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.

Attic conditioned space.

Well mainly it s a way to save space. Traditionally building codes have required attic ventilation. An unvented attic assembly a k a. You can use rigid foam.

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

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. 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. 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. 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.

Attic hvac systems save space. Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling. An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan.

Compact assembly or hot roof ventilated roof assembly. 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.