Vented And Unvented Roof Assembly

Moisture content in roof structure must be less than 18 prior to covering.

Vented and unvented roof assembly.

Control construction moisture content with tenting or temporary roofing when necessary. 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. They are designed without ventilation openings and the attic is conditioned like the rest of the living space.

In other words vented roofs may well be the best design for one home while an unvented roof will be a better solution for another home. An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot. Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs.

These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.