Unvented Attic Space

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

Unvented attic space.

No interior class i vapor retarders are installed on the ceiling side attic. Building america research has demonstrated unvented conditioned attics can substantially improve energy performance while allowing home builders to continue locating hvac systems in the attic space. The unvented attic space is completely contained within the building thermal envelope 2. In cold climates attic ventilation is a common method to remove humid air.

The unvented attic is indirectly conditioned space since heat and moisture transfer occurs through the top floor ceiling particularly if the ceiling is not airtight. Section 1203 3 says unvented attics where ceilings are applied directly to the underside of the roof framing members are permitted when all of the following conditions are met. The unvented attic space is completely within the building thermal envelope. There are typically no supply or return registers from the hvac system specifically located in an unvented attic space.

Air does not flow into the soffits and does not flow out of ridge or gable vents. Adding unvented attic insulation like spray foam seals the building envelope and stops airflow. This air seal will. However they require different approaches in different climate locations.

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. The energy savings touted by unvented attics can be as high as 20. No interior class i vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly or on the ceiling side of the unvented enclosed rafter assembly.

The entire attic becomes conditioned space eliminating drafts and temperature fluctuations. No interior vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly 2009 irc. Making the attic a conditioned space means the space will be the same temperature as the rest of your home. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings.

This system can help you avoid.