Unvented Roof Construction

Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs.

Unvented roof construction.

Control construction moisture content with tenting or temporary roofing when necessary. Unvented roofs have a number of advantages. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes.

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 assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. In pitched roof construction thermal insulation can be placed horizontally at ceiling level cold roof. Designers may view unvented attic i e.

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. Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. Ventilation becomes more difficult the more complicated a roof s construction is.

The optimum systems developed to date are dependent on the climate location. 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. An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. Designs and houses with unvented roof insulation systems have also been developed and constructed in cold and mixed climates.

Attic space enclosed rafter or joist space above normally occupied and conditioned interior space assemblies as an economical arrangement of roofing and insulation materials. Moisture content in roof structure must be less than 18 prior to covering. Un vented roofs operate on the principle that moisture entering the roof assembly can be controlled and that there is no need for venting to control moisture accumulation. However insulation placement in roof assemblies requires careful review to achieve acceptable hygrothermal performance levels and limit the potential for condensation within the system.