Unventilated Roof Construction

The ever increasing levels of thermal insulation required by thermal regulations can result in a higher risk of condensation forming on those elements not enclosed by this insulation e g.

Unventilated roof construction.

Because the drying capacity of unvented roof assemblies is inherently lower than vented ones it is especially critical to control built in moisture during 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. Breather membrane in colours. Control construction moisture content with tenting or temporary roofing when necessary.

Moisture content in roof structure must be less than 18 prior to covering. Eliminating traditional ventilation and the potential condensation risk associated with large voids of cool air make this the optimum pitched roof solution. For designers the advantage of using unventilated construction comes from removing the necessity to provide a ventilated cavity below the sarking. Poorly insulated ducting can cause heat loss in colder months and the loss of conditioned air in the summer in vented attics.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. Together with not having to provide a ventilation pathway the technique permits insulation to be installed within the full depth of the rafter.