R-Value of Plywood Explained: Compare OSB, Sheetrock & More

Let’s not overcomplicate this—R-value is just a way to measure how well a material slows down heat from passing through it. The higher the number, the better it keeps your warm air inside in winter, or blocks heat from getting in during summer.

Think of it like the thermal version of a dam. Some materials are great at holding heat back. Others, not so much. And plywood? Well, it’s more of a speed bump than a brick wall regarding insulation.

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So, Does Plywood Insulate Much?

Not really. Plywood isn’t meant to insulate—it’s there for structure. But it does provide a little resistance to heat flow. When you’re doing the math on a wall’s total R-value, it’s worth counting.

The rule of thumb I go by is:

🔸 1 inch of plywood = R-value of about 1.25

It’s not huge, but it’s not nothing either. And when you start stacking layers—drywall inside, insulation in the stud bays, plywood or OSB outside—it adds up.

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R-Value of Plywood by Thickness (Real-World Numbers)

Here’s the chart I keep on my phone whenever I’m figuring up walls or helping friends with shop builds:

Plywood Thickness	Approx. R-Value
1/4″	0.31
3/8″	0.47
15/32″	0.59
1/2″	0.63
5/8″	0.77
3/4″	0.94
1″	1.25
1-1/8″	1.41

📥 Want this in your shop binder? Download the cheat sheet as a printable PDF

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How Plywood Stacks Up to OSB and Drywall (Literally)

OSB (Oriented Strand Board)

When I use OSB instead of plywood—usually on roof decks or subfloors—it gives me slightly less insulation per inch:

• 3/8″ OSB = R 0.45
• 7/16″ OSB = R 0.51
• 1/2″ OSB = R 0.74
• 3/4″ OSB = R 0.91

If you’re debating between plywood and OSB, insulation probably won’t be the deciding factor—it’s more about cost and structural needs. Here’s a more detailed comparison: OSB vs. Plywood

Drywall (a.k.a. Sheetrock)

Drywall, meanwhile, insulates even less. Half-inch drywall gives you about R 0.45. So plywood actually beats it there—but again, drywall’s not meant to keep you warm. It’s just a finishing layer.

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How to Figure Out a Wall’s Total R-Value (The Realistic Way)

Let’s say you’ve got a 2×4 wall:

• 1/2″ plywood outside = R 0.63
• R-13 fiberglass in the cavity = R 13.00
• 1/2″ drywall inside = R 0.45
  ➡️ On paper, that’s R 14.08

But in real life? Studs, air leaks, windows, outlet boxes—all of that reduces the effective R-value. I usually knock off about 10–15% to keep my expectations honest.

If you’re planning a build or remodel, I recommend reading our guide to Plywood Wall Sheathing for more detail on layering and wall strength.

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Particle Board R-Values (If You’re Dealing With It)

Older homes sometimes have particleboard underlayment under the floors or in weird places. It insulates a bit better than plywood per inch:

• 5/8″ particle board = R 0.82
• 1″ = R 1.31

Still not great, but worth noting if you’re trying to calculate insulation in existing walls or floors.

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Can R-Values Break Down Over Time? Absolutely.

I’ve opened walls in 30-year-old houses and seen insulation resembling crumpled tissue. Moisture, age, compression—it all eats away at effectiveness. That’s why old homes tend to feel drafty even if they technically have insulation.

What makes a difference:

• Water leaks (ruins batts fast)
• Compressed insulation behind paneling or boxes
• Drafty seams around windows, vents, and doors
• Gaps in attic hatches or wall penetrations

We break this down more in our Home Insulation  Tips article.

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Fastest DIY Upgrade: Seal the Air Leaks

You can blow thousands re-insulating your attic—or start with weather stripping and foam tape and feel an instant difference. I’ve used this stuff around garage doors and crawlspaces:

👉 Frost King Weatherseal Foam Tape – cheap, easy, surprisingly effective.

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Final Thoughts (From One Builder to Another)

Plywood isn’t your hero when it comes to insulation. But it plays a role—and when combined with fiberglass, foam, drywall, and siding, it’s part of the bigger energy-efficiency puzzle.

Quick recap:

• 3/4″ plywood = R 0.94
• Better than drywall, slightly better than OSB
• Always pair with real insulation

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Grab the Free Printable Chart

Want a copy of the R-value chart I use in the field?

👉 Click here to download the PDF – print it, laminate it, or tape it to the inside of your toolbox lid.