Conditioned Attic Space

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

Conditioned attic space.

An unvented attic assembly a k a. 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. 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. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling.

You can insulate the rafter space provided that you leave a ventilation space between the top of the insulation typically fiberglass batts or blown cellulose and the underside of the roof sheathing section r806 1 ventilation required. 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. 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. If you want the extra storage and don t want to take the risk of moisture buildup the unvented system is the best fit for your home.

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. Pull down stair or ladder. Add weatherstripping around the perimeter and a sweep to the door of a walk up attic. 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. Compact assembly or hot roof ventilated roof assembly. In warmer climates unvented attics can prevent the condensation that occurs on ductwork in some vented attic spaces. 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.