Unvented Attic System

Modifying the attic to create an indirectly conditioned attic space with icynene can significantly reduce energy consumption.

Unvented attic system.

The energy savings touted by unvented attics can be as high as 20. In hot climates unvented attics are ideal where hvac equipment and ductwork are located in the attic. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. 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.

However unvented attics can reduce residential energy needs and are allowed by the code under certain conditions. The alternative is to have an unvented attic which means including the attic in the conditioned area of your home and keeping moisture out. By using an air impermeable insulation like spray foam on the roof deck will stop any air movement. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings.

However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. Low slope and steep slope unvented roof systems i e. In cold climates attic ventilation is a common method to remove humid air. Unvented conditioned attics the preference for a large segment of the u s.

An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Openings between the attic and the outside are sealed and the underside of the roof is insulated. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. Unvented attic assemblies code notes 2009 irc 2012 irc adequate attic ventilation is a long standing requirement in building codes for moisture control.

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.