Vapor Retarders: Reducing Moisture Risk in Frame Walls (TechNote)

This TechNote provides an overview of building code requirements and design considerations for vapor retarders. The focus is on climate-specific recommendations for selecting interior vapor retarder products for frame walls.

Vapor retarder is a material or product that controls the migration of moisture due to vapor diffusion.

TechNotes: Best Practices for Home Builders
In recent years, building codes for energy efficiency and related standards have been amended to require greater amounts of insulation in exterior wall and roof assemblies, including continuous insulation on exterior walls, higher levels of building air tightness, and mechanical ventilation.
NAHB’s Construction Technology Research Subcommittee worked with Home Innovation Research Lab to develop these TechNotes to help builders navigate these new code requirements and implement best practices to avoid building performance issues related to interior humidity levels, condensation in wall and roof assemblies, and interior air quality.