Finishing An Unvented Attic

The acceptance of unvented conditioned attics continues to grow among builders and building officials.

Finishing an unvented attic. Residential unvented attics. By moving the vapor control layer to the roof deck it prevents moisture related problems. An attic is simply the space between a pitched roof deck and the rest of the house. Code requirements vary across the country.

This reduces latent air conditioning loads and provides further reductions in energy consumption. With unvented attics the air barrier vapor and thermal controls are installed at the roof deck. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation. 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.

If your home is smaller than other homes in your area or simply lacks the necessary amount of storage or living space for your family finishing your attic is a relatively inexpensive way to increase your usable space. 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.

Converting your attic into usable finished space can increase the value of your home by maximizing the available square footage. The irc has permitted unvented conditioned attics since 2006 with certain requirements. 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. Coverage gaps could lead to moist outdoor air entry.