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Water Vapor Permeance of Wood Structural Panels and Wood Wall Construction

Technical Note

Moisture control is critical for preventing damage in wood-framed structures. While water leaks are the primary concern, water vapor movement through wall assemblies can also lead to condensation and moisture accumulation if not properly managed. This technical note addresses the water vapor permeance characteristics of wood structural panels and provides essential guidance on vapor retarder placement and wall system design to minimize moisture-related problems in buildings.

This publication is designed for: architects, engineers, designers, builders

The document explains water vapor permeance testing methods, classifications of vapor retarders per building codes, and presents research data comparing the permeance of various building materials.

Key sections include:

  • Moisture movement and water vapor permeance

  • Basic vapor management design considerations

  • Plywood and OSB as smart vapor retarders

  • Design considerations for durable wall assemblies

Published by APA — The Engineered Wood Association.

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