Oklahoma REScheck Requirements (2026)

Key facts:

• 2018 IRC with OK Amendments — Sept. 14, 2022

• Zones 3A (Most) & 4A (Panhandle)

• Blower Door: 5 ACH50 OR Visual Inspection

• Home Rule — Local Can Be Stricter

 

Oklahoma commonly requires REScheck for new residential construction, residential additions and alterations, conditioned detached structures, and barndominiums and ADUs. REScheck is accepted statewide for the UA trade-off compliance path. Oklahoma significantly amended the base 2018 IRC — Zone 3A ceiling insulation is only R-30 (vs. R-38 base), walls R-13 cavity (vs. R-20 or R-13+5), windows U-0.38 (vs. U-0.32), and blower door 5 ACH50 with a visual inspection alternative. Notably, Oklahoma moved the energy certificate requirement to a non-mandatory appendix — energy certificates are not required by state minimum code.

 

Oklahoma jurisdictions require REScheck and energy compliance documentation for residential permit applications under the 2018 International Residential Code with Oklahoma amendments, adopted statewide by the Oklahoma Uniform Building Code Commission (OUBCC), effective September 14, 2022. Oklahoma's energy requirements are in Chapter 11 (N1102 series) of the 2018 IRC with significant state-specific amendments that reduce requirements compared to the base 2018 IRC — including relaxed ceiling insulation, wall insulation, window U-factor, SHGC, and blower door requirements for Climate Zone 3. Oklahoma spans two IECC climate zones: Zone 3A (Mixed-Humid, covering most of the state) and Zone 4A (Cold, covering Panhandle and northwestern counties). Oklahoma is a home rule state — local jurisdictions may adopt more stringent requirements but not less stringent.

 

Current Energy Code in Oklahoma

Statewide Code Structure

Oklahoma's residential energy code is Chapter 11 of the 2018 International Residential Code (IRC), as adopted and amended by the Oklahoma Uniform Building Code Commission (OUBCC) under Oklahoma Administrative Code Title 748, Chapter 20, Subchapter 6. The 2018 IRC is the statewide minimum code for all one- and two-family dwellings and townhouses, effective September 14, 2022. Oklahoma is a home rule state — all jurisdictions may adopt these minimum codes for their area and may also adopt codes that are more restrictive but not less restrictive.

• 2018 IRC with Oklahoma amendments — statewide minimum effective September 14, 2022

• Energy provisions in Chapter 11 (N1102 series) with significant Oklahoma-specific amendments

• Administered by OUBCC; enforced by local building departments

• Home rule state — local jurisdictions may be more stringent but not less

• No local jurisdiction has adopted a code more stringent than the state minimum as of 2026

• OUBCC is currently reviewing the 2021 and 2024 IECC for future commercial code update; residential update timeline not confirmed

 

Common Permit Requirements

• REScheck compliance report (prescriptive or UA trade-off path) — widely accepted at Oklahoma permit offices

• Manual J HVAC load calculations (equipment sizing requirement per N1103.7)

• Window and door schedule (U-0.38 max Zone 3A; SHGC 0.30 max Zone 3A)

• Insulation R-value specifications and documentation

• Air leakage compliance — blower door test (5 ACH50 Zone 3A) OR visual inspection per Table N1102.4.1.1

• Duct leakage test results (when ducts outside thermal envelope)

• Note: Energy certificate (N1101.14) moved to non-mandatory Appendix W — NOT required statewide; verify with local jurisdiction

 

Oklahoma Significantly Relaxed the Base 2018 IRC for Zone 3A: Oklahoma's OUBCC amendments to the 2018 IRC Chapter 11 table for Climate Zone 3 are among the most significant weakening amendments of any state in the country. Builders familiar with the base 2018 IRC should not assume the standard national values apply in Oklahoma. Every Zone 3A value — ceiling, wall, window U-factor, SHGC, and blower door threshold — has been relaxed from the base code. The result is one of the most lenient residential energy codes for any mixed-humid climate zone in the United States.

 

Oklahoma's Three Compliance Pathways

Prescriptive Path (Table N1102.1.2)

• Meet all R-values and U-factors from Oklahoma's amended Table N1102.1.2 by climate zone

• Zone 3A: Ceiling R-30, wall R-13, floor R-13, basement R-5/13, window U-0.38, SHGC 0.30

• Zone 4A (Panhandle): Standard base 2018 IRC values — ceiling R-38, wall R-20 or R-13+5ci, window U-0.32, SHGC 0.40

• No REScheck required for straightforward prescriptive projects

• Most common path for standard Oklahoma new construction

 

UA Trade-Off / REScheck Path (N1102.1.5)

• Total building UA ≤ reference design UA

• REScheck accepted as documentation tool

• Allows component trade-offs within the envelope

• SHGC requirements must still be met — cannot be traded off

• Useful for custom homes and projects with architectural constraints

• Widely accepted at Oklahoma City, Tulsa, and other major jurisdiction permit offices

 

ERI / Performance Path (N1105 / N1106)

• Energy Rating Index maximum: 62 for Zone 3 (Oklahoma amendment — raised from base IECC value)

• Energy Rating Index maximum: 55 for Zone 4 (Panhandle)

• HERS Rater required for ERI path certification

• All mandatory requirements still apply regardless of path

• Simulated Performance Alternative (N1105) also available using approved software

 

Oklahoma Climate Zones and Insulation Requirements

Oklahoma spans two IECC climate zones. Zone 3A (Mixed-Humid) covers the vast majority of the state — all major population centers including Oklahoma City, Tulsa, Norman, Lawton, Edmond, Broken Arrow, Stillwater, and Muskogee. Zone 4A (Cold) covers the Oklahoma Panhandle (Cimarron, Texas, and Beaver counties) and some northwestern Oklahoma counties. The zone distinction matters significantly — Oklahoma's OUBCC amendments relaxed Zone 3 values but left Zone 4 at base 2018 IRC levels, creating meaningfully different requirements for Panhandle construction.

Assembly  ·  Zone 3A (Oklahoma amended)  ·  Zone 4A (Base 2018 IRC)  ·  Base 2018 IRC Zone 3 (for comparison)

• Ceiling / Attic:  R-30   —   R-38 (R-30 eave exception)   —   R-38 — Oklahoma reduced to R-30

• Wood Frame Walls:  R-13 cavity only   —   R-20 cavity OR R-13+5ci   —   R-20 or R-13+5ci — Oklahoma reduced to R-13

• Floor:  R-13   —   R-19   —   R-13 — same as base IECC Zone 3

• Basement Walls:  R-5ci or R-13 cavity   —   R-10/13   —   R-5ci or R-13 — same as base

• Slab Edge:  Not required (Zone 3A)   —   R-10 at 2 ft depth   —   Not required Zone 3

• Windows:  U-0.38 maximum   —   U-0.32 maximum   —   U-0.32 — Oklahoma relaxed to U-0.38

• SHGC:  0.30 maximum   —   0.40 maximum   —   0.25 — Oklahoma relaxed to 0.30

• Blower Door:  5 ACH50 OR visual inspection   —   3 ACH50   —   3 ACH50 — Oklahoma relaxed to 5 ACH50 with visual inspection option

 

Zone 4A (Oklahoma Panhandle) Uses Standard 2018 IRC Values: Oklahoma's OUBCC amendments relaxed Zone 3 requirements but did not amend Zone 4. Builders working in the Oklahoma Panhandle counties (Cimarron, Texas, and Beaver counties) and some northwestern counties must use the base 2018 IRC Zone 4 values: R-38 ceilings, R-20 or R-13+5ci walls, U-0.32 windows, SHGC 0.40, and 3 ACH50 blower door — significantly stricter than Zone 3A. Always verify the specific county climate zone before completing documentation for Panhandle projects.

 

Air Leakage and Duct Requirements

Air Leakage Compliance (Zone 3A)

• Oklahoma amended the base 2018 IRC blower door threshold from 3 ACH50 to 5 ACH50 for Climate Zone 3

• Visual inspection per Table N1102.4.1.1 is a fully valid alternative to blower door testing

• Both paths are equally valid — builders may choose either

• When blower door testing is performed: testing per RESNET/ICC 380 or ASTM E779/E1827; written report required

• Visual inspection covers all major envelope penetration types: joints, windows, doors, plumbing, electrical, recessed lighting, attic hatches, HVAC boots, fireplace openings

• 5 ACH50 is a lenient threshold — most Oklahoma homes built to code pass without aggressive air sealing

• Mechanical ventilation required when home tests below 5 ACH50 (the trigger point under 2018 IRC N1103.5 for Zone 3A)

 

Duct Leakage Requirements

• Duct leakage testing required when any portion of the distribution system is outside the building thermal envelope

• Ducts entirely within conditioned space do not require testing — duct testing exemption applies

• Post-construction total leakage: maximum 4 CFM25 per 100 sq ft of conditioned floor area

• Rough-in (with air handler): maximum 4 CFM25 per 100 sq ft

• Rough-in (without air handler): maximum 3 CFM25 per 100 sq ft

• Duct insulation: R-8 for ducts in attics; R-6 for other supply and return ducts outside conditioned space

• Framing cavities (stud bays, joist spaces) may NOT be used as supply ducts or plenums

 

Oklahoma-Specific Code Notes

Energy Certificate — NOT Required Statewide

One of Oklahoma's most distinctive code features is the treatment of the energy certificate requirement. The base 2018 IRC Section N1101.14 (R401.3) requires a mandatory energy certificate to be permanently posted at the electrical panel. Oklahoma's OUBCC moved this section to the newly created Appendix W ("Energy Efficiency") and explicitly designated it as not adopted as part of the statewide minimum code.

This means the energy certificate is NOT required at the state minimum code level for Oklahoma residential construction. However, local jurisdictions that specifically reference Appendix W in their local adopting ordinance may still require it. Always verify with the local building department. This is one of the most frequently misunderstood aspects of Oklahoma's energy code among builders who work in multiple states.

 

Home Rule and Local Authority

• Oklahoma is a home rule state — all jurisdictions have the ability to adopt more stringent codes than the OUBCC statewide minimum

• No Oklahoma jurisdiction has currently adopted energy requirements more stringent than the statewide base code as of 2026

• Local jurisdictions enforce codes through their own building departments — contact the local AHJ (Authority Having Jurisdiction) to confirm current requirements

• Oklahoma City and Tulsa building departments are the highest-volume residential permit offices; both accept REScheck for energy compliance documentation

• State agencies and political subdivisions (schools, government buildings) may adopt construction codes that exceed the statewide energy code

• OUBCC is currently reviewing the 2021 and 2024 IECC for potential future commercial code updates; residential energy code update timeline is not yet established

 

Is REScheck Required in Oklahoma?

Projects Requiring Documentation

• New single-family homes

• Duplexes and townhomes

• Conditioned residential additions and alterations

• Finished basement conversions

• Garage conversions to conditioned space

• Conditioned sunrooms and bonus rooms

• Conditioned barndominiums

• Accessory dwelling units (ADUs)

 

Additions: Per N1103.1 of the 2018 IRC, additions must comply with the code as they apply to new construction without requiring the unaltered portions to comply. REScheck accepted for addition UA trade-off documentation.

 

Oklahoma-Specific Notes

• REScheck widely accepted at Oklahoma City, Tulsa, Norman, Edmond, and other major jurisdiction permit offices for the UA trade-off compliance path

• The prescriptive path does not require REScheck — a completed energy compliance checklist is acceptable

• Energy certificate (N1101.14) is NOT required at the state minimum code level — moved to non-mandatory Appendix W; verify with local jurisdiction

• Blower door testing is NOT mandatory — visual inspection per Table N1102.4.1.1 is equally valid

• Duct leakage testing is NOT required when ducts are entirely within conditioned space

• HVAC equipment must be sized per ACCA Manual J or equivalent method (N1103.7)

• High-efficacy lighting: all permanently installed lighting must be high-efficacy per N1104.1

 

Common REScheck Failure Reasons in Oklahoma

Most Common Errors

• Using base 2018 IRC values instead of Oklahoma's amended values — entering R-38 ceiling instead of R-30, R-20 or R-13+5ci walls instead of R-13, or U-0.32 windows instead of U-0.38 for Zone 3A projects. Oklahoma's amendments are significant reductions from the base code and builders using national references will over-specify, which isn't a code failure — but it does cause confusion if the REScheck output doesn't match permit office expectations

• SHGC non-compliance — the 0.30 maximum SHGC for Zone 3A windows is sometimes missed or entered at the higher 0.25 (more stringent than required) or at a higher value from other states; 0.30 is the Zone 3A OUBCC-amended value

• Zone 3A vs. Zone 4A confusion for Panhandle projects — applying Zone 3A's relaxed values to a Cimarron, Texas, or Beaver County project which is Zone 4A and requires R-38 ceiling, R-20/R-13+5ci walls, and 3 ACH50 blower door

• Floor insulation omitted — R-13 minimum for floors above unconditioned space; commonly omitted from documentation on slab-on-grade projects where no raised floor exists (no issue) but missed when raised floors are present

• Missing slab-edge insulation for Zone 4A projects — R-10 at 2 ft required in Zone 4A; frequently omitted for Panhandle projects by builders unfamiliar with Zone 4 requirements

 

Mechanical & Field Issues

• Blower door failures — 5 ACH50 is lenient but homes with rim joist bypasses, top-plate penetrations, recessed lighting, and poorly sealed HVAC boot connections can still exceed it; Oklahoma's hot summers mean envelope failures create cooling energy losses and comfort problems even at 5 ACH50

• Duct leakage failures in attic systems — unconditioned attic duct systems with unsealed boots and air handler cabinet leaks regularly fail the 4 CFM25/100 sq ft standard; Oklahoma's extreme summer attic temperatures (150°F+) make proper duct sealing critical for both compliance and long-term energy performance

• Framing cavity used as supply duct — prohibited under N1103.3; occasionally seen in older construction practice; requires plan revision

• Mechanical ventilation triggered — when blower door result falls below 5 ACH50, whole-house mechanical ventilation is required per N1103.5; some builders achieve tight results without planning for ventilation

• High-efficacy lighting not specified — all permanently installed luminaires must use high-efficacy lamps per N1104.1; occasionally omitted from documentation review

 

Major Cities and Jurisdictions in Oklahoma

Oklahoma City & Metro (Zone 3A)

Oklahoma City and the greater OKC metro — including Edmond, Norman, Moore, Yukon, Mustang, Midwest City, Del City, and Bethany — are in Climate Zone 3A. As the state capital and largest city, Oklahoma City has one of the state's highest-volume residential permit markets. The Oklahoma City Development Services Department enforces the 2018 IRC with OUBCC amendments. REScheck is accepted for energy compliance documentation. The Zone 3A amended values apply: R-30 ceiling, R-13 walls, U-0.38 windows, SHGC 0.30, 5 ACH50 or visual inspection.

 

Tulsa Metro (Zone 3A)

Tulsa and the northeastern Oklahoma metro — including Broken Arrow, Owasso, Jenks, Bixby, Sand Springs, and Sapulpa — are in Climate Zone 3A. Tulsa is Oklahoma's second-largest city and an active residential construction market. Tulsa Development Services enforces the 2018 IRC with OUBCC amendments. The same Zone 3A relaxed requirements apply as in Oklahoma City. REScheck is accepted for UA trade-off compliance documentation.

 

Lawton, Stillwater & Other Major Cities (Zone 3A)

Lawton (Comanche County), Stillwater (Payne County), Muskogee, Shawnee, Enid, Bartlesville, and all other major Oklahoma cities except the Panhandle communities are in Climate Zone 3A. The same OUBCC-amended Zone 3A requirements apply statewide in this zone. Local building departments vary in enforcement capacity; always verify current permit requirements with the local AHJ before submitting documentation.

 

Oklahoma Panhandle (Zone 4A)

The Oklahoma Panhandle — Cimarron County (Boise City), Texas County (Guymon), and Beaver County — is in Climate Zone 4A. Zone 4A requires base 2018 IRC values: R-38 ceilings, R-20 cavity or R-13+5ci walls, U-0.32 windows, SHGC 0.40, and 3 ACH50 blower door. The Panhandle's cold, dry climate (design temperatures well below 0°F in Boise City) makes Zone 4A's stricter requirements well-suited to local conditions. Builders working across the Zone 3A/4A boundary — particularly in northwestern Oklahoma counties — must verify the correct zone assignment for each project county.

 

Frequently Asked Questions About REScheck in Oklahoma

What energy code does Oklahoma currently use?

Oklahoma's current residential energy code is Chapter 11 of the 2018 International Residential Code (IRC) with Oklahoma-specific amendments, as adopted by the Oklahoma Uniform Building Code Commission (OUBCC) under Administrative Code Title 748, effective September 14, 2022. Oklahoma's OUBCC significantly relaxed the base 2018 IRC energy requirements for Climate Zone 3 (which covers most of the state): ceiling insulation reduced from R-38 to R-30, wall insulation reduced from R-20 or R-13+5ci to R-13, window U-factor relaxed from U-0.32 to U-0.38, SHGC relaxed from 0.25 to 0.30, and blower door raised from 3 ACH50 to 5 ACH50 with visual inspection as a valid alternative. The energy certificate requirement was moved to a non-mandatory appendix.

 

What climate zones does Oklahoma have?

Oklahoma spans two IECC climate zones. Zone 3A (Mixed-Humid) covers the vast majority of the state — all major population centers including Oklahoma City, Tulsa, Norman, Lawton, Enid, Stillwater, and Muskogee. Zone 4A (Cold) covers the Oklahoma Panhandle (Cimarron, Texas, and Beaver counties) and some northwestern Oklahoma counties. Zone 3A uses Oklahoma's relaxed amended values; Zone 4A uses base 2018 IRC values which are significantly stricter.

 

Is blower door testing required in Oklahoma?

Blower door testing is not mandatory in Oklahoma for Zone 3A projects. The OUBCC amended the base 2018 IRC to raise the Zone 3 blower door threshold from 3 ACH50 to 5 ACH50 and to permit visual inspection per Table N1102.4.1.1 as a fully valid alternative. Both paths are equally valid — builders may choose either. In Zone 4A (Panhandle), the base 2018 IRC applies with a 3 ACH50 threshold and mandatory testing (no visual inspection alternative).

 

Is REScheck required in Oklahoma?

REScheck is accepted but not the only option in Oklahoma. The prescriptive path (meeting all R-values from Oklahoma's amended Table N1102.1.2 independently) does not require REScheck — a prescriptive checklist is sufficient. REScheck is used for the UA trade-off compliance path, where it documents that the total building thermal envelope UA is less than or equal to the reference design UA. REScheck is widely accepted at Oklahoma City, Tulsa, and all major Oklahoma permit offices for new residential construction and additions.

 

Why is Oklahoma's energy code so different from the base 2018 IRC?

Oklahoma's OUBCC made significant amendments to the base 2018 IRC energy requirements for Climate Zone 3. Oklahoma reduced ceiling insulation requirements from R-38 to R-30, wall insulation from R-20 or R-13+5ci to R-13 cavity only, window U-factor from U-0.32 to U-0.38, SHGC from 0.25 to 0.30, and blower door from 3 ACH50 to 5 ACH50 with visual inspection as an alternative. These amendments were justified on the basis of Oklahoma's hot climate (Zone 3A summers) and to keep construction costs manageable. The result is one of the most lenient residential energy codes among states with a mandatory statewide code.

 

Is the energy certificate required in Oklahoma?

At the statewide minimum code level, no. Oklahoma's OUBCC moved the energy certificate requirement (Section N1101.14, R401.3) from the mandatory portion of Chapter 11 to a newly created non-mandatory Appendix W. This means the energy certificate — typically posted at the electrical panel — is NOT required by state minimum code. However, local jurisdictions that specifically adopt Appendix W in their local ordinance may still require it. Always verify with the local building department whether the energy certificate is required for your project jurisdiction.

 

Does Oklahoma require REScheck for additions?

Yes. The 2018 IRC as adopted by Oklahoma requires additions to comply with the energy requirements of the code as they apply to new construction, without requiring the unaltered portions of the existing building to comply. REScheck is accepted for the UA trade-off compliance path for additions. The blower door or visual inspection requirements and duct leakage testing (when applicable) also apply to addition construction.

 

Are barndominiums required to comply with the Oklahoma energy code?

Yes. Conditioned barndominiums in Oklahoma must comply with the 2018 IRC with OUBCC amendments, as the statewide minimum code applies to all one- and two-family dwellings regardless of construction type. For Zone 3A projects — which covers the vast majority of Oklahoma — this means R-30 ceiling, R-13 walls, U-0.38 windows, SHGC 0.30, and 5 ACH50 or visual inspection for air leakage. Verify current permit requirements with the local building department. Unconditioned agricultural structures are typically exempt.