Attic insulation, air sealing, crawl spaces and walls for homes in Unincorporated Charleston County — starting with a free assessment that measures the R-value you actually have. Unincorporated Charleston County enforces the 2009 IECC (state law), which sets R-30 for a new attic.
This page covers the parts of the county that are not inside a city — where the county, not a municipality, runs building and permits. The Census does not publish population or housing totals for that remainder on its own, so this page does not quote any: the figures you will see elsewhere for “Charleston County” include every municipality in it as well.
For Charleston County as a whole, municipalities included, the Census Bureau's 2020–2024 estimates give a median year built of 1991, with 5% of its 209,803 homes built before 1940. The unincorporated remainder has no figures of its own.
We have not logged a completed job in Unincorporated Charleston County yet. We would rather say so than put a number on this page that is not real.
Unincorporated Charleston County enforces the South Carolina Energy Standard (the 2009 IECC), by state law. The county lists the 2009 International Energy Conservation Code with the 2021 residential code, and its own building ordinance, Ordinance 2283 of March 26, 2024, sets the local permit, fee, inspection and contractor rules.
That edition sets R-30 for the attic in new work, and R-13 for walls. The Department of Energy's recommendation for this climate zone runs higher: R49 for an attic with nothing in it, R38 where a few inches are already down.
Table 402.1.1 of the 2009 IECC, climate zone 3, which South Carolina's Energy Standard Act adopts for the whole state (section 6-10-30 of the South Carolina Code).
Unincorporated Charleston County requires a permit for this work. Charleston County's building code lists insulation among the jobs that need their own permit, and the county's sub-trade permit form names "Insulation (fiberglass, spray foam)". The county FAQ excuses only jobs under $1,000 that need no inspection when the homeowner does the work, or when a single-trade specialty contractor does it; "otherwise, permits are required for all trades and work no matter the value.". We pull it as part of the job.
The published number is 843-202-6930. The department page is here.
Permitting is on us, not on you.
Berkeley Electric Cooperative's own territory map shows its service reaching into Unincorporated Charleston County, and Dominion Energy South Carolina also serves Charleston County, so the name on the electric bill decides which program applies. Dominion Energy South Carolina's Check-up Plus is the big one: 90% of attic insulation, air sealing and duct sealing paid, up to $2,880, until March 31, 2027, for electrically heated homes that have had the free check-up, with the work done by Dominion's approved contractor.
Berkeley Electric lends rather than rebates: its HomeAdvantage program lends up to $20,000 at 5%, with an energy audit first and the payments added to the electric bill. Income-qualified households can apply to Palmetto Community Action Partnership (843-720-5336) for free weatherization instead. Every condition attached is on the Charleston County page and in the rebate guide.
Every layer of an insulated attic, explained
Elsewhere in Charleston County we also cover:
South Carolina sets the residential energy code statewide, so the attic figure is R-30 wherever it is published here; what changes is the permit desk, and 7 of the 7 publish a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Unincorporated Charleston County | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Adams Run | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Awendaw | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Charleston | 2009 IECC (state law) | R-30 | Yes | 843-577-5550 |
| Edisto Island | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Folly Beach | 2009 IECC (state law) | R-30 | Yes | 843-588-2447 |
| Hollywood | 2009 IECC (state law) | R-30 | Yes | 864-586-6111 |
All 22 Charleston County jurisdictions side by side →
Unincorporated Charleston County enforces the 2009 IECC (state law), which sets R-30 for an attic in new work. Whether it reaches a retrofit of an existing house is not published.
Yes. Unincorporated Charleston County requires a permit for this work, and we pull it as part of the job.
Dominion Energy South Carolina's Check-up Plus pays 90% of attic insulation, air sealing and duct sealing, up to $2,880, until March 31, 2027, for electrically heated homes; the program's contractor does the work. Berkeley Electric members get a 5% on-bill loan instead of a rebate. The federal 25C credit ended for work placed in service after December 31, 2025.
Code and permit facts checked October 24, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: charlestoncounty.gov (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23) · scstatehouse.gov · llr.sc.gov (2) · dominionenergy.com · berkeleyelectric.coop · santeecooper.com · coastal.coop · energystar.gov. These change; confirm with the building department at 843-202-6930 or the utility named on your electric bill first.
Free assessment, a measured R-value, and photos you keep either way.
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