Unvented Roof Unvented Cathedral Ceiling Insulation

With an unvented cathedral ceiling it is critical to keep moist air and water vapor away from the roof sheathing where it can build up and lead to wood decay.

Unvented roof unvented cathedral ceiling insulation.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. The rigid foam will be fairly thick see sidebar how much insulation. Unvented attics and cathedral ceilings 2 air permeable insulation only irc r806 5 5 2 attic while the irc refers to this assembly as air permeable insulation only it also involves installation of rigid board insulation above the roof sheathing. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction.

Rigid foam above roof sheathing you can install all of the insulation above the roof sheathing but the foam has to be thick enough to meet minimum code requirements for ceiling r value. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Four options for building an unvented roof assembly option 1. It is also one of the most expensive and most building inspectors will not allow it to be left uncovered for fire code reasons.

Foil faced iso board can be cost effective insulation for finished attics and cathedral ceilings.