R-Value Calculator
Select your climate zone and building location to look up the DOE-recommended R-value. Use the layering tool below to calculate a combined R-value for multiple insulation layers.
R-Value Lookup
Source: ENERGY STAR / U.S. DOE recommended R-values for existing homes, as of June 2026.
R-Value Layer Calculator
Add multiple insulation layers to find a combined R-value.
DOE Recommended R-Values — All Zones
Source: ENERGY STAR / U.S. DOE — as of June 2026. These are recommended ranges for existing-home upgrades. New construction follows IECC code minimums.
| Climate Zone | Attic / Ceiling | Exterior Wall | Floor / Crawl Space |
|---|---|---|---|
| Zone 1 — Hottest | R-30 | R-13 | R-13 |
| Zone 2 — Hot | R-30–49 | R-13–15 | R-13–19 |
| Zone 3 — Warm | R-30–49 | R-13–15 | R-19–25 |
| Zone 4 — Mixed | R-38–60 | R-13–21 | R-25–30 |
| Zone 5 — Cool | R-49–60 | R-13–21 | R-25–30 |
| Zone 6 — Cold | R-49–60 | R-15–21 | R-25–30 |
| Zone 7 — V. Cold | R-49–60 | R-18–21+ | R-25–30 |
| Zone 8 — Subarc. | R-49–60 | R-18–21+ | R-25–30 |
Wall values are for cavity insulation; add continuous exterior insulation (CI) for full code compliance in Zones 4+. Verify with your local building department and energy.gov.
Related Calculators
Frequently Asked Questions
R-value measures thermal resistance — how strongly a material resists heat flow through it. A higher R-value means better insulation. The U.S. DOE specifies minimum recommended R-values by climate zone and location in the home (attic, wall, floor, crawl space).
For exterior walls in Climate Zone 5, the DOE recommends R-13 to R-21 in wall cavities, or R-13 + R-5 continuous insulation (CI) on the exterior. Standard 2×4 framing with R-15 batts meets code minimum for many Zone 5 locations. Source: energy.gov — as of June 2026.
R-values are additive. If you have R-11 existing batts and add R-30 blown-in on top, your total attic R-value is R-41. The calculator on this page adds layers for you.
Slightly. R-value ratings are measured at 75°F (24°C) mean temperature per ASTM C518. In very cold conditions, some materials (especially open-cell spray foam) can perform slightly differently, but for practical planning the labeled R-value is the right number to use.
The U.S. Department of Energy publishes recommended R-value tables at energy.gov/energysaver/insulation and ENERGY STAR maintains a companion guide at energystar.gov. Our reference table on the Climate Zones page reproduces the recommended ranges from these sources as of June 2026.