Unvented Conditioned Attic

This sheathing is less than a year old.

Unvented conditioned attic.

Adding unvented attic insulation like spray foam seals the building envelope and stops airflow. Unventilated attics are common where roof assemblies are complex and it s difficult to create a sealed ceiling plane. Among the early promoters of conditioned attics was joe lstiburek a principal of the building science corporation. Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons.

The intended purpose was to allow warm air and moisture to escape. Traditionally building codes have required attic ventilation. Energy conservation moisture management. This system can help you avoid.

Poorly insulated ducting can cause heat loss in colder months and the loss of conditioned air in the summer in vented attics. The builder or homebuyer if the buyer has purchased prior to construction may want the attic space to be conditioned for additional living or storage space. Making the attic a conditioned space means the space will be the same temperature as the rest of your home. The advantages of the unvented conditioned attic construction are increasingly being recognized within the industry to help with the following.

When all of the insulation is tight to the roof deck the unvented enclosed rafter truss assembly or unvented attic is within the building envelope and the attic will be conditioned to have a similar temperature as the interior space. This air seal will. Other reasons for constructing an unvented attic include the following. A conditioned attic requires a full commitment.

Mixing vented and unvented portions will lead to heavy condensation on the exposed roof sheathing. In most cases the existing insulation on an attic floor should be removed when an unconditioned attic is converted to a conditioned attic. Lstiburek s enthusiasm was rooted in his desire to bring attic ductwork inside a home s thermal envelope. However this recommendation should be addressed on a case by case basis.

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.