Attic Space

A home may have a sound structure, high insulation levels, and a solid foundation, but if it does not have a continuously sealed whole-house draft barrier, the potential energy savings will be diminished. A whole-house draft barrier is a continuously connected layer of solid or air-tight materials that block air flow, moisture, and pests from entering the conditioned space of a home. One example of an air barrier is the drywall on the home’s walls and ceilings, when the seams are taped and mudded and caulk, spray foam, or gaskets are used to seal around wiring, plumbing, ducts, etc. The wall and ceiling insulation should be in full contact with this air barrier layer.

Knee walls, the walls that separate conditioned from unconditioned space in an attic, can be a source of significant air leakage if a continuous air barrier is not provided to prevent unconditioned air from flowing under the knee wall and under the floor boards of the attic room. There are two ways to block off this air flow: either a continuous air barrier can be provided from the top of the knee wall down to the attic floor, including the spaces between the attic floor joists from the bottom of the knee wall to the ceiling deck below, or a continuous air barrier can be installed from the top of the knee wall along the attic roofline to the top plate of the home’s exterior wall. With either method the air barrier should be installed before installing attic floor insulation to the unconditioned portion of the attic. An air barrier is defined as any durable, solid material that blocks air flow between conditioned space and unconditioned space, including necessary sealing to block excessive air flow at edges and seams and adequate support to resist positive and negative pressures without displacement or damage. Air barrier material can include thin sheet goods such as rigid insulation, dry wall, OSB, plywood, or rolled batt insulation that is covered with spray foam. These materials may be installed by insulators, framers, or drywallers. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site.