Energy Code Checker: Insulation Requirements by Address

Type your address (or pick your state and county) to find your IECC climate zone, choose the energy code edition from 2012 to 2024, and see the required insulation, window and air-leakage values on a house cross-section. Then enter your planned values to see what passes.

Each label shows the minimum R-value or maximum U-factor for your zone and edition · enter your planned values below and the labels turn green or red

1. Where is the house?

The address goes straight from your browser to the U.S. Census Bureau's free geocoder, which returns only your county. This site does not store it, and it is left out of the share link.

Why "IECC" and not "IBC"? The building codes (IRC for houses, IBC for larger buildings) do not write their own energy rules. They point to the International Energy Conservation Code, so the IECC edition is the thing to pick.

2. Your planned values optional, leave blank to skip

Enter what your plans or product labels say
R
R
R
R
R
R
R
R
ACH50
cfm/100 sq ft

The U-factor and SHGC are printed on the NFRC label on each window. R-value is printed on the insulation package. Leave a box blank to skip that part.

What the table asks for

—

Full requirements table every component, with pass or fail
ComponentRequiredYoursResult
Which code each state uses U.S. Department of Energy status, as of …
StateResidential energy codeEffective

Cities and counties can adopt a newer edition or add amendments, and some states let local governments decide. Always confirm with your building department.

Notes on reading the table
    How this checker works

    The table: the IECC residential chapter lists, for each climate zone, the minimum R-value of each assembly and the maximum U-factor and solar heat gain coefficient (SHGC) of windows and skylights. That is the prescriptive path. The 2012 edition prints it as Table R402.1.1, the 2015 and 2018 editions as Table R402.1.2, and the 2021 and 2024 editions as Table R402.1.3 (with the equivalent U-factors in R402.1.2). This tool reads the same rows and shows them on the cross-section.

    Climate zone: the IECC assigns a zone to every county (Table R301.1). The number runs from 1 (hot) to 8 (very cold) and the letter is the moisture class: A is humid, B is dry, C is marine. The map was redrawn for the 2021 edition, so this tool carries both: the 2012-2018 map for those editions and the 2021 map for the 2021 and 2024 editions. When you type an address, the U.S. Census Bureau geocoder returns your county and the tool looks it up in the right map. If your county is marked warm-humid in the code, basement and crawl-space wall insulation is not required in zone 3, and the tool applies that.

    Pass or fail: a ceiling, slab or window value passes when it equals or beats the table. Walls, floors, and basement or crawl-space walls pass when your cavity R and continuous R meet any one of the listed combinations. Window U-factor, SHGC, skylight U-factor, blower-door ACH50 and duct leakage pass when they are at or below the limit. A short value on the prescriptive path can sometimes be traded against a stronger part under the code's UA or performance paths, so treat "short" as a flag, not a verdict.

    Editions: IBC, IRC, IECC, 2026 and 2027

    Insulation, window and air-sealing rules for houses live in the International Energy Conservation Code (IECC). The International Residential Code (houses) repeats or points to them in Chapter 11, and the International Building Code (larger buildings) points to the IECC commercial provisions or ASHRAE 90.1. So this tool asks for an IECC edition.

    • Published editions covered: 2012, 2015, 2018, 2021 and 2024. There is no 2026 IECC.
    • 2027 IECC: the residential and commercial chapters finished the ICC development process in 2026 with no appeals filed, and publication is anticipated around December 1, 2026. It is not published yet, so no tables are included. This tool will need an update once it is.
    • Commercial: this tool covers houses and small residential buildings only. Commercial and larger multifamily buildings follow the IECC commercial chapter or ASHRAE 90.1.
    What changed between editions
    • 2012 to 2015: the prescriptive numbers in this tool are the same. 2015 added clearer wording and footnotes.
    • 2018: windows get tighter in zones 3 and up (U-0.32 in zones 3 and 4, U-0.30 in zones 5 to 8). Everything else matches 2015.
    • 2021: bigger jumps. Attics go to R-49 in zones 2 and 3 and R-60 in zones 4 to 8. Walls in zones 4 to 8 move to R-30 or a combination with foam sheathing. Slab edge insulation reaches 4 ft in zones 4 and up. The climate zone map changes for about 10 percent of counties.
    • 2024: the table is reorganized, with new rows for skylight SHGC, roof insulation entirely above the deck, floor insulation with foam options, and heated slabs. Attic requirements are R-38 in zones 2 and 3 and R-49 in zones 4 to 8. Windows get tighter in zones 5 to 8 (U-0.28 and U-0.27), and air-leakage limits change to 4, 3 and 2.5 ACH50 depending on zone. The county map is the same as 2021.
    Where this data comes from

    The requirement tables were read from the published IECC text and checked against a second state-published copy of each edition. County zones come from the U.S. Department of Energy's PNNL county data and were cross-checked against each edition's Table R301.1; where the data file and the printed table disagreed, this tool follows the printed table. The state code list is the U.S. Department of Energy Building Energy Codes Program status page. Everything is a planning aid: the adopted code text, local amendments and your building department decide what applies to your project.

    Sources

    Estimates only — not engineering, legal or code advice. Check requirements with your local building department and a licensed professional before you build.

    Common questions

    How does the address lookup find my climate zone?

    Your browser sends the address to the U.S. Census Bureau's free geocoder, which answers with your county. This tool then looks that county up in the IECC climate zone list (Table R301.1, using the county data published by the U.S. Department of Energy's PNNL lab). Climate zones are set county by county, so every address in a county gets the same zone. The address is not saved by this site and is never put in the share link. If the geocoder cannot match your address, pick your state and county by hand, or choose the zone yourself.

    Which energy code edition applies to my house?

    Your state or city decides, not the tool. The U.S. Department of Energy tracks each state's current residential energy code, and this tool starts the edition box on your state's code when it is an IECC edition: for example 2015 in Texas (with state amendments, effective Sept. 1, 2016), 2018 in Ohio, 2021 in Virginia and 2024 in Nevada. Some states have no statewide residential code, and many cities adopt a newer edition or add amendments. The City of Houston, for example, enforces the 2021 IECC with Houston amendments. Ask your building department which edition applies to your address.

    Is it the IBC or the IECC? Is there a 2026 edition?

    For energy, the building codes point to the International Energy Conservation Code (IECC). Houses fall under the International Residential Code (IRC), whose energy chapter (Chapter 11) mirrors or points to the IECC residential provisions. Larger buildings fall under the International Building Code, which points to the IECC commercial provisions or ASHRAE 90.1. There is no 2026 IECC. The editions are 2012, 2015, 2018, 2021 and 2024. The 2027 IECC has finished its development process but is not expected to be published until about December 2026, so it is not included here.

    Why does my climate zone change when I change the edition?

    The IECC climate zone map was redrawn for the 2021 edition, and the 2024 edition keeps that new map. About 10 percent of U.S. counties moved. The 2012, 2015 and 2018 editions use the older map. Example: Dallas County, Texas is zone 3A on the older map and 2A on the 2021 and 2024 map, while Harris County (Houston) is 2A on both. The tool picks the right map for the edition you choose and tells you when your county's zone differs between the two.

    How much attic insulation does zone 2 need?

    It depends on the edition. Zone 2 asks for R-38 in the 2012, 2015, 2018 and 2024 editions and R-49 in the 2021 edition. Zone 3 is also R-38 (2012, 2015, 2018, 2024) and R-49 (2021). Zone 1 is R-30 in every edition. Colder zones (4 to 8) ask for R-49 in 2012, 2015, 2018 and 2024 and R-60 in 2021. An R-38 attic can count as R-49 (and R-30 as R-38) when the insulation covers the whole attic floor out over the top of the wall at full, uncompressed height (IECC R402.2.1).

    What wall insulation and windows does zone 2 need?

    Zone 2 walls need R-13 in the cavity in 2012, 2015 and 2018, and R-13 in the cavity or R-10 continuous insulation in 2021 and 2024. Windows must be U-0.40 or lower with a solar heat gain coefficient (SHGC) of 0.25 or lower in every edition. Skylights are U-0.65 or lower in 2012 to 2021 and U-0.60 in 2024. Floors over unconditioned space need R-13. Zone 3 and colder zones ask for more: pick your zone above to see the exact numbers.

    What air leakage and duct testing does the code require?

    A blower-door test at the end of construction must stay under a limit that depends on edition and zone. In the 2012, 2015, 2018 and 2021 editions it is 5 air changes per hour at 50 pascals (5 ACH50) in zones 1 and 2 and 3 ACH50 in zones 3 to 8. The 2024 edition is 4 ACH50 in zones 1 and 2, 3 ACH50 in zones 3 to 5 and 2.5 ACH50 in zones 6 to 8. Ducts are tested too: total leakage of 4 cubic feet per minute or less per 100 sq ft of floor area, with a higher allowance when all ducts are inside the insulated shell in the 2021 and 2024 editions.

    Does an addition or remodel have to meet the same table?

    New construction and additions generally follow the prescriptive table for the new part. For alterations and repairs, existing parts you do not touch are not required to be upgraded, but new or replaced windows, framing cavities you open up and new ducts usually must meet current requirements. The rules vary by edition and by city, so ask your building department before you start.

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