How much insulation the law actually asks for on your street, who pays you to put it in, and the two things in an old Charleston attic that stop a job before it starts. Of the 36 jurisdictions on this site, 36 publish an energy code edition and 36 a required attic R-value. Every claim below names its source.
Section 6-10-30 of the Energy Standard Act adopts the 2009 edition of the International Energy Conservation Code as the Energy Standard, a change from the 2006 edition that took effect on January 1, 2013. The Building Codes Council's notice for the 2024 codes, which local governments begin enforcing on January 1, 2027, says the 2009 edition remains the energy standard because the statute adopted it, and that it is mandatory in every jurisdiction in the state.
The Act applies the standard to new buildings, additions and renovations, and it defines a renovation as alterations or repairs costing more than half of the building's value within any twelve-month period (S.C. Code 6-10-20 and 6-10-30). An attic top-up on a house you already own is none of those, so the state figures are the benchmark for that work rather than a rule it is held to; a permit desk that reviews it, as the City of Charleston does with its energy compliance form, looks for the same R-30 ceiling.
The Building Codes Council adopts the newest residential code on its own cycle, but the energy standard is set by the Act itself, so a new residential code does not move the insulation figures. The Council does not adopt the residential code's own energy chapter.
Every South Carolina jurisdiction on this site answers to the South Carolina Energy Standard (the 2009 IECC, adopted by statute): R-30 for the attic and R-13 for walls in new work, climate zone 3.
Code minimums are written for new construction and they are the least you may legally do. The Department of Energy publishes a separate recommendation for what actually pays for itself in this climate zone, and it is higher.
| Where | DOE recommendation, zone 3 | Note |
|---|---|---|
| Attic, uninsulated | R49 | The depth that reaches it depends on the material, which is why we mark it on a ruler rather than quote inches |
| Attic with 3–4 inches already there | R38 | The common case in an older house here: something is up there, just not enough of it |
| Floor over a crawl space | R19 | Only if the crawl space is vented and stays that way |
| Wood frame wall, uninsulated | Add R5 insulative sheathing under new siding | New construction figures; a dense-pack retrofit is judged on what fits the cavity |
| Wall already insulated, 2x4 | None listed for zone 3 | Continuous exterior board, which is a siding job, not an insulation-only one |
ENERGY STAR's table is based on the 2021 International Energy Conservation Code's Table R402.1.3. All three counties on this site — Charleston, Berkeley and Dorchester — are in IECC climate zone 3A, hot-humid, below the line the code draws for warm-humid locations.
The code sets the number. These are the layers that deliver it, numbered from the top.
| Figure | Number | What it drives |
|---|---|---|
| Climate zone | Zone 3A, hot-humid | Every R-value in the state table, in all three counties |
| Heating degree days | 1,844 | How hard the furnace works. Base 65°F, 1991–2020 normals at Charleston International Airport |
| Cooling degree days | 2,434 | Why an under-insulated attic costs you in July as well as January |
| Nights at or below freezing | 22.4 | How often the cold reaches the attic at all |
| Days that never rise above freezing | 0.1 | Close to none: a day that stays below freezing is rare here |
NOAA publishes both pairs of figures, and they are printed here as published. The degree days show that a house here spends far more of the year being cooled than heated, which is why the attic, and anything running through it, matters most; the freezing figures show how seldom the cold reaches it at all.
Which program applies depends on the utility named on your electric bill, and in these three counties that can change from one street to the next: Berkeley Electric Cooperative's territory runs through parts of all three counties alongside Dominion Energy South Carolina, Santee Cooper serves retail customers in Berkeley County, and Edisto Electric and Coastal Electric serve parts of Dorchester County. None of them publishes a town-by-town list, so the bill is the answer.
Dominion's free Home Energy Check-up is an in-home visit of about one to two hours for residential electric customers, owners and renters alike, with a look at the attic insulation, the ductwork and the weather stripping and a few free items installed. Nobody gets into Home Energy Check-up Plus without it. Under a limited-time offer, Check-up Plus pays 90% of qualifying attic insulation, air sealing and duct sealing, up to $2,880, for work completed by March 31, 2027; outside that offer it pays 75% of eligible improvements, up to $2,400, on a project cost capped at $3,200. Customers who completed Check-up Plus work before June 1, 2026 are not eligible for the 90% offer.
Berkeley Electric pays no insulation rebate; it lends. HomeAdvantage is a 5% loan of up to $20,000 for energy improvements to an existing home, insulation and air sealing among them, repaid on the electric bill. A certified auditor visits first and lists the work, which has to pay for itself in roughly six years to be recommended; an approved contractor does it, the cooperative inspects it, and a lien is recorded on the property. Members must have been with the cooperative for twelve months. Energy Advance loans, made through Farmers & Merchants Bank, run from $1,000 to $50,000 at 9.00% to 10.50% depending on the term, again with an approved contractor and a final inspection. Members can also ask for a free energy audit, and low- and moderate-income households in Berkeley County can apply for the cooperative's Hope Repair grant.
Santee Cooper's retail customers in Berkeley County get no insulation or air sealing money from its 2026 program. It pays $500 toward replacing more than half of a home's ductwork through one of its Trade Allies, with leakage tests before and after, until its program year ends on November 30, 2026; its 5% loans cover heat pumps and ductwork, not insulation. Its free Home Energy House Call is an hour-long visit from an energy advisor.
Coastal Electric Cooperative, which serves part of Dorchester County, offers an Energy Advance loan capped at $10,000, with terms up to five years and payments on the power bill, for insulation, caulking and weather stripping among other upgrades, with a credit check and a lien; it also offers free home energy check-ups. Edisto Electric Cooperative lists no insulation program; it publishes a do-it-yourself energy audit booklet.
South Carolina's federally funded Home Energy Rebates are not open yet: the state's own rebate page says they are expected to launch in 2026 and that a list of approved contractors will be posted when they do. Until then there is nothing to apply for, and nobody can put them in a price.
If the household income qualifies, the work can be free rather than discounted, through the South Carolina Weatherization Assistance Program. It is run county by county:
That is a different queue from a paid job, and worth checking before anyone quotes you.
EPA describes vermiculite insulation as "a pebble-like, pour-in product" that is "usually gray-brown or silver-gold in color." It appears as shiny, expanded flakes poured between attic joists or into wall cavities, not as batts or blown fiber. EPA states the Libby, Montana mine "supplied over 70 percent of all vermiculite sold in the United States from 1919 to 1990" and that "the vermiculite from Libby was contaminated with asbestos."
The federal asbestos rule, the Asbestos NESHAP, excludes residential buildings of four or fewer dwelling units. South Carolina runs its own asbestos program through the Department of Environmental Services, whose renovation and demolition page puts the facility owner and the contractor in charge of compliance and sends questions to its Asbestos Section, at (803) 898-4289. Ask that office what applies to your house before anyone touches the material. We do not blow insulation over vermiculite and we do not remove it.
It catches people out because it reads like an insulation rule and is really an electrical one. In the older houses of the peninsula and the inner suburbs it is worth checking before you take a quote seriously.
Of the 36 places on this site, Charleston County is the clearest: its building code names insulation as permit work, its sub-trade permit form lists fiberglass and spray foam insulation, and its FAQ excuses only a job under $1,000 that needs no inspection, done by the homeowner or a one-trade specialty contractor. That rule covers the unincorporated county and the towns whose permits the county issues, such as Seabrook Island, Awendaw, Meggett and Rockville. The City of Charleston, Folly Beach, Kiawah Island, Sullivan's Island, McClellanville, Hanahan, Hollywood and Ravenel publish rules that require a permit for alterations or repairs and list no exemption for insulation; Mount Pleasant does the same, except that work valued at no more than $1,000 needs no permit unless it calls for an inspection. In flood zones AE and VE the City of Charleston says all work on an existing home needs a permit, interior work included.
Everywhere else, the honest answer is that the city publishes no answer. We confirm it with the department before starting and pull whatever is required. Your city's page says exactly what that city publishes and nothing more.
South Carolina registers insulation installers rather than licensing them as a trade of their own. The Residential Builders Commission lists “insulation installers” among the residential specialty contractors (S.C. Code § 40-59-20), every residential specialty contractor must be registered with it for work over $500 (§ 40-59-220), and on a homeowner's job over $5,000 the contractor must carry a surety bond (§ 40-59-240). Commercial work over $10,000 needs a license from the Contractor's Licensing Board, where insulation falls under the Nonstructural Renovation subclassification. You can look a contractor up at llr.sc.gov.
State registration does not excuse anyone from local licensing, and the law says so (§ 40-59-240). Most cities and towns here require their own business license from every contractor working inside their limits, and Charleston County requires a county contractor license or registration and a decal on both sides of each work vehicle. Each town page says what that town publishes.
The programs have their own rules about who may do the work: Dominion's Check-up Plus uses only its own approved contractor, Berkeley Electric's loans use its approved contractors, and Santee Cooper pays only for work by its Trade Allies.
The code and the rebates decide the target; how the work is done is on each service page: attic insulation, spray foam insulation, crawl space insulation, basement insulation, garage insulation, insulation removal, energy audit, wall insulation and air sealing.
Municipal research 2026-10-24; energy code, rebate and climate research 2026-10-24. Rebate amounts carry the program year they were published under. Sources: scstatehouse.gov · llr.sc.gov · dominionenergy.com (2) · berkeleyelectric.coop (2, 3) · santeecooper.com · coastal.coop · cdn-dominionenergy-prd-001.azureedge.net · energy.sc.gov · irs.gov (2) · energy.gov · energystar.gov · ncei.noaa.gov · epa.gov · berkeleyca.gov. These change; confirm with the office or the utility first.
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