Missouri REScheck Requirements (2026)

Key facts:

• No Statewide Energy Code — Local Adoption Only

• Kansas City: 2021 IECC

• St. Louis City: 2018 IECC

• Climate Zones 4A & 5A

 

REScheck may be required in Missouri for: new residential construction in adopting jurisdictions, additions/alterations where local code applies, conditioned structures in Kansas City/St. Louis/Columbia/Springfield, or wherever the local permit office requests documentation. Always verify the specific energy code — and whether one even exists — with the local permit office. Rural Missouri projects may have no energy code requirements at all.

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⚠ Missouri Has No Statewide Residential Energy Code: Missouri is one of approximately seven states that has never adopted a mandatory statewide residential energy code. Only the Missouri General Assembly can enact statewide code legislation, and it hasn't. Energy codes are adopted and enforced locally only: Kansas City enforces the 2021 IECC, St. Louis City enforces the 2018 IECC, many suburbs/rural communities are on older editions, and a significant number of counties have adopted no energy code at all.

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How Missouri Code Adoption Works

• No state agency is authorized to adopt or update residential energy codes

• Only the Missouri General Assembly can enact statewide code legislation — it has not done so for residential buildings

• All local jurisdictions except Class III counties may adopt their own energy codes

• Jurisdictions that don't adopt a code have no energy code requirements for private construction

• Missouri communities tend to adopt codes on a 6-year cycle, not the ICC's 3-year cycle

• State-funded buildings must meet the most recent IECC — but this doesn't apply to private residential construction

 

⚠ Legislative Threat to Watch (2025–2026): HB 939, introduced in the 2025 session, would prohibit any county or municipality from maintaining energy standards exceeding the 2009 IRC or 2009 IECC — effectively rolling back Kansas City's 2021 IECC, Columbia's 2018 IECC, and St. Louis City's 2018 IECC to 2009-era standards. It cleared House committees and got initial House approval but didn't pass in 2025. A similar bill has been refiled for 2026. Always verify current local code status before starting a project.

 

Energy Code Status by Major Jurisdiction

Jurisdiction  ·  Current Code  ·  Effective Date  ·  REScheck Accepted?

• Kansas City (KCMO):  2021 IECC + local KCBRC amendments   —   July 1, 2023 (mandatory Sept. 29, 2023)   —   Yes — 3 ACH50 blower door mandatory

• City of St. Louis:  2018 IECC + local amendments   —   Adopted; verify current date with city   —   Yes — verify local blower door requirement

• Columbia:  2018 IECC   —   Adopted; verify with Columbia Building Inspections   —   Yes

• Springfield:  Local IRC/IECC — verify current edition   —   Verify with Building Development Services   —   Likely yes — verify

• Independence:  Local adoption — verify current edition   —   Verify with Independence Building Inspections   —   Likely yes — verify

• St. Louis County (unincorporated):  2015 IECC (confirm update status)   —   Verify with County Building Division   —   Yes

• Most rural counties:  No energy code adopted, or older editions   —   N/A   —   Verify with local permit office

 

Critical Rule for Missouri Builders: Never assume a jurisdiction has adopted an energy code without verifying. Never assume a jurisdiction that previously had a code is still on the same edition — Missouri municipalities adopt infrequently and can be years or decades behind. The only reliable source is a direct call or email to the local permit office.

 

Kansas City 2021 IECC Requirements

Kansas City adopted the 2021 IECC effective July 1, 2023, with a 90-day grace period ending September 29, 2023 — the first Missouri jurisdiction on the 2021 edition. KCMO maintains its own Building and Rehabilitation Code (KCBRC) with local amendments.

• Ceilings: R-49 (R-38 satisfies at eave condition)

• Wood Frame Walls: R-20 cavity-only OR R-13+5ci

• Floor: R-19

• Basement Walls: R-10/13; Crawlspace Walls: R-10/13; Slab Edge: R-10 at 2 ft

• Windows: max U-0.32; SHGC: max 0.40

• Blower Door: 3 ACH50 mandatory — no visual inspection alternative under 2021 IECC

• Duct leakage: 4 CFM25/100 sq ft outside envelope; 8 CFM25/100 sq ft total

 

KCBRC Information Bulletin IB171 is the required submittal checklist for 2021 IECC compliance documents — contact Kansas City City Planning & Development for current local amendments before submittal.

 

St. Louis City 2018 IECC Requirements

The City of St. Louis (an independent city, separate from St. Louis County) has adopted the 2018 IECC with local amendments.

• Ceilings: R-49 (R-38 eave exception applies)

• Wood Frame Walls: R-20 cavity-only OR R-13+5ci

• Floor: R-19; Basement Walls: R-10/13; Crawlspace Walls: R-10/13; Slab Edge: R-10 at 2 ft

• Windows: max U-0.32; SHGC: max 0.40

• Verify blower door vs. visual inspection and duct leakage requirements with City of St. Louis Building Division

 

St. Louis Metro Complexity: The City of St. Louis (2018 IECC) is separate from St. Louis County, which contains 80+ municipalities (Clayton, Kirkwood, Webster Groves, Chesterfield, etc.) each potentially on a different code edition. Some County municipalities are on 2015 IECC, others earlier, some with no code at all. MWALLIANCE (mwalliance.org) maintains a city-by-city code list.

 

Missouri Climate Zones

Zone  ·  Coverage  ·  Classification  ·  Key Code Differences

• 4A:  Most of Missouri — Kansas City, St. Louis, Springfield, Columbia, Joplin, Jefferson City, Cape Girardeau   —   Mixed-Humid   —   Ceiling R-49 (2021/2018 IECC); wall R-20 or R-13+5ci; SHGC 0.40; window U-0.32; slab R-10 at 2 ft

• 5A:  Northern Missouri — Kirksville, Macon, Hannibal, Moberly, Brookfield areas   —   Cool-Humid   —   Stricter wall insulation (continuous insulation on prescriptive 2021 IECC path); floor R-30; no SHGC restriction; deeper slab depth

 

Zone Matters Even Without a Code: Even where no local code is adopted, the IECC climate zone assignment still matters for REScheck, which requires a climate zone to calculate trade-offs. Use Zone 4A for the vast majority of Missouri projects; Zone 5A for northern counties.

 

Is REScheck Required in Missouri?

• Kansas City (KCMO): always required under 2021 IECC

• City of St. Louis: required under 2018 IECC

• Columbia: required under 2018 IECC

• Any jurisdiction that has adopted an IECC edition and requires permit documentation

 

Rural Missouri: Many counties have adopted no energy code — REScheck may not be required, but verify with the local permit office, since some rural jurisdictions have adopted codes without advertising the fact.

 

Missouri-Specific Notes

• REScheck accepted wherever an IECC-based code has been adopted

• Code year to select depends on the local edition: 2021 IECC for Kansas City; 2018 IECC for St. Louis City and Columbia

• Missouri communities adopt on a 6-year cycle — adjacent municipalities may be on very different editions

• State-funded buildings must meet the most recent IECC even where no local code exists

• Class III counties do not have the right to adopt energy codes — projects there are effectively unregulated for energy

 

Common REScheck Considerations in Missouri

Kansas City Area

• Wrong code year — Kansas City is 2021 IECC, not 2018; adjacent Johnson County KS suburbs may differ

• Missing Kansas City local amendments (KCBRC, Information Bulletin IB171)

• Blower door compliance — 3 ACH50 mandatory; builders new to KC from no-code areas may lack testing infrastructure

• Zone 4A/5A confusion for northern suburbs (Clay, Platte, Clinton counties border Zone 5A)

• Duct leakage documentation — 2021 IECC tests even conditioned-space ducts, unlike pre-2021 practice

 

St. Louis Area & Statewide

• City vs. County code confusion — City of St. Louis (2018 IECC) vs. unincorporated County (2015 IECC) vs. individual municipalities

• No code = no documentation required in many jurisdictions, though voluntary IECC compliance is recommended for performance and appraisal value

• Code edition mismatch when relocating from no-code rural markets to Kansas City or St. Louis

• HB 939 uncertainty — monitor legislative outcomes for multi-year projects

• State buildings vs. private construction — stricter code applies only to publicly funded projects

 

Major Cities and Jurisdictions

Kansas City Metro (Zone 4A)

The only major Missouri jurisdiction confirmed on the 2021 IECC. The metro extends into Kansas — Johnson County, KS suburbs (Overland Park, Olathe, Lenexa) are generally on the 2021 IRC with their own history. Missouri-side suburbs (Independence, Blue Springs, Lee's Summit, Raytown) each maintain separate adoptions — verify each.

 

Springfield & Greene County (Zone 4A)

Missouri's third-largest city, commercial center of the Ozarks. Local codes adopted but editions/amendments vary — verify with Building Development Services.

 

St. Louis Metro (Zone 4A)

One of the country's most complex municipal code environments — 80+ municipalities in St. Louis County alone. O'Fallon and Wentzville in St. Charles County are among the fastest-growing markets and deserve separate verification.

 

Columbia & Mid-Missouri (Zone 4A)

Home to the University of Missouri, adopted the 2018 IECC and actively enforces it — one of the more progressive energy code markets in the state. A DOE study found Columbia's code adoption coincided with only a brief permit dip followed by a 49% increase, cited as evidence against HB 939's argument that energy codes suppress construction.

 

Frequently Asked Questions

Does Missouri have a statewide energy code?

No. Missouri is one of about seven states with no mandatory statewide residential energy code. Only the General Assembly can enact one, and it hasn't for residential buildings. Codes are adopted and enforced entirely at the local level; many rural counties have none at all.

 

Is REScheck required in Missouri?

Depends entirely on the jurisdiction. Required in Kansas City (2021 IECC), City of St. Louis (2018 IECC), and Columbia (2018 IECC). Not required where no energy code has been adopted, which includes many rural counties. Always verify with the local permit office.

 

What energy code does Kansas City use?

The 2021 IECC, effective July 1, 2023, mandatory from September 29, 2023, with local amendments in the KCBRC. Ceiling R-49, walls R-20 or R-13+5ci, mandatory 3 ACH50 blower door, duct leakage testing, REScheck accepted.

 

What energy code does St. Louis use?

The City of St. Louis has adopted the 2018 IECC with local amendments — a separate jurisdiction from St. Louis County, which has been working toward the 2015 IECC. Verify with the specific jurisdiction (city vs. county vs. individual municipality).

 

What climate zones does Missouri have?

Zone 4A (Mixed-Humid) covers most of the state including all major cities. Zone 5A (Cool-Humid) covers northern counties (Kirksville, Hannibal, Moberly areas), triggering stricter wall/floor insulation and no SHGC restriction.

 

Do rural Missouri counties require REScheck?

Most have adopted no energy code and don't require it — but some have quietly adopted codes without advertising it. Always verify with the local permit office. Voluntary IECC compliance is still recommended for energy performance and appraisal value.

 

What is HB 939?

Legislation that would cap local energy standards at the 2009 IRC/IECC statewide, rolling back Kansas City, Columbia, and St. Louis City to 2009-era standards. It cleared House committees in 2025 but didn't pass; a similar bill was refiled for 2026. Monitor the outcome for multi-year projects.

 

Are barndominiums required to comply in Missouri?

Only if the project is in a jurisdiction that has adopted an energy code. Required in Kansas City (2021 IECC) and St. Louis City (2018 IECC); not subject to energy code in rural counties without an adopted code.