What a home energy assessment in a Charleston house measures, how the attic check and the blower door work, which utilities send someone for free, and how the findings turn into a short, priced list of fixes.
Most people book an assessment because a bill or a room has stopped making sense: the upstairs bedroom that never cools down, the power bill that jumps every July, the hallway that smells like the crawl space after a wet week. Those are symptoms. The assessment is the visit that traces them to a cause before anyone tries to sell you a cure.
In a Charleston house the causes usually sit in three places: the attic, where the summer heat and very often the ductwork live; the gaps between the house and the outdoors, which let the damp air in; and the floor or crawl space underneath. Ours costs nothing, the R-value is measured rather than guessed, and the report and the photographs stay with you whether you hire us or not.
NOAA's 1991-2020 normals for Charleston International Airport show a cooling load of about 2,434 degree days each year, well ahead of the 1,844 on the heating side, and 64 days that reach 90°F. The state climate office's August table puts average relative humidity in Charleston at 79 percent. So an attic here does its hardest work on summer afternoons, and the outside air that slips in through gaps arrives loaded with water the air conditioner then has to wring out.
Heating still shows up on the bill. The Census Bureau's 2020-2024 survey finds electricity heating between 75 and 77 percent of occupied homes, county by county, with utility gas close to one home in five. How a house is heated matters twice: it decides what a fix will save, and with Dominion Energy South Carolina it decides whether the largest insulation offer in the area is open to you at all.
A price written from the curb skips every one of those questions. We would rather measure first and quote second.
The attic gets the longest look. Blown insulation is rarely even, so its depth is measured in several spots, and the material is identified so the inches can be turned into an R-value. ENERGY STAR offers a check you can make yourself from the hatch: insulation level with the tops of the floor joists, or below them, usually means the attic needs more. South Carolina's energy standard, the 2009 IECC adopted for the whole state by S.C. Code 6-10-30, asks R-30 of a new ceiling in climate zone 3. ENERGY STAR recommends R-38 where a few inches are already down and R-49 where the attic starts empty.
Under the insulation we look for the openings that matter more than depth: chases around flues and plumbing stacks, the tops of interior walls, recessed lights, the hatch itself. Then the ductwork. In many houses here the air handler and its ducts sit in the attic, the hottest spot on the property in July. The 2009 code wants supply ducts in an attic sealed and wrapped to R-8 in new work; an older system can have crushed runs, open joints or a loose boot dumping cooled air into the attic. We photograph it and say who should repair it, since duct work belongs to the heating and cooling trade.
The test uses a calibrated fan mounted in an exterior door frame. The Building America Solution Center, which the Department of Energy runs, describes the usual practice: the fan pulls the house down to 50 pascals below the outdoors, and the volume of air it must move to keep the house there is the leakage figure, reported in cubic feet per minute as CFM50. Divided by the house's volume it becomes ACH50, air changes per hour at that pressure, which lets a small cottage and a large house be compared fairly.
The number matters less than what the fan makes possible. While it runs, leaks can be found by hand and with an infrared camera, and once the sealing is finished the same test shows how much the work really cut. That pair of readings is the fair way to judge an air sealing job, and on jobs that need a number, both go in your report.
Getting a house ready takes a few minutes: windows shut and latched, a gas water heater turned down to its pilot setting, fireplace ashes cleared out or covered. The guide also warns that pulling an older house down to test pressure can draw mold, asbestos or old insulation out of walls, attics and crawl spaces into the rooms. That is why the attic and the crawl space are looked at before the fan goes in the door, and why a house with suspect material gets a different plan.
The floor gets the same attention as the ceiling. Over a vented crawl space we check the insulation between the joists, the ground cover, any standing water, and the rim joist, where outside air often moves most freely. In a raised house on open piers the underside of the floor is effectively outdoors, and whatever holds the insulation up matters as much as its R-value. ENERGY STAR recommends R-19 for a floor in zone 3, the same figure South Carolina's code sets for a new floor.
Humidity is part of the visit here, not an afterthought. EPA advises keeping indoor relative humidity below 60 percent, ideally between 30 and 50, and getting wet materials dry inside 24 to 48 hours so mold never gets started. Sweating ductwork, a damp subfloor, a musty closet on an outside wall: each points at air or water getting where it should not, and each changes what we would put first on the list.
In a mapped flood zone a crawl space may have to keep its flood vents open, which rules out some sealed crawl space designs. The crawl space page goes through that; the assessment is where it gets noticed.
Tightening a house changes how it breathes. ENERGY STAR cautions that a tighter house may need mechanical ventilation to keep the indoor air healthy, and that gas appliances venting by natural draft can backdraft once the house is sealed and the exhaust fans run. With about one occupied home in five on utility gas across the three counties, plus a few percent on propane, every gas water heater, furnace and fireplace is noted before any sealing is proposed.
Two more checks matter most in older houses. Loose, pebble-like flakes in the attic, gray-brown or silver-gold, may be vermiculite, which EPA says to assume contains asbestos and to leave undisturbed; we stop there and do not blow insulation over it. Cloth-covered wire running on porcelain knobs is knob-and-tube, which Article 394.12 of the National Electrical Code does not allow buried in loose, rolled or foamed-in-place insulation. The state applies the 2020 edition of the NEC everywhere, with the 2023 edition due on January 1, 2027. Either finding changes the order of the job, and an electrician comes before the insulation.
Several of the utilities serving the three counties send someone out at no charge. They are worth knowing about, because one of them is the door to real money.
If you are a Dominion electric customer with electric heat, book Dominion's check-up as well as ours. If the house qualifies for the 90 percent offer, that is very likely the cheaper road for the attic, and we will say so.
The visit ends with numbers rather than a pitch. The written report gives the attic R-value as measured, the figure we would build to and why, the leakage reading where one was taken, and the photographs: the attic floor, the duct joints, the crawl space, the hatch. Then a short list of fixes in a sensible order, which in this climate usually means sealing the ceiling and dealing with obvious duct faults before adding depth.
Each item on the list carries its own price, and the program question is answered alongside it: whether the address is on Dominion, a cooperative or Santee Cooper, what that utility offers this year, and whether the household might qualify for free weatherization through Palmetto Community Action Partnership instead. The federal 25C credit plays no part in a 2026 number, because it stopped with property placed in service by the end of 2025.
If the house turns out to be in good shape, the report says that too; some are. The code and rebate guide explains the state figures, and every town page lists its own permit desk.
Yes, it costs nothing. The written report and the photographs are yours to keep whether you hire us or not, and you are free to take them to another contractor or to a utility program. They show what is in the attic and under the floor today, measured, with the fixes listed in order.
Plan on about an hour for most houses, longer when there is a crawl space to get into or a blower door test to run. Someone needs to be home to let us into the attic and under the floor, and to answer a few questions about the bills and how the house is heated and cooled.
If Dominion Energy South Carolina sends your electric bill, do both. Its check-up is the required first step for Check-up Plus, which until March 31, 2027 covers 90 percent of an attic, air sealing and duct sealing job in an electrically heated home, to a maximum of $2,880. Ours measures and prices the work for the many houses that do not qualify.
No. It is a fan in a doorway that lowers the indoor pressure slightly for a few minutes. The Department of Energy's Building America guide does warn that depressurizing an older house can pull dust or old insulation into the rooms, which is why the attic and the crawl space are checked before the test is run.
Then the report says so. A well-insulated attic over a sealed ceiling is not unusual in the newer subdivisions of Berkeley and Dorchester counties, where the median home was built around 2000. Sometimes the real trouble is the ductwork or a bath fan venting into the attic, and you will hear that instead of an insulation price.
Energy audit across greater Charleston, from the peninsula and the sea islands out to Summerville, Goose Creek and Moncks Corner. Each city has its own page with the permit rule and code edition that apply there:
Sources: NOAA 1991-2020 normals, Charleston International Airport (degree days, days at 90F) · SC State Climatology Office: August relative humidity, Charleston (79%) · Census ACS 2020-2024: house heating fuel by county (B25040) · Census ACS 2020-2024: year built and median year built (B25034, B25035) · South Carolina Energy Standard Act (2009 IECC adopted statewide) · 2009 IECC for South Carolina (Insulation Institute): zone 3 ceiling R-30, floor R-19, attic supply ducts R-8 · ENERGY STAR recommended R-values, zone 3 · ENERGY STAR DIY checks: the joist test · ENERGY STAR attic air sealing project: ventilation and backdrafting cautions · Building America Solution Center: enclosure leakage (blower door) test · EPA: a brief guide to mold, moisture and your home · EPA: vermiculite insulation · NEC 394.12(5) knob-and-tube text, as reproduced by the City of Berkeley · SC Building Codes Council, 2024 code adoption notice (2023 NEC from January 1, 2027) · Dominion Energy SC Home Energy Check-up and Check-up Plus · Berkeley Electric Cooperative: request an energy audit · Berkeley Electric Cooperative HomeAdvantage loan · Santee Cooper Home Energy House Call · Coastal Electric Cooperative home energy checkup · Edisto Electric Cooperative energy audit · Palmetto Community Action Partnership weatherization · IRS: Energy Efficient Home Improvement Credit (25C) ended after 2025. Codes, programs and prices change; confirm the current rule with your city before you rely on it.
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