Unvented Roof Assembly

This is a mis interpretation of the code.

Unvented roof assembly.

If you don t want to use sips or nailbase there are four basic approaches. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Read all of r806 5 carefully. 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.

Recent building codes only allow unvented roof assemblies for pitches 3 12 and greater irc 2015 section r806 5 2 7. Four options for building an unvented roof assembly. Two potential unvented roof assemblies. In some climates it requires a vapor barrier.

This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. If air gaps are present between insulation layers convection currents can significantly reduce the performance of the assembly and compromise durability. 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. Monolithic continuous exterior insulation ci above structural sheathing.

Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof. Insufficient fill below the impermeable insulation layer. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.

It s not and so code doesn t require r value ratios.