South Carolina REScheck Requirements (2026)

Key facts:

• 2009 IECC — Current Enforceable Standard

• Climate Zones 2A & 3A

• Legislature Controls Energy Code

• Blower Door: 7 ACH50 or Visual Inspection

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South Carolina commonly requires REScheck for: new residential construction, residential additions/renovations, conditioned detached structures, barndominiums and ADUs. South Carolina's energy code is among the least restrictive in the nation — low insulation requirements, a lenient 7 ACH50 blower door threshold, and the option of visual inspection instead of testing.

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South Carolina jurisdictions require REScheck and energy compliance documentation under the South Carolina Energy Standard, S.C. Code Ann. § 6-10-30. The current energy code is the 2009 International Energy Conservation Code — adopted by the state legislature in 2012 (Act No. 143, effective January 1, 2013) and still the enforced standard in 2026.

Uniquely, South Carolina's energy code is set by the General Assembly, not the Building Codes Council — and the BCC explicitly does not adopt IRC Chapter 11. The state spans two IECC climate zones: Zone 3A (Upstate and Piedmont) and Zone 2A (Coastal Plain, Lowcountry, and most of the state).

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⚠ South Carolina's Energy Code Is Controlled by the State Legislature — Not the Building Codes Council: In most states, a building codes council adopts and updates the energy code through a regulatory process. In South Carolina, it's set by an act of the General Assembly (S.C. Code of Regulations 8-1230 explicitly excludes IRC Chapter 11). The last update was 2012 (Act No. 143), adopting the 2009 IECC effective January 1, 2013. A 2024 IBC commercial update is moving through adoption in 2025-2026, but this does NOT affect residential energy requirements — that requires a new act of the General Assembly.

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Statewide Code Structure

The South Carolina Energy Standard Act (S.C. Code Ann. §§ 6-10-10 through 6-10-50) governs residential energy requirements. Section 6-10-30 states verbatim: "The 2009 edition of the International Energy Conservation Code is adopted as the Energy Standard." Local jurisdictions may adopt more stringent codes but not less stringent ones.

• 2009 IECC — current residential energy standard, effective January 1, 2013

• Mandatory statewide for all new construction, renovations exceeding 50% of physical value, and additions

• SC Building Codes Council does NOT adopt IRC Chapter 11 — governed exclusively by the Energy Standard Act

• 2024 IECC commercial update in process — does NOT affect residential energy code

• SC is one of only a handful of states still on the 2009 IECC for residential construction as of 2026

 

Common Permit Requirements

• Energy compliance documentation — prescriptive checklist, REScheck (UA trade-off), or performance simulation

• Window and door schedule (U-factor and SHGC per NFRC)

• Insulation R-value specifications and installer certification

• Air leakage compliance — blower door test (7 ACH50) OR visual inspection per Table 402.4.2

• Duct leakage: post-construction max 8 CFM25/100 sq ft; rough-in 6 CFM25 (with air handler) or 4 CFM25 (without)

• Energy certificate posted at electrical panel — required for Certificate of Occupancy

• HVAC equipment sized per ACCA Manual J (Section 403)

 

South Carolina's Three Compliance Pathways

Pathway  ·  How It Works

• Prescriptive (§402.1.1):  Meet all R-values/U-factors by zone independently. No REScheck needed — prescriptive checklist submitted with permit.

• UA Trade-Off (§402.1.4) — REScheck:  Total UA ≤ reference design UA. REScheck accepted as the calc tool. SHGC still must be met separately, cannot be traded off.

• Simulated Performance (§405):  Whole-building energy simulation; proposed annual energy cost ≤ standard reference design. Mandatory requirements still apply.

 

Important: SHGC Cannot Be Traded Off in South Carolina. The 0.30 maximum SHGC in Zones 2A and 3A is mandatory and cannot be traded against other envelope improvements in the UA path — hot summers statewide make this a critical, and often underestimated, compliance detail.

 

South Carolina Climate Zones

Zone  ·  Coverage  ·  Classification  ·  Key Differences

• 3A:  Upstate/Piedmont — Greenville, Spartanburg, Anderson, Oconee, Pickens, Cherokee, York, Chester, Union, Laurens, Newberry, Fairfield, Lancaster, Chesterfield, Marlboro, Darlington   —   Warm-Humid   —   Window U-0.50 max (impact-rated: U-0.65); SHGC 0.30; higher heating loads

• 2A:  Midlands, Pee Dee, Lowcountry, Coast — Columbia, Charleston, Myrtle Beach, Florence, Beaufort, Hilton Head, Orangeburg, Sumter, Aiken, Georgetown, Horry   —   Hot-Humid   —   Window U-0.65 max (impact-rated: U-0.75); SHGC 0.30; more cooling-dominated

 

Zone 2A vs. Zone 3A Insulation Comparison (2009 IECC Table 402.1.1)

Requirement  ·  Zone 3A  ·  Zone 2A

• Ceilings:  R-30 min (R-38 where eave condition not met)   —   R-30 min

• Wood Frame Walls:  R-13 min (or R-13+5ci)   —   R-13 min

• Floor:  R-13 min   —   R-13 min

• Basement Walls:  R-5ci or R-13 cavity (verify warm-humid exception)   —   Not required in warm-humid locations

• Crawlspace Walls:  R-5ci or R-13 cavity   —   R-5ci or R-13 cavity (verify exception)

• Windows:  U-0.50 max (impact-rated: U-0.65)   —   U-0.65 max (impact-rated: U-0.75)

• SHGC:  0.30 max, mandatory   —   0.30 max, mandatory

 

⚠ Glazing Area Limitation Under Prescriptive Path: Total glazed area may not exceed 18% of conditioned floor area under §402.1.1. Projects exceeding this — coastal custom homes, lake houses, view-driven designs — must use the UA trade-off (REScheck) or simulated performance path instead.

 

Air Leakage and Duct Requirements

Air Leakage Compliance (§402.4) — Two Equally Valid Paths

• Option A — Blower Door Test: air leakage less than 7 ACH50 at 50 pascals, tested after rough-in with all envelope penetrations installed

• Option B — Visual Inspection: envelope tightness accepted when Table 402.4.2 items are field-verified (joints, windows, doors, plumbing, electrical, recessed lighting, attic hatches, HVAC boots, fireplace openings)

• 7 ACH50 is among the most lenient thresholds of any state that allows testing — same as Wisconsin

• Visual inspection is widely used in coastal markets where testing services may be less available

 

Duct Leakage Requirements (§403.2.2)

• Post-construction: max 8 CFM25 per 100 sq ft, tested with registers sealed

• Rough-in (with air handler): max 6 CFM25/100 sq ft; (without air handler): max 4 CFM25/100 sq ft

• Duct insulation: R-8 min for supply ducts in unconditioned attics; R-6 for other supply/return ducts in unconditioned spaces

• Energy certificate required in electrical panel for Certificate of Occupancy

 

Is REScheck Required in South Carolina?

• All new residential construction statewide

• Residential additions

• Renovations where alterations/repairs within 12 months exceed 50% of the building's physical value

• Replacement windows (must meet current zone's U-factor and SHGC)

• Conditioned barndominiums and ADUs

• Conditioned detached structures

 

Renovation threshold: South Carolina defines "renovation" as alterations/repairs costing more than 50% of the building's physical value within any 12-month period — a lower trigger than many states, which can catch remodeling contractors off guard.

 

South Carolina-Specific Notes

• REScheck accepted for UA trade-off documentation — most common path for custom homes exceeding prescriptive limits or the 18% glazing cap

• Enforcement consistency varies by jurisdiction — larger counties (Charleston, Greenville, Richland, Horry) actively enforce; some rural counties less so

• The 15 sq ft glazing exemption — up to 15 sq ft of glazed fenestration per dwelling unit is exempt from U-factor/SHGC requirements (prescriptive path only, §402.3.3)

• High-efficacy lighting: 50% of lamps in permanently installed luminaires must be high-efficacy

• Framing cavities may NOT be used as supply or return air ducts or plenums

 

Common REScheck Failure Reasons in South Carolina

Most Common Errors

• SHGC non-compliance — 0.30 max is mandatory and can't be traded off; coastal/lake properties with large window packages from other states (SHGC 0.32–0.40) frequently fail here

• Zone 2A/3A misidentification — applying Zone 3A's U-0.50 to a Zone 2A project (where U-0.65 is allowed)

• Prescriptive path with glazing over 18% — a very common correction on coastal and custom home projects; requires switching to UA trade-off (REScheck)

• Basement wall insulation included when not required in Zone 2A warm-humid locations — confirm the exception with the local official

• Impact-rated fenestration U-factor confusion — Zone 3A impact-rated is U-0.65 (not U-0.50); Zone 2A is U-0.75 (not U-0.65)

 

Mechanical & Field Issues

• Missing energy certificate at Certificate of Occupancy — must be posted in the electrical panel before CO

• Duct leakage failures — unsealed boots, improper mastic, unsealed air handler connections in the high-heat, high-humidity environment where duct tape fails over time

• Insulation installer certification missing — required for blown/sprayed insulation (type, manufacturer, R-value, density, coverage, bag count)

• Exterior insulation protective covering missing — basement/crawlspace exterior insulation needs a rigid, weather-resistant cover extending 6+ inches below grade

• HVAC sizing documentation — Manual J required per §403; oversized systems without it are a common correction, especially given the state's critical latent loads

 

Major Cities and Jurisdictions

Charleston & Lowcountry (Zone 2A)

Including Mount Pleasant, North Charleston, Summerville, Beaufort, Hilton Head. One of the most active coastal construction markets in the Southeast. Zone 2A's lenient U-0.65 window requirement is offset by the critical 0.30 SHGC requirement on west/south-facing elevations.

 

Columbia & Midlands (Zone 2A)

The state capital and South Carolina's highest-volume residential permit market. Spans Lexington, Kershaw, Calhoun, and Saluda counties. Richland and Lexington County offices are well-versed in the 2009 IECC.

 

Myrtle Beach & Grand Strand (Zone 2A)

One of the fastest-growing residential markets in the country. High glazing packages common in beach homes frequently push projects over the 18% limit, making REScheck the standard compliance tool here.

 

Greenville & Upstate (Zone 3A)

One of the fastest-growing manufacturing/residential markets in the Southeast (BMW, Michelin). Zone 3A's stricter U-0.50 window requirement is the main difference builders notice moving between Upstate and Midlands projects.

 

Rock Hill & York County (Zone 3A)

Charlotte metro growth has spilled into York County. Builders crossing the NC/SC line should note NC's stricter blower door threshold vs. SC's 7 ACH50.

 

Florence & Pee Dee (Zone 2A)

Steady residential activity requiring full 2009 IECC compliance. Local offices commonly accept the visual inspection path for air leakage.

 

Frequently Asked Questions

What energy code does South Carolina currently use?

The 2009 IECC, adopted by the General Assembly in 2012 (Act No. 143), effective January 1, 2013. SC Code § 6-10-30 states verbatim: "The 2009 edition of the International Energy Conservation Code is adopted as the Energy Standard." A 2024 IBC commercial update is in process, but the residential energy code requires a separate legislative act — none has passed as of 2026.

 

Why does South Carolina still use the 2009 IECC?

The energy code is controlled by the legislature, not the Building Codes Council. In 2009, Governor Sanford signed H.3550 removing the energy code from the normal BCC adoption process. Any update now requires a statutory amendment — a much slower process. Attempts to update to the 2015 or 2018 IECC have not passed.

 

Is blower door testing required in South Carolina?

Not mandatory — §402.4.2 offers two equally valid paths: a blower door test under 7 ACH50, or a visual inspection per Table 402.4.2. When tested, 7 ACH50 is the maximum — one of the most lenient thresholds of any state that permits testing.

 

What climate zones does South Carolina have?

Two: Zone 3A (Upstate/Piedmont — Greenville, Spartanburg, Anderson, York, Cherokee) and Zone 2A (most of the state — Columbia, Charleston, Myrtle Beach, Florence, Beaufort, all Lowcountry). Main practical difference: window U-factor (3A: U-0.50 max; 2A: U-0.65 max). Both share the 0.30 SHGC max.

 

What is the SHGC requirement?

0.30 maximum in both zones — mandatory, cannot be traded off in the UA path. The most common energy code failure on custom homes with large or west-facing window packages.

 

What is the glazing area limit on the prescriptive path?

18% of conditioned floor area (§402.1.1). Projects exceeding it must use the UA trade-off (REScheck) or simulated performance path — a significant limitation for coastal custom homes, lake properties, and view-driven designs.

 

Does South Carolina require REScheck for additions?

Yes, all additions must comply with the 2009 IECC. Renovations exceeding 50% of the building's physical value within 12 months must also comply. Replacement windows must meet current zone U-factor/SHGC. REScheck is accepted on the UA trade-off path.

 

Are barndominiums required to comply?

Yes, conditioned barndominiums must comply with the 2009 IECC regardless of construction type. Enforcement may vary by county. SHGC 0.30 and the 18% glazing limit are the most common compliance issues for barndominiums with large window/door openings.

 

Will South Carolina update its residential energy code soon?

No enacted legislation as of 2026. The BCC initiated a 2024 IBC adoption process for commercial construction in January 2025 (comment period through August 2025, expected effective date January or July 2026) — but the residential energy code requires a separate legislative bill. None has been enacted.