This report provides:

• The background to a comprehensive R and D project to study the potential benefits of providing ventilation in above-grade wall systems, especially those used in residential construction in North America.
• A synthesis of the work done and the associated 13 reports which were delivered to the main sponsor of the project, ASHRAE.
• Guidelines for the implementation and use of ventilation in above-grade enclosure wall systems. The main conclusion is that ventilation does contribute to the control of moisture in wall systems and that, where feasible and needed, ventilation should be provided.