Attic Conditioned Space

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 conditioned space.

Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts. Traditionally building codes have required attic ventilation. 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. In a roof attic assembly the builder has two choices.

An unvented attic assembly a k a. 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. Compact assembly or hot roof ventilated roof assembly.

If you planned to leave the open cell foam exposed to the attic it would certainly dry to the inside much more easily. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling. Well mainly it s a way to save space. However you do not describe the potential uses for that space and that gives me pause as to how to properly evaluate the risks of your options.

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. You can use rigid foam panels or do as tom silva does with nearly all houses these days. 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. 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.

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. An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan.