Unvented Attic System

Unvented conditioned attics the preference for a large segment of the u s.

Unvented attic system.

By using an air impermeable insulation like spray foam on the roof deck will stop any air movement. Openings between the attic and the outside are sealed and the underside of the roof is insulated. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. They are designed without ventilation openings and the attic is conditioned like the rest of the living space.

Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. Housing industry has been to locate hvac systems in unconditioned attics but this is highly inefficient. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. The alternative is to have an unvented attic which means including the attic in the conditioned area of your home and keeping moisture out.

The energy savings touted by unvented attics can be as high as 20. An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Low slope and steep slope unvented roof systems i e. Unvented attic assemblies code notes 2009 irc 2012 irc adequate attic ventilation is a long standing requirement in building codes for moisture control.

In cold climates attic ventilation is a common method to remove humid air. Modifying the attic to create an indirectly conditioned attic space with icynene can significantly reduce energy consumption. 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 hot climates unvented attics are ideal where hvac equipment and ductwork are located in the attic.

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.