What type of movement accounts for the majority of water vapor movement in building cavities?

Air movement accounts for the majority of water vapor movement in building cavities due to the principles of airflow and pressure differences within the structure. When air circulates through building envelopes, it carries water vapor along with it. This movement can occur through various pathways, including leaks, gaps, or mechanical ventilation systems.

Air movement is influenced by temperature changes, humidity levels, and wind pressure, which all contribute to the migration of moisture-laden air. As the air moves, it can transport significant amounts of water vapor from one area to another, such as from wet to drier areas, which is crucial in understanding moisture management within a building. This dynamic is essential for preventing issues like mold growth and material degradation caused by excess moisture trapped in cavities.

The other options represent concepts that contribute less to the overall movement of water vapor. Liquid movement pertains to the movement of liquid water, which plays a different role in moisture control, while solid movement doesn't apply because solids do not transport water vapor. Vapor movement alone, while relevant, lacks the broader context of how moving air facilitates the transport of water vapor more effectively in building environments.