Unvented Roof Assembly

Un ven ted roof ˌənˈven t əd ro of an unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation.

Unvented roof assembly.

Read all of r806 5 carefully. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. 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 should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation.

Two potential unvented roof assemblies. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. If you don t want to use sips or nailbase there are four basic approaches. Four options for building an unvented roof assembly.

It s not and so code doesn t require r value ratios. In some climates it requires a vapor barrier. This is a mis interpretation of the code. They are designed without ventilation openings and the attic is conditioned like the rest of the living space.

Monolithic continuous exterior insulation ci above structural sheathing. Figure 6 describes open cell spray foam as air permeable. Recent building codes only allow unvented roof assemblies for pitches 3 12 and greater irc 2015 section r806 5 2 7. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof 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.