Unvented Finished Attic Insulation

Proper attic insulation is the best way to prevent heat loss in the winter and retain cool air in the summer.

Unvented finished attic 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. This reduces latent air conditioning loads and provides further reductions in energy consumption. So it s time to pay close attention to what s happening up there. Fibrous insulation fibrous insulation e g batt or blown in can be installed under the roof deck in the hot dry.

The unvented attic space is completely within the building thermal envelope. If you don t want to use sips or nailbase there are four basic approaches. 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. The advantages of unvented attic construction using spray foam insulation are numerous.

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. 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. Un vented hot roof designs indoors finished attic. Insulation approaches for unvented attics vary by climate.

Four options for building an unvented roof assembly. 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. 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. The roof insulation and air barrier must follow the plane of roofing materials rather than diverge figure 2.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction. 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.