What major factor contributes to many vapor-related moisture problems?

Air leakage plays a significant role in vapor-related moisture problems because it allows humid air from outside to enter the building, or vice versa. When warm, moist air comes into contact with cooler surfaces, such as walls or windows, condensation can occur. This condensation creates an environment that promotes mold growth and may lead to structural damage over time.

Air leakage also hinders the performance of vapor barriers and insulation, as it can carry moisture-laden air into spaces where it's not needed. Proper sealing of a building's envelope is crucial in controlling moisture levels and maintaining indoor air quality, while limiting the potential for water damage and promoting overall energy efficiency.

In contrast, while water leakage can contribute to moisture problems, air leakage typically exacerbates the issue because it continually introduces moisture into areas that may not be adequately protected, thus compounding the risks associated with vapor-related issues.