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Condensation, Causes and Control

Technical Note

Condensation in buildings occurs when moist air contacts surfaces below the dew point temperature, leading to moisture accumulation that can cause serious damage including decay, mold growth, and structural deterioration. This publication provides comprehensive guidance on understanding, preventing, and controlling condensation in residential and light commercial construction.

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

The publication covers practical prevention methods such as reducing indoor moisture sources, installing proper vapor retarders, ensuring adequate ventilation, and incorporating continuous air barriers. The publication includes specific code requirements from the International Residential Code (IRC) and International Building Code (IBC), with detailed tables for vapor retarder classifications and minimum ventilation requirements.

Key sections include:

  • Condensation explained – fundamental principles of moisture and temperature

  • Condensation control – practical strategies for different building areas

  • Vapor retarder requirements – classification system and climate zone specifications

  • Ventilation requirements – minimum standards for attics and crawl spaces

  • Ventilation checklist – inspection guidelines and calculation examples

Published by APA — The Engineered Wood Association.

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