Insulation and air sealing for Johns Island homes: attics, crawl spaces, rim joists and walls, starting with a free assessment of the R-value you actually have. Johns Island enforces the 2009 IECC (state law), which sets R-30 for a new attic.
We cover ZIP code 29455.
We have not logged a completed job in Johns Island yet. We would rather say so than put a number on this page that is not real.
Mostly rural land with farms and historic settlement communities; about ten new subdivisions were planned and approved inside the urban growth boundary by 2007, and the population grew by half between 2000 and 2010.
We work across Johns Island rather than one corner of it — Red Top, Exchange Landing, Cape, Hut, Whaley, Stevens, Brownswood Place, Sea Island Place and Dunmovin/Island Estates included. Construction and vintage change between them, sometimes by thirty years and a whole different framing method, which decides whether a wall can be dense-packed at all.
Johns Island is the largest island in South Carolina, a rural sea island of farms, tree-lined roads and saltwater wetlands, home of the Angel Oak. About a third of it lies in the City of Charleston, which steers new subdivisions inside an urban growth boundary, while most of the island is unincorporated county land. City planning for the island calls for laying out new development around low-lying areas to avoid flooding.
Johns Island enforces the South Carolina Energy Standard (the 2009 IECC), by state law. City and county land sit side by side on the island, and the city's Building Inspections page and Charleston County's code list both name the 2009 International Energy Conservation Code.
For new work, the attic number under that edition is R-30, with walls at R-13. Set that against the Department of Energy, which recommends R49 for an uninsulated attic in this climate zone and R38 for one that already has a few inches.
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).
Johns Island requires a permit for this work. The City of Charleston says a permit from Building Inspections is needed for any work in the city, and Charleston County's building code lists insulation among the jobs that need their own permit. The county waives it only for jobs under $1,000 that need no inspection and are done by the homeowner or a one-trade specialty contractor. We pull it as part of the job.
The published number is 843-577-5550. The department page is here.
Permitting is on us, not on you.
Part of Johns Island sits inside Berkeley Electric Cooperative's territory, by the cooperative's own map, and Dominion Energy South Carolina is also on record in Charleston County: check whose name is on the electric bill first. If Dominion Energy South Carolina sends the bill and the house heats with electricity, Check-up Plus covers 90% of an attic, air sealing and duct sealing job, to $2,880, through March 31, 2027; it starts with Dominion's free check-up and uses the program's own 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
Johns Island borders West Ashley, James Island, Wadmalaw Island, Seabrook Island, Kiawah Island and Edisto Island. These are the ones we also cover, each with its own energy code and permit rule:
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 6 of the 7 publish a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Johns Island | 2009 IECC (state law) | R-30 | Yes | 843-577-5550 |
| West Ashley | 2009 IECC (state law) | R-30 | Yes | 843-577-5550 |
| James Island | 2009 IECC (state law) | R-30 | Not published | 843-795-4141 |
| Wadmalaw Island | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Seabrook Island | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
| Kiawah Island | 2009 IECC (state law) | R-30 | Yes | 843-768-9166 |
| Edisto Island | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
All 22 Charleston County jurisdictions side by side →
Johns Island 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. Johns Island 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: charleston-sc.gov (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) · charlestoncounty.gov (2, 3, 4, 5, 6, 7, 8, 9, 10) · scstatehouse.gov · charlestoncounty.org · en.wikipedia.org (2, 3) · scdah.sc.gov · gis.charleston-sc.gov · www2.census.gov · dominionenergy.com · berkeleyelectric.coop · santeecooper.com · coastal.coop · energystar.gov. These change; confirm with the building department at 843-577-5550 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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