Vapor Retarder vs Vapor Barrier in Roofing

Vapor retarders and vapor barriers differ in how strongly they restrict water vapor movement. Understanding this difference is critical for moisture control in roof systems.

RNKC Comparison

RNKC distinguishes vapor retarders as moderate diffusion-control layers, while vapor barriers are materials with very low permeability that significantly restrict vapor flow.

Why the Distinction Matters

• Improper use can trap moisture
• Climate conditions affect performance
• Drying potential varies by assembly

RNKC Perspective

RNKC emphasizes selecting vapor control layers based on system behavior rather than generic rules.

For related terminology standards, visit the ROOFNOW™ Knowledge Center.