How to Insulate a Cabin Floor

Cabin in winter

The floor of a log or framed cabin is the thinnest area of the structure construction. Adding insulation to the cabin floor will provide a moisture and air barrier, making your cabin more efficient to cool during the hot summer months and to heat during the cold months of winter. Installing insulation can save several times more money in heating costs over the life of the cabin than the initial cost to install it. Cabins in cold climates will benefit the most, however. Even in moderate or damp climates, cabin floor insulation tis cost-effective.

Things You'll Need

• Tape measure
• Industrial shears or scissors
• Nails
• Hammer
• Polyethylene twine
• Bat insulation

Instructions

1. Do not insulate under your cabin unless the crawlspace is well ventilated. The crawlspace should have at least two vents to provide air circulation. If there is standing water in the crawl space, provide for adequate drainage before adding insulation. If insulating under an older cabin, check for termites or dry rot prior to installing new insulation. If these problems are evident, remedy them before adding insulation materials.

2. Fill floor cavities with insulation, filling all gaps. Fiberglass bats, with vapor barrier facing to cover the sub-floor area, are a simple way to fill these voids. Bats come in a variety of thickness: 8, 10 and 12 inches thick. Choose one that will supply the "R" value you desire. A minimum rating of R-19 is recommended by heating professionals. Position the bats in place and secure by stapling with recycled plastic straps. Insulation bats can also be held in place by polyethylene twine woven across the joists and held in position with nails, hooks or screws. Insulation manufacturers also make a plastic mesh that can be cut to size and screwed to the floor joists to hold the insulation bats in place. Polyethylene is recommended as it is resistant to moisture, insects and rodents.

3. Add perimeter insulation around the interior of the foundation. Foam board, with a moisture absorption rating of less than 3 percent, cut to size, will provide an effective air and moisture barrier. Insert the cut pieces around the foundation and cut to fit between the floor joists under the sub-floor. Nail or glue insulation in place.

Tips & Warnings

• Wear a hard hat, gloves and protective ear and eye gear when working with insulation materials.

References

• Logspan: Floor and Roof Insulation
• Oikos: Filling a Floor With Bat Insulation
• Bonneville Power Administration: Energy Efficiency