EPA's ENERGY STAR program recommends R49 to R60 in an uninsulated attic for most U.S. climate zones. And EPA estimates that air sealing plus insulation saves an average of 15% on heating and cooling costs.
So EPA's guidance has two parts: how much insulation to add, and what it can save. Here's what ENERGY STAR's pages showed on October 9, 2026.
What Insulation Levels Does EPA Recommend?
ENERGY STAR's table, based on the 2021 International Energy Conservation Code, recommends R30 to R60 for an uninsulated attic, R25 to R49 for an attic that already has 3 to 4 inches, and R13 to R38 for floors, rising with colder climate zones.
| Climate zone (IECC) | Attic, uninsulated | Attic, already 3–4 in. | Floor |
|---|---|---|---|
| 1 | R30 | R25 | R13 |
| 2 | R49 | R38 | R13 |
| 3 | R49 | R38 | R19 |
| 4A and 4B | R60 | R49 | R19 |
| 4C, 5 and 6 | R60 | R49 | R30 |
| 7 and 8 | R60 | R49 | R38 |
ENERGY STAR says these are the levels that are cost-effective for different climates and locations in the home, for retrofitting existing wood-framed buildings. The insulation R-value chart explains how to read the table.
What Does EPA Recommend for Walls and Basements?
When exterior siding comes off, ENERGY STAR recommends blowing insulation into empty wall cavities and adding R5 sheathing in Zone 3, or R5 to R10 in Zones 4 to 8. For basement or crawlspace walls, it recommends R5 sheathing or R13 batt in Zone 3, rising to R15 sheathing or R19 batt in Zones 4C to 8.
For an already-insulated 2x4 wall in Zones 4 to 8, ENERGY STAR recommends adding R10 insulative sheathing beneath the new siding.
How Much Does EPA Say Insulation Saves?
EPA estimates that homeowners can save an average of 15% on heating and cooling costs, or an average of 11% on total energy costs, by air sealing their homes and adding insulation in attics, floors over crawl spaces and basements, according to ENERGY STAR.
ENERGY STAR also says 9 out of 10 U.S. homes are under-insulated. The air sealing savings guide covers the sealing half of that estimate.
Has the Federal Insulation Tax Credit Ended?
Yes, for 2026 projects. The federal 25C credit, which covered insulation, ended for property placed in service after December 31, 2025, according to IRS Fact Sheet FS-2025-05. Older pages that describe it as running for years more are out of date.
Insulation installed during 2025 can still go on the 2025 return. For 2026, utility programs such as LADWP's attic insulation rebate are what lower the cost; the California insulation rebates guide lists them.
Official Sources
The R-values and savings estimate on this page come from ENERGY STAR's own pages, checked on October 9, 2026.
- ENERGY STAR: Recommended Home Insulation R-Values, the R-value table and wall guidance
- ENERGY STAR: Why Seal and Insulate?, EPA's 15% / 11% savings estimate
- IRS FS-2025-05, the IRS table showing when each federal credit ended
Frequently Asked Questions
What R-value does the EPA recommend for an attic?
ENERGY STAR's table recommends R30 in Zone 1, R49 in Zones 2 and 3, and R60 in Zones 4 to 8 for an uninsulated attic. If the attic already has 3 to 4 inches of insulation, the targets are R25, R38 and R49, based on the 2021 IECC.
Does EPA say insulation lowers energy bills?
Yes. EPA estimates that air sealing plus adding insulation in attics, floors over crawl spaces and basements saves an average of 15% on heating and cooling costs, or 11% on total energy costs, according to ENERGY STAR's Why Seal and Insulate page.
Did the federal insulation tax credit end?
Yes. The federal 25C credit ended for property placed in service after December 31, 2025, according to IRS Fact Sheet FS-2025-05. Because it ended, insulation installed in 2026 gets no federal credit; work completed in 2025 is claimed on the 2025 return.
Insulating in 2026? See the verified rebates for your address with the free rebate calculator.