building performance and comfort.