Attic Conditioned Space

Traditionally building codes have required attic ventilation.

Attic conditioned space.

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. In warmer climates unvented attics can prevent the condensation that occurs on ductwork in some vented attic spaces. Though it s against building code to vent any kind of exhaust to an attic space many home builders have gotten away with this shortcut. 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.

Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts. In a roof attic assembly the builder has two choices. Compact assembly or hot roof ventilated roof assembly. So why put an hvac system up in the attic at all.

The intended purpose was to allow warm air and moisture to escape. 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. You can use rigid foam. If you re considering turning your attic into conditioned storage or living space it s worth changing tactics to insulate between the rafters and wall joists instead of the floor.

In the winter any small air leaks in the attic probably not through the foam but elsewhere leak air out and the warm humid air from the conditioned space refills the attic providing a fresh supply of humidity that can replenish the reservoir of humidity in the roof deck. 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. Attic hvac systems save space. 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. Well mainly it s a way to save space.