Finishing An Unvented Attic

Residential unvented attics.

Finishing an unvented attic. For unvented attics having the spray foam layer applied continuously from the roof wall intersection to the roof peak at the specified thickness encapsulating the entire interior surface area of the attic will hinder airborne moisture entry while providing an energy efficient environment. But according to energy star the average home loses about 20 percent of the air that moves through the hvac system due to. Code requirements vary across the country. The same conditions apply for moisture.

By moving the vapor control layer to the roof deck it prevents moisture related problems. Traditionally we place hvac and ductwork and often storage up there and insulate the floor of the attic. The entire attic becomes conditioned space eliminating drafts and temperature fluctuations. 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.

An attic is simply the space between a pitched roof deck and the rest of the house. The roof deck in an unvented attic must be exceptionally airtight. The irc has permitted unvented conditioned attics since 2006 with certain requirements. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation.

Converting your attic into usable finished space can increase the value of your home by maximizing the available square footage. Coverage gaps could lead to moist outdoor air entry. 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. The acceptance of unvented conditioned attics continues to grow among builders and building officials.