Unvented Attic System

In hot climates unvented attics are ideal where hvac equipment and ductwork are located in the attic.

Unvented attic system.

Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Modifying the attic to create an indirectly conditioned attic space with icynene can significantly reduce energy consumption. By using an air impermeable insulation like spray foam on the roof deck will stop any air movement.

The energy savings touted by unvented attics can be as high as 20. Openings between the attic and the outside are sealed and the underside of the roof is insulated. However unvented attics can reduce residential energy needs and are allowed by the code under certain conditions. 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. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. Unvented conditioned attics the preference for a large segment of the u s. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs.

The alternative is to have an unvented attic which means including the attic in the conditioned area of your home and keeping moisture out. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. Housing industry has been to locate hvac systems in unconditioned attics but this is highly inefficient. 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.

Building america research has demonstrated unvented conditioned attics can substantially improve energy performance while allowing home builders.