Insulation R-Value Calculator by Climate Zone
Pick your climate zone and attic to see the R-value ENERGY STAR recommends to add in an existing home.
Sample choice, to show how it works. Pick your own zone.
Choose your climate zone. The ENERGY STAR map linked under the field shows it.
This is an estimate, not a professional calculation. See the disclaimer and the methodology.
How it is calculated
R-value measures how well insulation resists heat flow: the higher the number, the better it insulates. Insulation levels are specified by R-value.
This is a lookup, not a calculation. It returns the levels in the ENERGY STAR table of recommended insulation levels for retrofitting existing wood-framed buildings, which is 2021 International Energy Conservation Code (IECC) Residential Provisions Chapter 4 Table R402.1.3. The table gives levels for the attic, with two cases (no insulation, or about 3 to 4 inches), and for the floor.
The ENERGY STAR page groups some zones: 4A and 4B share levels, as do 4C, 5 and 6, and 7 and 8. The dropdown follows the same groups.
For walls, the ENERGY STAR page gives guidance in words: adding insulative sheathing under new siding for an above-ground wall, and sheathing or a batt for a basement or crawl space wall. We show it as printed. The page gives no wall guidance for zones 1 and 2.
The zone is not worked out from your address. The ENERGY STAR page shows a map, and the dropdown links to it. If your home is near a border, ask a local contractor or your building department, because local code can ask for more.
The levels are for adding to an existing home. They are not an energy audit and do not tell you how many inches that is for a product, because each product has its own R-value per inch.
Worked examples
Uninsulated attic in zone 1
Zone 1 with an uninsulated attic: R30 in the attic and R13 for the floor.
An attic with 3 to 4 inches in zone 3
Zone 3 with about 3 to 4 inches today: R38 in the attic and R19 for the floor. For an uninsulated wall, ENERGY STAR says: add r5 insulative wall sheathing beneath the new siding.
A cold zone
Zones 7 and 8 with an uninsulated attic: R60 in the attic and R38 for the floor.
Frequently asked questions
What R-value do I need in my attic?
It depends on your climate zone and on how much insulation you have. Pick both and the lookup shows the ENERGY STAR level for an existing home.
How do I find my climate zone?
ENERGY STAR shows a map of the zones on its insulation page, which the dropdown links to. We do not look a zone up from an address, because we found no official list by county that we could verify.
What does R-value mean?
It is the resistance to heat flow. A higher R-value means more insulation. ENERGY STAR specifies insulation levels by R-value.
Are these the levels for a new house?
No. They are ENERGY STAR levels for retrofitting existing wood-framed buildings. New houses follow the building code of the place, which can differ.
Why is there no wall value for zones 1 and 2?
The ENERGY STAR page gives wall guidance only for zone 3 and colder zones. We do not add a value it does not give.
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Sources and last update
Last updated: November 3, 2026. See methodology and sources.