Attic insulation, air sealing, crawl spaces and walls for homes in Charleston — starting with a free assessment that measures the R-value you actually have. The typical home here dates to the mid-1990s, and 10% of its 77,417 homes went up before 1940.
Charleston runs to about 115 square miles and roughly 154,338 people. That is roughly 77,417 housing units. The community dates back to 1783. We cover ZIP codes 29401, 29403, 29405, 29407, 29412, 29414, 29455 and 29492.
Our job history shows nothing in Charleston so far. Plenty of sites will show you a number here anyway.
The typical home in Charleston dates to around the mid-1990s. Houses of this vintage usually got batts or blown fiber at whatever the standard of the day was, which is well short of what is recommended now. Most are one top-up away from being right.
The historic peninsula is known for 18th- and 19th-century houses of wood, brick and stucco, many of them Charleston single houses, while Hampton Park Terrace on the upper peninsula was built mostly between 1914 and 1922 in Prairie, Foursquare, Colonial Revival, Craftsman and bungalow styles.
We work across Charleston rather than one corner of it — Ansonborough, Harleston Village, French Quarter, Radcliffeborough, Cannonborough/Elliottborough, Wraggborough, East Side, Westside, Wagener Terrace and Hampton Park Terrace 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.
Founded in 1670 and incorporated as Charleston in 1783, the city's peninsula holds one of the country's richest collections of 18th- and 19th-century houses, including the Charleston single house, one room deep with its narrow end to the street. The Old and Historic District, created in 1931, was the first historic district in the United States protected by local law. Beyond the peninsula the city takes in West Ashley, much of James Island, part of Johns Island, Daniel Island and the Cainhoy peninsula.
The Census Bureau estimates 77,417 homes in Charleston. 7,753 of them (10%) went up before 1940 — the 4th-highest share of pre-1940 housing among the 28 places on this site. The 2010s were the busiest decade, adding 17,224 of today's homes (22%); 34% predate 1980 and 45% were built in 2000 or later. For Charleston County as a whole the pre-1940 share is 5%, so Charleston sits above it.
Of 68,027 occupied homes, 25% heat with utility gas and 73% with electricity. Electric heat here is less common than across the county (76%), and ranks 23rd of 28 on this site. Which utility program can contribute depends on the heating fuel and on who sends the bill, so that is the first thing an assessment pins down.
56% of occupied homes are owner-occupied and 48% of all homes are single-family detached houses, with 643 mobile homes in the count. With houses like these, the conversations we expect most are about air sealing on newer houses that already have depth and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 7,753 | 10% | |
| 1940s | 2,465 | 3% | |
| 1950s | 4,473 | 6% | |
| 1960s | 6,146 | 8% | |
| 1970s | 5,797 | 7% | |
| 1980s | 8,395 | 11% | |
| 1990s | 7,496 | 10% | |
| 2000s | 14,513 | 19% | |
| 2010s | 17,224 | 22% | |
| 2020 or later | 3,155 | 4% |
77,417 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 68,027 occupied.
15,891 of Charleston's 77,417 homes (21%) were built in the 1980s and 1990s. The gaps in houses of that age are the parts nobody sealed: batts stuffed into the rim joist, bare spots over cathedral and tray ceilings, soffit vents buried with no baffles, can lights punched through the ceiling plane. A top-up plus a day of sealing usually covers it.
Charleston enforces the South Carolina Energy Standard (the 2009 IECC), by state law. The city's Building Inspections page lists the 2009 International Energy Conservation Code beside the 2021 South Carolina Residential Code and the 2020 National Electrical Code, with no local amendments.
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).
Charleston requires a permit for this work. The city's own guidance says "a permit must be obtained from Building Inspections for any work being done in the City of Charleston," and its residential alteration permit lists an insulation inspection. In flood zones AE and VE the city adds that all work on an existing home needs a permit, including non-structural interior work. 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.
Berkeley Electric Cooperative's own territory map shows its service reaching into Charleston, and Dominion Energy South Carolina also serves Charleston County, so the name on the electric bill decides which program applies. 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. The Charleston County page and the rebate guide carry the full rules.
Every layer of an insulated attic, explained
Charleston borders North Charleston, Mount Pleasant, James Island, Johns Island, Goose Creek and Ashley River. 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 4 of the 7 publish a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Charleston | 2009 IECC (state law) | R-30 | Yes | 843-577-5550 |
| North Charleston | 2009 IECC (state law) | R-30 | Not published | 843-740-2562 |
| Mount Pleasant | 2009 IECC (state law) | R-30 | Yes | 843-884-5184 |
| James Island | 2009 IECC (state law) | R-30 | Not published | 843-795-4141 |
| Johns Island | 2009 IECC (state law) | R-30 | Yes | 843-577-5550 |
| Goose Creek | 2009 IECC (state law) | R-30 | Not published | 843-797-6220 ext. 1508 |
| Adams Run | 2009 IECC (state law) | R-30 | Yes | 843-202-6930 |
All 22 Charleston County jurisdictions side by side →
Charleston 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. Charleston 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.
The typical home in Charleston dates to around the mid-1990s; the Census Bureau's 2020-2024 median year built is 1995. Of its 77,417 homes, 10% went up before 1940 and 45% in 2000 or later. That is a median across the whole place, so your own house may be older or newer.
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, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24) · scstatehouse.gov · en.wikipedia.org (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14) · scencyclopedia.org · nationalregister.sc.gov (2, 3, 4, 5) · gis.charleston-sc.gov · www2.census.gov · dominionenergy.com · berkeleyelectric.coop · santeecooper.com · coastal.coop · energystar.gov · data.census.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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