The unvented attic space is completely within the building thermal envelope.
Unvented finished attic 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.
Proper attic insulation is the best way to prevent heat loss in the winter and retain cool air in the summer.
This reduces latent air conditioning loads and provides further reductions in energy consumption.
Insulation approaches for unvented attics vary by climate.
If you don t want to use sips or nailbase there are four basic approaches.
It is a proven cost effective approach to creating a more energy efficient building particularly when the hvac system is located in the attic space.
When all of the insulation is tight to the roof deck the unvented enclosed rafter truss assembly or unvented attic is within the building envelope and the attic will be conditioned to have a similar temperature as the interior space.
Where the attic space is finished with drywall or other ceiling materials installed against the underside of the roof rafters while we prefer in floor insulation here we ll have to insulate the roof cavity between the rafters.
A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.
This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation.
Fibrous insulation fibrous insulation e g batt or blown in can be installed under the roof deck in the hot dry.
The advantages of unvented attic construction using spray foam insulation are numerous.
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.
Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.
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.
Four options for building an unvented roof assembly.
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.
Un vented hot roof designs indoors finished attic.
