Unvented Attic Ceiling Assembly

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.

Unvented attic ceiling assembly. Attic space enclosed rafter or joist space above normally occupied and conditioned interior space assemblies as an economical arrangement of roofing and insulation materials. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Sign up log in. Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons.

In an unvented attic assembly air impermeable insulation is applied directly to the underside of the structural roof deck and is tied into the insulation located in the walls so that the roof system becomes part of the insulated building enclosure. Poorly insulated ducting can cause heat loss in colder months and the loss of conditioned air in the summer in vented attics. However unvented attics can reduce residential energy needs and are allowed by the code under certain conditions. The least tolerant roof assemblies in either climate are the unvented closed cell polyurethane roof assembly due to trapped moisture and slow drying of the roof sheathing up to 12 months in miami fl and 27 months in boston ma.

No interior class i vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly. Log in or create an account to post an answer. Unventilated attics are common where roof assemblies are complex and it s difficult to create a sealed ceiling plane. Unvented attic assemblies code notes 2009 irc 2012 irc adequate attic ventilation is a long standing requirement in building codes for moisture control.

If you don t want to use sips or nailbase there are four basic approaches. The unvented attic space is completely within the building thermal envelope. Designers may view unvented attic i e. Four options for building an unvented roof assembly.