Unvented Roof Construction

Inclined along the line of rafters warm roof or positioned within the roof structure to form an insulated void room in roof which can result in warm and cold roof areas.

Unvented roof construction.

Ventilation becomes more difficult the more complicated a roof s construction is. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. Designers may view unvented attic i e. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.

Moisture content in roof structure must be less than 18 prior to covering. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. Unvented roofs have a number of advantages. In order for an un vented roof assembly to function properly the following conditions must be in place.

As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes. Designs and houses with unvented roof insulation systems have also been developed and constructed in cold and mixed climates. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.

Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. Control construction moisture content with tenting or temporary roofing when necessary. Attic space enclosed rafter or joist space above normally occupied and conditioned interior space assemblies as an economical arrangement of roofing and insulation materials. Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof.

An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. 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. Over the past five years several unvented roof insulation systems have been developed by the building science consortium for use primarily in hot dry and hot humid climate zones. In pitched roof construction thermal insulation can be placed horizontally at ceiling level cold roof.