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「Plywood R-Value: Thermal Resistance by Thickness (and Why It's Not Insulation)」は日本語ではまだご利用いただけません

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Related Reading

Properties of plywoodThe broader properties overview that puts R-value alongside the panel's structural, moisture, and durability characteristics.
Density of plywoodThe paired density and weight reference that drives both the per-inch R-value figure and the panel's role in real wall assemblies.
Plywood span ratingThe APA span-rating companion — the structural property that should actually drive a sheathing thickness choice, not R-value.
23/32 vs 3/4 plywoodWhy nominal 3/4-inch sheathing measures 23/32-inch in real life, and what the difference means for stacking R-value figures by stated thickness.

Quick Answers

What is the R-value of plywood?
About 1.25 per inch of thickness. Common sheet thicknesses: 1/4" ≈ R-0.31, 3/8" ≈ R-0.47, 1/2" ≈ R-0.63, 5/8" ≈ R-0.77, 3/4" ≈ R-0.94, and 1" ≈ R-1.25. These are public reference figures from APA, PFS-TECO, and the Alaska Housing Finance Corporation manual.
Does plywood insulate a wall?
Not meaningfully. In a typical 2x6 code-built wall the plywood sheathing contributes about 5 percent of the assembly R-value. The cavity insulation (R-21 fiberglass batt or equivalent) does roughly 95 percent of the thermal work. Plywood is structural sheathing, not insulation.
What has more R-value, plywood or OSB?
OSB is slightly higher per inch — about 1.30 to 1.40 versus plywood's 1.25 — because the compressed strand mat is denser than cross-laminated veneer. The difference is small enough not to drive a real wall calculation. Choose between them on swelling behavior, nail-holding, and edge integrity, not on thermal resistance.
Does plywood have more R-value than drywall?
Yes. Plywood is about 1.25 R per inch, drywall about 0.45 R per inch. Solid wood sits in between at about 1.0 R per inch. None of the three is an insulation product — these are structural and finish materials.
What is plywood's k-value (thermal conductivity)?
About 0.12 W/(m·K) for typical softwood-faced cross-laminated plywood, the figure cited in EN ISO 10456 for wood-based panels. Denser plantation hardwood plywood (eucalyptus, acacia, hevea) runs slightly higher at 0.13 to 0.14 W/(m·K). The reciprocal of k gives R per unit thickness in SI units.