Unvented roof assemblies, such as conditioned attics and unvented cathedral ceilings, are becoming common in North American construction.  These assemblies are created by eliminating ventilation openings and moving the thermal, moisture and air control boundaries to the plane of the roof deck.  This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. Read more...

Roofs can be designed and constructed to be either vented or unvented in any hygrothermal zone. Air barrier systems are typically the most common approach, however, air pressure control approaches are becoming more common especially in cases involving remedial work on existing structures. Vapor diffusion should be considered as a secondary moisture transport mechanism when designing and building roofs. Specific vapor retarders are often unnecessary if appropriate air movement control is provided or if control of condensing surface temperatures is provided. Read more...