Unvented Roof Construction

They are designed without ventilation openings and the attic is conditioned like the rest of the living space.

Unvented roof construction.

Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. 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. Designs and houses with unvented roof insulation systems have also been developed and constructed in cold and mixed climates. 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. Unvented roofs have a number of advantages. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof 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.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. However insulation placement in roof assemblies requires careful review to achieve acceptable hygrothermal performance levels and limit the potential for condensation within the system. 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. As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes.

Ventilation becomes more difficult the more complicated a roof s construction is. 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. In order for an un vented roof assembly to function properly the following conditions must be in place. The optimum systems developed to date are dependent on the climate location.

Designers may view unvented attic i e. Moisture content in roof structure must be less than 18 prior to covering. An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof.