In a 100 square ft wall, how much water can diffuse through drywall without a vapor diffusion retarder in a year?

The correct answer is based on the understanding of how drywall interacts with moisture in the environment. In general, without a vapor diffusion retarder, drywall allows moisture to diffuse through it over time.

Research indicates that, on average, about 1 cup of water can diffuse through a 100 square foot wall of standard drywall within a year. This value stems from studies on permeability rates of building materials, which take into account various environmental conditions, such as humidity and temperature, affecting moisture migration.

This highlights the importance of moisture management in wall assemblies, particularly in areas with high humidity levels or significant temperature fluctuations. If a vapor diffusion retarder is not used, the potential for moisture accumulation and related issues, such as mold and structural damage, increases over time.

Understanding this diffusion process is crucial for building inspections and home performance assessments, as it informs decisions about insulation, air sealing, and moisture control strategies within structures.