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Insulation R-Value Calculator
Target R-value by IECC climate zone and thickness needed across 5 insulation materials.
Updated April 2026
Insulation R-Value Calculator
Find the IECC-recommended R-value for your climate zone and the thickness needed in common insulation materials.
Recommended R-valueR-38
You currently haveR-0
Gap to closeR-38
| Material | R/inch | Total thickness | Add to reach target |
|---|---|---|---|
| Fiberglass batt | 3 | 12.7" | 12.7" |
| Blown cellulose | 3.7 | 10.3" | 10.3" |
| Closed-cell spray foam | 6.5 | 5.8" | 5.8" |
| Rigid foam board (XPS) | 5 | 7.6" | 7.6" |
| Mineral wool batt | 3.3 | 11.5" | 11.5" |
Target values reflect 2021 IECC residential recommendations. Ensure proper air sealing and vapor retarder placement before adding insulation — a leaky envelope undermines R-value gains.
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What it does
IECC-recommended R-values by zone (hot south vs very cold north) plus the thickness for fiberglass, cellulose, spray foam, rigid foam.
Runs entirely in your browser — no upload, no account, no watermark. For more tools in this category see the full tools index.
Embed this tool on your siteShow snippetHide
Paste this snippet into any page. Loads on-demand (lazy), no tracking scripts, and sized to most dashboards. Replace the height to fit your layout.
<iframe src="https://freetoolarena.com/embed/insulation-r-value-calculator" width="100%" height="720" frameborder="0" loading="lazy" title="Insulation R-Value Calculator" style="border:1px solid #e2e8f0;border-radius:12px;max-width:720px;"></iframe>How to use it
- Pick climate zone + area.
- Enter current R-value.
- Read thickness by material.
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