Unvented Attic System

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.

Unvented attic system.

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. The energy savings touted by unvented attics can be as high as 20. In cold climates attic ventilation is a common method to remove humid air. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation.

An unvented attic system relies on an air seal and no vents to make the attic a conditioned space. Modifying the attic to create an indirectly conditioned attic space with icynene can significantly reduce energy consumption. 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.

Low slope and steep slope unvented roof systems i e. Building america research has demonstrated unvented conditioned attics can substantially improve energy performance while allowing home builders. 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.

Unvented conditioned attics the preference for a large segment of the u s. Housing industry has been to locate hvac systems in unconditioned attics but this is highly inefficient. 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.

Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs.