Conditioned Attic Space

Pull down stair or ladder.

Conditioned attic space.

In a roof attic assembly the builder has two choices. 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. 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. 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.

Attic hatch or door. Traditionally building codes have required attic ventilation. 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. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling.

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. An unvented attic assembly a k a. Add weatherstripping around the perimeter and a sweep to the door of a walk up attic. 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.

Compact assembly or hot roof ventilated roof assembly. 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. In warmer climates unvented attics can prevent the condensation that occurs on ductwork in some vented attic spaces. The intended purpose was to allow warm air and moisture to escape.