Commercial insulation R-value targets in Arkansas are set by the building's climate zone and the adopted commercial energy code, applied to each assembly (roof, wall, floor). The mixed-humid climate makes seasonal swings and humidity management central, so continuous insulation and air-sealing matter as much as the nominal R-value.
R-value, and why the number is only the start
R-value is the assembly's resistance to conductive heat flow, and in Arkansas the commercial energy code fixes a minimum per component by climate zone. The catch is that a strong nominal number can be lost to thermal bridging through steel or studs and to air leakage, so continuous insulation and a real air barrier are specified with it, not instead of it. We install both as wall insulation and air sealing scopes.
The commercial energy code that applies in Arkansas
Arkansas enforces 2009 IECC and ASHRAE Standard 90.1-2007, with state amendments for commercial work, effective January 1, 2015. Local amendments can still apply, so the edition in force for a specific address is confirmed with the authority having jurisdiction.
| Item | Value |
|---|---|
| State | Arkansas |
| Adopted commercial energy code | 2009 IECC and ASHRAE Standard 90.1-2007, with state amendments |
| Effective date | January 1, 2015 |
| Climate zone | Assigned by county in the adopted code’s climate zone tables |
| Source | U.S. Department of Energy, Building Energy Codes Program |
| Last verified | August 2026 |
Which table governs in Arkansas, and how to read it
A commercial project in Arkansas is judged against the envelope tables in 2009 IECC and ASHRAE Standard 90.1-2007, with state amendments. In the IECC commercial provisions those are the insulation R-value table and the matching assembly U-factor table in Section C402. Two things decide which column you read: the county's climate zone, listed in the next section, and whether the space is a Group R occupancy or falls under the "all other" column.
R-value method or U-factor method
The code offers two prescriptive routes and they are not interchangeable on a drawing. The R-value method lists a minimum insulation R-value per assembly, counting only the insulation, which makes it simple to specify and inspect. The U-factor method sets a maximum for the assembly as a whole, including framing, sheathing and air films, which is how a design team earns credit for continuous insulation that interrupts thermal bridging. An assembly that fails the R-value line can still comply on U-factor, and that decision belongs to the design professional, not the installer.
2021 IECC reference values for Arkansas climate zones
Arkansas adopted 2009 IECC and ASHRAE Standard 90.1-2007, with state amendments. Its tables govern and are not reproduced here. The 2021 IECC values below are shown for reference only, for the climate zones our Arkansas markets fall in on the 2021 county map; the adopted edition's values, and its county map, can differ.
2021 IECC, Tables C402.1.3 and C402.1.4, "All other" (nonresidential) column, shown for reference. R-value method, with the matching assembly U-factor (or F-factor for slabs) in parentheses.
| Assembly | Zone 3 | Zone 4 (except Marine) |
|---|---|---|
| Roof, insulation entirely above deck | R-25ci (U-0.039) | R-30ci (U-0.032) |
| Roof, metal building | R-19 + R-11 LS (U-0.035) | R-19 + R-11 LS (U-0.035) |
| Roof, attic and other | R-38 (U-0.027) | R-49 (U-0.021) |
| Wall above grade, metal building | R-13 + R-6.5ci (U-0.079) | R-13 + R-13ci (U-0.052) |
| Wall above grade, metal framed (steel stud) | R-13 + R-7.5ci (U-0.064) | R-13 + R-7.5ci (U-0.064) |
| Wall above grade, mass (concrete, CMU, tilt-up) | R-7.6ci (U-0.123) | R-9.5ci (U-0.104) |
| Floor over unconditioned space, joist or framing | R-30 (U-0.033) | R-30 (U-0.033) |
| Slab-on-grade, unheated | NR (F-0.73) | R-15 for 24 in. below (F-0.52) |
| Slab-on-grade, heated | R-10 for 24 in. below + R-5 full slab (F-0.66) | R-15 for 24 in. below + R-5 full slab (F-0.62) |
ci = continuous insulation; LS = liner system; NR = no requirement. Metal building roofs on the R-value method need a thermal spacer block. Group R occupancies use a different column. Source: International Code Council, 2021 IECC, Tables C402.1.3 and C402.1.4, read October 25, 2026.
Confirm the code for your project. This is general planning guidance, not a code determination. The building department for the project address confirms the edition, the climate zone, and any local amendments.
For a specific building, the written estimate names the system and thickness that meet the target.
Climate zones for Arkansas markets
Climate zone is assigned by county, so the envelope requirements for a building in one Arkansas market can differ from another. The table lists the county zone for each market this site covers, on the 2021 IECC map and on the earlier 2009 to 2018 map where it was verified.
Arkansas' adopted commercial code predates the 2021 map, so the earlier-map zone governs compliance where the two differ. Source: International Code Council, 2021 IECC Table C301.1. Reviewed September 2026.
| Market | County or jurisdiction | 2021 IECC zone | Earlier map |
|---|---|---|---|
| Bentonville | Benton County | 4A (mixed, humid) | 4A |
| Fayetteville | Washington County | 4A (mixed, humid) | 4A |
| Little Rock | Pulaski County | 3A (warm, humid) | 3A |
| Rogers | Benton County | 4A (mixed, humid) | 4A |
| Springdale | Washington County | 4A (mixed, humid) | 4A |
| West Memphis | Crittenden County | 3A (warm, humid) | 3A |
Heating and cooling load across Arkansas markets
Climate zone sets the code minimum, but degree days describe what the envelope works against in a normal year. The figures below are NOAA 1991 to 2020 annual normals, base 65°F, from the nearest first-order station to each market.
At the Memphis International Airport station (West Memphis), heating outweighs cooling. Bentonville runs about 1,225 more heating degree days a year than West Memphis. Source: NOAA NCEI U.S. Climate Normals.
| Market | Heating degree days | Cooling degree days | NOAA station |
|---|---|---|---|
| Bentonville | 4,190 | 1,308 | Fayetteville Drake Field |
| Fayetteville | 4,190 | 1,308 | Fayetteville Drake Field |
| Little Rock | 3,053 | 2,206 | Little Rock Airport Adams Field |
| Rogers | 4,190 | 1,308 | Fayetteville Drake Field |
| Springdale | 4,190 | 1,308 | Fayetteville Drake Field |
| West Memphis | 2,965 | 2,258 | Memphis International Airport |
Prescriptive path or performance path
Compliance in Arkansas runs down one of two tracks. The prescriptive route fixes a minimum per assembly and is the simpler path to specify and inspect. The performance route models the whole envelope against an energy target and permits trade-offs between assemblies, which suits buildings that will never fit the table cleanly. The systems that suit each assembly are compared on the commercial insulation systems comparison page.
Frequently asked questions
What is continuous insulation and why does Arkansas code call for it?+
Continuous insulation runs unbroken across framing so heat cannot bridge through steel or studs. Commercial codes lean on it because a cavity-only assembly can miss its effective R-value once bridging is counted.
Which Arkansas code edition applies to my building?+
Arkansas enforces one edition statewide: 2009 IECC and ASHRAE Standard 90.1-2007, with state amendments, effective January 1, 2015.
How is the R-value for my project set?+
By the assembly, the occupancy, and the code path. The written estimate names the system and thickness that meet the target.
What R-value do commercial buildings need in Arkansas?+
It depends on the climate zone and the adopted commercial energy code, applied per assembly (roof, wall, floor). Verify the adopted edition for your jurisdiction.
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