Conditioned Attic Space

An unvented attic assembly a k a.

Conditioned attic space. The thermal boundary can be at the ceiling plane leaving the attic space above uninsulated and vented or the thermal boundary can be located at the roof line creating a sealed insulated conditioned or semi conditioned attic space. Pull down stair or ladder. A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic. Making the attic a conditioned space taking the building envelope to the roof is a good approach and will save energy another approach is to use radiant coated deck sheathing seal all ceiling attic penetrations and blow in r 60 insulation as it will cost less than spray foam and should give at least the same energy efficiency to the home.

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 attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling. Affix rigid foam insulation to the attic side of the hatch or door. Use a zippered insulated tent to keep the enclosure draft free attic tent at 7 attic cover insulator 120.

Choosing a conditioned attic vs unconditioned attic space comes down to what you want to do with the area and what works best with the design of your home. In a roof attic assembly the builder has two choices. In warmer climates unvented attics can prevent the condensation that occurs on ductwork in some vented attic spaces. The loss of energy efficiency means some designers choose to move the ductwork into the conditioned areas of the home and leave the attics unvented.

Attic hatch or door. Traditionally building codes have required attic ventilation. Add weatherstripping around the perimeter and a sweep to the door of a walk up attic. Compact assembly or hot roof ventilated roof assembly.