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. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. In some climates it requires a vapor barrier. Two potential unvented roof assemblies. 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 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. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. If air gaps are present between insulation layers convection currents can significantly reduce the performance of the assembly and compromise durability. Figure 6 describes open cell spray foam as air permeable.

Monolithic continuous exterior insulation ci above structural sheathing. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. If you don t want to use sips or nailbase there are four basic approaches. Read all of r806 5 carefully.

It s not and so code doesn t require r value ratios. Insufficient fill below the impermeable insulation layer. This is a mis interpretation of the code. Four options for building an unvented roof assembly.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.