Interior Basement wall insulation Stratagies Improvements

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INTERIOR BASEMENT WALL INSULATION STRATEGIES

Disadvantages of basement wall insulation include:

• Costs may exceed those for insulating the basement ceiling, depending on the materials and approach selected.

• If the surrounding soil contains radon gas, the home will require a mitigation system underneath the basement floor.

• In termite-prone areas, exterior foam insulation in ground contact allows a path for termites to access the walls of the home undetected. Check with local code officials to determine acceptance of exterior foam application. Some installations will require non-invasive termite detection systems, such as termite baits. One of the nation’s leading foam insulation manufacturers has released a rigid foam with borate insect repellent.

BASEMENT INSULATION TECHNIQUES
Basement insulation levels should be selected in accordance with the International Energy Conservation Code or DOE Insulation Fact Sheet (DOE/CE-0180), which can be obtained from DOE or the web at www.ornl.gov/roofs+walls. Be sure to insulate both the masonry and stud walls of daylight basements.

There are three primary ways to insulate the masonry portion of a basement wall:

1. Exterior insulation—1 to 3 inches are recommended for most climate zones.
Extruded polystyrene (R-5 per inch) is durable and moisture resistant. Expanded polystyrene (R-4 per inch) is less expensive, but it has a lower insulating value. Highdensity, drainable, fiberglass insulation or fiberous drainboard does not insulate as well as foam but provides a drainage plane. Leave a 6-inch gap between the insulation and wood foundation elements to provide a termite inspection area. Insulate rim joists.

2. Interior insulation—usually installed behind interior framing or with furring strips placed against the foundation wall (see figure on page 3). Joints and penetrations through the drywall must be well sealed to prevent movement of moisture laden air into the insulation and possible condensation. Insulate rim joists.

3. Insulated Concrete Forms—comparatively new products that are relatively easy to install. Once the hollow foam blocks are stacked, the cores are filled with concrete.

Most products provide continuous insulation on the interior and exterior. They also provide surfaces for attaching drywall, brick ties, and other finish materials. Many new insulated concrete forms are treated with termite-resistant chemicals. Insulate rim joists.

RADON CONTROL IN BASEMENTS
Radon is a radioactive gas that occurs in some soils. It can enter a home through the foundation and floor system. If it occurs in concentrations greater than 4 pico-curies per liter, it may pose a health risk to the home occupants.

To guard against radon problems:

• Install a 4-inch or greater gravel base with a continuous layer of 6-mil polyethylene on top of the gravel.

• Embed a “T” fitting attached to a 3-inch or larger diameter gas-tight pipe through the polyethylene barrier into the sub-slab aggregate before the slab is poured.

• Pour the slab and seal all slab joints and penetrations.

• Extend the gas-tight pipe vertically through an interior wall and terminate it at least 12 inches above the roof.

• Have an electrician stub-in a junction box in the attic.

• After construction is complete, test the basement for radon with an EPA-listed radon test kit, or hire a qualified technician. If the test shows concentrations above 4 picocuries per liter, install a small blower to the pipe in the attic to depressurize the sub-slab space. If use of the blower does not reduce radon levels below 4 pico-curies per liter, consult with local radon experts. For more detailed instructions, visit the EPA radon web site http://www.epa.gov/iaq/radon/.