How much insulation do I need?
Enter your ZIP code to get the R-values recommended for your climate zone, how many inches of each material that means, and what an upgrade costs — plus the federal tax credit and rebates. Free, instant, no signup.
Short answer
Recommended insulation depends on your climate zone. Attic R-values rise from about R30–R49 in the warm South to R60 in the cold North; walls R13–R30; floors R13–R38. R-49 is about 19.6 inches of blown fiberglass or 7.5 inches of closed-cell foam. The federal 25C credit covers 30% of insulation materials, up to $1,200/yr.
Attic (cold)
R60
zones 4–8
Attic (warm)
R30–49
zone 1
R-49 fiberglass
~19.6"
blown-in
25C credit
30%
up to $1,200/yr
Recommended R-values by climate zone
| Climate zone | Attic / ceiling | Exterior walls | Floors | Crawlspace / basement wall |
|---|---|---|---|---|
| Zone 1 | R30–R49 | R13–R15 | R13 | Not required |
| Zone 2 | R49–R60 | R13–R21 | R13–R19 | Not required |
| Zone 3 | R49–R60 | R20–R21 | R19–R25 | R5 |
| Zone 4 | R60 | R20–R30 | R25–R30 | R10 |
| Zone 5 | R60 | R20–R30 | R30 | R15–R19 |
| Zone 6 | R60 | R20–R30 | R30 | R15–R19 |
| Zone 7 | R60 | R20–R30 | R38 | R15–R19 |
| Zone 8 | R60 | R20–R30 | R38 | R15–R19 |
ENERGY STAR–style recommended ranges for existing wood-frame homes. Zone 1 is South Florida; Zone 8 is arctic Alaska — enter your ZIP in the calculator to get your zone. Higher targets in a range assume you're also air-sealing.
Insulation tax credit & rebates
Federal 25C tax credit
The Energy Efficient Home Improvement Credit gives you 30% back on insulation and air-sealing materials, up to a combined $1,200 per year (shared with other improvements like windows and doors). Materials only — labor for insulation isn't eligible. In effect 2023–2032; claim it on IRS Form 5695.
Home Efficiency Rebates (HOMES)
Whole-home efficiency upgrades including insulation and air sealing.
Insulation: Up to $1,600 (higher for larger modeled energy savings; scales with household income)
All income levels; larger rebates for low- and moderate-income households
Home Electrification & Appliance Rebates (HEAR)
Insulation, air sealing, and ventilation as part of electrification.
Insulation: Up to $1,600 for insulation/air-sealing/ventilation
Low- and moderate-income households (under 150% of area median income)
IRA rebate programs are administered by each state and rolling out on their own timelines. Find your state's current status via the official DOE rebate finder. Incentive details last verified 2026-07-07; verify current rules before you buy or file — this is general information, not tax advice.
Insulation thickness by material
Insulation requirements by state
How we calculate this
Every number on this page comes from the same data the calculator uses — the published climate-zone recommendations plus each material's measured R per inch:
- Climate zone. your ZIP code maps to an IECC/DOE climate zone (1–8), which sets the recommended R-value range for attic, walls, floor, and crawlspace (the table above).
- Inches of material. target R-value ÷ the material's R per inch — blown fiberglass is R-2.5 per inch where closed-cell spray foam is R-6.5, so the same R-49 attic is ~20″ of one and ~8″ of the other.
- Cost. area × target R × the material's cost per sq ft per R-point, with a labor multiplier for professionally-installed figures (spray foam is normally quoted installed).
- Savings and credit. estimated annual savings follow EPA guidance (air-sealing + attic insulation ≈ 15% of heating/cooling costs), and the federal 25C credit covers 30% of insulation material cost up to $1,200/year.
Assumptions
- Existing wood-frame home; new construction and mass walls follow different code tables.
- R-values assume proper installation — compressed batts and gaps lose real-world R.
- Cost ranges are planning figures — spray foam and dense-pack quotes vary widely by market.
Sources
Last reviewed: July 13, 2026
Related tools
Frequently asked questions
How much insulation do I need for my house?
It depends on your climate zone. In the U.S., the DOE recommends roughly R30–R60 in the attic (more in colder zones), R13–R30 in exterior walls, and R13–R38 in floors over unconditioned space. Enter your ZIP above to see the exact recommended R-values for your zone and how many inches of each material that takes.
What R-value do I need in my climate zone?
The U.S. is divided into IECC climate zones 1 (hot, e.g. South Florida) through 8 (subarctic Alaska). Attic recommendations rise from about R30–R49 in zone 1 to R60 in zones 4–8. The calculator maps your ZIP to its zone and shows the attic, wall, floor, and crawlspace R-values recommended there.
How many inches of insulation is R-49?
It depends on the material. R-49 is about 19.6 inches of blown-in fiberglass, 14 inches of blown-in cellulose, or 7.5 inches of closed-cell spray foam, since each adds a different R-value per inch. The calculator converts any recommended R-value into inches for nine common materials.
Is there a tax credit for adding insulation?
Yes. The federal 25C Energy Efficient Home Improvement Credit covers 30% of insulation and air-sealing materials, up to a combined $1,200 per year (labor for insulation is not eligible). IRA HOMES/HEAR rebates administered by each state can add up to $1,600 more. See the incentives section below.
Where should I add insulation first?
The attic, almost always. It is the largest heat-loss surface, the cheapest to insulate (blown-in over the existing layer), and usually the most cost-effective upgrade. Air-sealing gaps before adding insulation makes it work far better.