Unvented Conditioned Attic

The intended purpose was to allow warm air and moisture to escape.

Unvented conditioned attic.

Energy conservation moisture management. Adding unvented attic insulation like spray foam seals the building envelope and stops airflow. Unvented conditioned attics were quite rare before the 1980s. Making the attic a conditioned space means the space will be the same temperature as the rest of your home.

To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents soffits etc which make it difficult to achieve an airtight ceiling plane. 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. Among the early promoters of conditioned attics was joe lstiburek a principal of the building science corporation.

Depending on the climate and the thickness of the existing insulation it may make sense to leave the old insulation in place. 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. This air seal will. Traditionally building codes have required attic ventilation.

Unventilated attics are common where roof assemblies are complex and it s difficult to create a sealed ceiling plane. This system can help you avoid. 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. Other reasons for constructing an unvented attic include the following.

Poorly insulated ducting can cause heat loss in colder months and the loss of conditioned air in the summer in vented attics. A conditioned attic requires a full commitment. Mixing vented and unvented portions will lead to heavy condensation on the exposed roof sheathing. This sheathing is less than a year old.

The advantages of the unvented conditioned attic construction are increasingly being recognized within the industry to help with the following.