Unvented Attic System

Unvented attic assemblies code notes 2009 irc 2012 irc adequate attic ventilation is a long standing requirement in building codes for moisture control.

Unvented attic system.

Unvented conditioned attics the preference for a large segment of the u s. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. Building america research has demonstrated unvented conditioned attics can substantially improve energy performance while allowing home builders. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs.

However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. Openings between the attic and the outside are sealed and the underside of the roof is insulated. In hot climates unvented attics are ideal where hvac equipment and ductwork are located in the attic. By using an air impermeable insulation like spray foam on the roof deck will stop any air movement.

Modifying the attic to create an indirectly conditioned attic space with icynene can significantly reduce energy consumption. However architects of these compact roof assemblies must consider vapor permeance and arrangement of the materials to produce acceptable hygrothermal performance and low risk of condensation in the resulting conditioned attic space. The energy savings touted by unvented attics can be as high as 20. The alternative is to have an unvented attic which means including the attic in the conditioned area of your home and keeping moisture out.

An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. Insulation and air barrier are applied directly to the underside of the roof deck are common in applications where designers are seeking cost effective and energy efficient roof assemblies.

In cold climates attic ventilation is a common method to remove humid air.