Which type of movement accounts for more than 98% of all water vapor movement in building cavities?

Air movement accounts for more than 98% of all water vapor movement in building cavities because it involves the transport of moisture within the air that circulates through these spaces. This movement can be driven by various factors such as wind pressure, stack effect, and mechanical ventilation systems, all of which facilitate the transfer of air—and consequently water vapor—through building assemblies.

In the context of building science, understanding the significance of air movement is crucial for managing humidity levels and preventing moisture issues like mold growth or deterioration of materials. While diffusion and convection also play roles in moisture transfer, they contribute much less significantly compared to the predominant influence of air movement in typical building conditions. Evaporation is a critical process in generating water vapor, but it does not account for the transport of that vapor through building cavities once it is present. Thus, recognizing air movement as the primary mechanism reinforces the importance of controlling air leaks and ventilation strategies in maintaining a healthy indoor environment.