Mississippi REScheck Requirements (2026)

Key facts:

• No Statewide Energy Code — Home Rule

• Climate Zones 2A & 3A

• Biloxi: 2021 IECC

• REScheck Acceptance Varies by Jurisdiction

 

Mississippi has no mandatory statewide residential energy code. The state's 2014 building code law pushed cities and counties toward the IBC and IRC, but it let them opt out, and it never added an energy code requirement. Whether you need a REScheck depends on your city or county. Biloxi, for example, adopted the 2021 IECC in October 2021, while other jurisdictions run older editions of the IRC or have no energy code at all. The DOE's own state tracker lists REScheck as "applicable by county or jurisdiction," so the right move is to confirm with the local building department before ordering a report.

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Mississippi runs on home rule when it comes to energy codes. The Mississippi Development Authority's Energy & Natural Resources division tracks the issue at the state level, but it does not enforce a residential energy code. Each city or county decides whether to enforce one and which edition to use. A project three miles over a city line can have a completely different answer.

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How Mississippi's Building Code Structure Works

In 2014 Mississippi passed a law directing counties and municipalities to adopt one of the three most recent editions of the International Building Code or International Residential Code. Local governments had 120 days to opt out. The law was a response to Hurricane Katrina and focused on wind and flood safety. It did not add a statewide energy code, and Mississippi still has no statewide adoption date for the IECC.

 

⚠ Don't assume "Mississippi adopted the IRC" means a REScheck is required. The IRC includes an energy chapter (Chapter 11), but local governments can adopt the IRC and delete or skip that chapter. Some Mississippi jurisdictions enforce Chapter 11, some have removed it, and some have no energy requirement. The only reliable answer comes from the local building department.

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• No statewide residential energy code (DOE state tracker: "None Statewide")

• 2014 state law requires local adoption of a recent IBC/IRC edition, with a 120-day opt-out window

• Five coastal counties (Hancock, Harrison, Jackson, Pearl River, Stone) face stricter wind and flood enforcement rules, not an energy code

• The state references the 2021 IECC, but adoption is entirely up to each jurisdiction

 

What We Know About Specific Mississippi Jurisdictions

Jurisdiction  ·  What's Confirmed  ·  What To Do

• Biloxi:  2021 IECC, effective October 23, 2021   —   Run REScheck against the 2021 IECC (Zone 2A)

• Southaven (DeSoto County):  2018 ICC family of codes adopted; energy chapter edition not listed on the city's building page   —   Call the Southaven Building Department at 662-393-4639 to confirm the energy edition

• Jackson, Gulfport, Hattiesburg, Vicksburg, Oxford, and most other cities:  No single published energy code answer; adoption and edition vary and some have removed the energy chapter   —   Ask the permitting office whether they enforce an energy code and which edition

 

Mississippi Climate Zones

Mississippi splits into two IECC climate zones, both hot-humid. Only the five Gulf Coast counties sit in Zone 2A. Everything else, including the Jackson metro, the Delta, the Hills, and Hattiesburg, is Zone 3A.

Zone  ·  Counties  ·  Notes

• 2A:  Hancock, Harrison, Jackson, Pearl River, Stone   —   Gulf Coast. Includes Biloxi, Gulfport, Pascagoula, and Bay St. Louis.

• 3A:  All remaining counties, including Hinds, Rankin, Madison, DeSoto, Forrest, Lamar, Lafayette, Lee, Warren, and Washington   —   Jackson (city, in Hinds County), Hattiesburg, Southaven, Tupelo, Oxford, Meridian, Vicksburg, Greenville

 

Watch the name collision: Jackson County is on the Gulf Coast and sits in Zone 2A. The city of Jackson is in Hinds County and sits in Zone 3A. Picking the wrong one is an easy REScheck mistake.

 

Prescriptive Requirements (2021 IECC, Zones 2A and 3A)

These are the 2021 IECC prescriptive values, which apply wherever a Mississippi jurisdiction has adopted that edition, as Biloxi has. If your jurisdiction is on the 2018 edition, the ceiling R-values are one tier lower (R-38 instead of R-49 in both zones), so confirm the edition before you run the report.

Component  ·  Zone 2A (Gulf Coast)  ·  Zone 3A (Rest of State)

• Ceiling:  R-49   —   R-49

• Wood Frame Walls:  R-13   —   R-20, or R-13 + R-5ci, or R-15ci

• Floor:  R-13   —   R-19

• Slab-on-Grade:  Not required   —   R-10, 2 ft

• Basement / Crawl Space Walls:  Not required   —   R-5ci or R-13

• Fenestration (Windows):  U-0.40 max, SHGC 0.25 max   —   U-0.30 max, SHGC 0.25 max

 

Zone 2A ceilings can step down to R-30 with a qualifying cool roof (3-year aged solar reflectance of at least 0.55 and thermal emittance of at least 0.75). Biloxi's 2021 IECC adoption also requires one of five additional efficiency options under section R408, so that choice needs to be documented with the permit.

 

Air Leakage and Duct Testing

Where the 2021 IECC applies, blower door testing is mandatory. The base IECC limit is 5 ACH50 in Climate Zones 1 and 2 and 3 ACH50 in Zones 3 through 8. A published summary of Biloxi's adoption lists 3 ACH50 for its Zone 2 projects, so confirm Biloxi's exact threshold with the city before you test. Duct leakage limits under the 2021 IECC are 4 CFM25 per 100 sq ft of conditioned floor area at rough-in with the air handler installed, 3 CFM25 per 100 sq ft at rough-in without the air handler, and 4 CFM25 per 100 sq ft post-construction. Mechanical ventilation systems must also be tested per R403.6.3.

 

Is REScheck Accepted in Mississippi?

Where an energy code applies, yes. The 2021 IECC allows REScheck as a compliance path, and Mississippi's code references accept it. The DOE's state tracker lists REScheck availability for Mississippi as "applicable by county or jurisdiction," which is the honest summary: REScheck works wherever a jurisdiction enforces an IECC-based energy code, and no report is needed where a jurisdiction has no energy requirement. Ask the building department which situation you're in before you order.

 

Common Permit Requirements

• REScheck compliance report, where the jurisdiction enforces an energy code

• Manual J load calculations, where the jurisdiction asks for them with the mechanical permit

• Window schedule showing U-factor and SHGC

• Insulation R-value specs matching the applicable zone and code edition

• Blower door and duct leakage test results, where required

• R408 additional efficiency option documentation (Biloxi and any other 2021 IECC jurisdiction)

 

Common REScheck Failure Reasons in Mississippi

Most Common Errors

• Running the report against the wrong code edition, especially 2021 values in a jurisdiction still on 2018 (or the reverse)

• Mixing up Jackson County (Zone 2A) with the city of Jackson (Zone 3A)

• Window U-factor above the zone limit: 0.40 in Zone 2A, 0.30 in Zone 3A

• Ceiling insulation entered at R-38 when the 2021 IECC calls for R-49

 

Documentation Issues

• Submitting a REScheck to a jurisdiction that doesn't enforce an energy code, or skipping one in a jurisdiction that does

• Missing the R408 additional efficiency option selection on 2021 IECC projects

• Slab-edge insulation left off Zone 3A slab-on-grade projects

 

Major Cities and Jurisdictions in Mississippi

Biloxi

Zone 2A. Adopted the 2021 IECC effective October 23, 2021, including the R408 additional efficiency option requirement. This is the clearest 2021 IECC jurisdiction in the state.

 

Gulfport and the Gulf Coast

Zone 2A (Harrison, Hancock, Jackson, Pearl River, and Stone counties). Coastal jurisdictions face stricter wind and flood enforcement, but energy code adoption still varies city by city. Confirm locally.

 

Jackson and the Metro (Hinds, Rankin, Madison counties)

Zone 3A. Energy code enforcement varies between the city of Jackson and the surrounding suburbs. Confirm which edition applies with the specific permitting office.

 

Southaven and DeSoto County

Zone 3A. Southaven has the 2018 ICC family of codes adopted. Its building page doesn't list the energy chapter edition, so call the building department at 662-393-4639.

 

Hattiesburg

Zone 3A (Forrest and Lamar counties). Confirm the current energy code status with the city's building department.

 

Oxford, Tupelo, and North Mississippi

Zone 3A. Adoption and editions vary by city. Confirm locally.

 

Frequently Asked Questions About REScheck in Mississippi

Does Mississippi have a statewide energy code?

No. Mississippi has no mandatory statewide residential energy code. The state references the 2021 IECC, but each city and county decides whether to enforce an energy code and which edition to use.

 

Do I need a REScheck in Mississippi?

It depends on your jurisdiction. Where the local government enforces an IECC-based energy code, a REScheck is a standard way to show compliance. Where there is no local energy requirement, none is needed. Ask your building department which applies.

 

Is REScheck accepted in Mississippi?

Yes, wherever an IECC-based energy code is enforced. The DOE lists REScheck availability for Mississippi as applicable by county or jurisdiction.

 

What climate zones does Mississippi have?

Two: Zone 2A for the five Gulf Coast counties (Hancock, Harrison, Jackson, Pearl River, and Stone) and Zone 3A for the rest of the state.

 

What code does Biloxi use?

The 2021 IECC, effective October 23, 2021. Biloxi's adoption also requires one of five additional efficiency options under section R408.

 

What are the ceiling insulation requirements in Mississippi?

Under the 2021 IECC, R-49 in both Zone 2A and Zone 3A. Jurisdictions still on the 2018 IECC use R-38, so confirm the edition before you run a REScheck.

 

What if my county has no building department?

Check with your lender and the county board of supervisors. Some areas without their own building department route permits through a county or regional office, and a lender or insurer may still ask for energy compliance documentation.