Unvented Attic Batt Insulation

To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents soffits etc which make it difficult to achieve an airtight ceiling plane.

Unvented attic batt insulation. However unvented attics can reduce residential energy needs and are allowed by the code under certain conditions. Although taped rigid foam under the rafters would improve the situation by reducing the chance that warm humid air would migrate through the batts and contact the cold roof sheathing the detail is still risky especially if there are any wiring penetrations. 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 assemblies code notes 2009 irc 2012 irc adequate attic ventilation is a long standing requirement in building codes for moisture control.

You should never use fiberglass batts to insulate an unvented sloped ceiling. 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. If you don t want to use sips or nailbase there are four basic approaches. Martin s post focuses on the marketing of owens corning s propink unvented attic insulation system.

Owens corning calls this proprietary insulation method the propink high performance conditioned attic system. 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. The owens corning system is only allowed by code in zones 2b 3b with tile roofs. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation.

Four options for building an unvented roof assembly. Owens corning a leading manufacturer of fiberglass insulation is now promoting a package of products basically blown in fiberglass insulation and a new type of insulation netting to create unvented conditioned attics. An alternate to spray foam insulation in an unvented attic is plenum trusses which allow you create a reverse bulkhead above the ceiling plane that is insulated. An unvented attic air sealed with spray foam insulation limits outdoor air entry and as a result indoor combustion air should not be considered available for fuel fired combustion appliances located within the attic space.