Unvented Roof In Arid Climate

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Unvented roof in arid climate. The building science corporation team tested implementation of an unvented tile roof assembly in a hot humid climate insulated with air permeable insulation netted and blown fiberglass. An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. In this case you can learn a lot from foam tech s article vented vs. Unvented attic assemblies code notes 2009 irc 2012 irc.

Unvented roofs which provides a detailed explanation of each. When constructing unvented roofs with asphalt shingles in hot humid climates a vapor barrier must be installed between the asphalt shingles and the roof deck. Of unvented roofs by more than 50 percent and allow the use of dense pack cellulose in retrofit applications without risk. Unvented roof assemblies with ccspf work well in all climate zones and serve several important functions.

Near term the moisture content of the roof sheathing b. If air permeable insulation is proposed to be placed under the roof sheathing. In climate zones 5 through 8 where air permeable insulation is proposed verify that a vapor retarder is called out immediately below the insulation. Asphalt shingles store water from dew condensation due to night sky cooling and rain.

Code change allowing use of air permeable insulation in the construction of unvented conditioned attics. Field testing an unvented roof with fibrous insulation and tiles builder. Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof. Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation.

Controls airflow ccspf is air impermeable adheres well to almost all construction surfaces and expands to fill voids creating an air seal and eliminating air leakage. When ductwork and mechanical systems are located in the roof an unvented roof is generally preferred. An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot.