Kershaw County, SC Insulation Payback
Kershaw County, SC: what topping up your attic actually costs
Kershaw County, South Carolina is zone 3 under DOE's climate map (Mixed-Humid), which means heating load in winter and cooling load in summer, both worth taking seriously here. An uninsulated attic there should be built up to R-49. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-49 runs an estimated $2,820, and saves about $1,055 a year in heating and cooling — a payback around 2.7 years. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $732/year heating, $323/year cooling. Out of every 100 US counties tracked here, Kershaw County's savings potential beats roughly 21 of them. Within zone 3 specifically, it ranks 344th of 690 counties by estimated savings. South Carolina averages $1,016/year across the counties tracked here; Kershaw County comes in 4% higher.
The climate data behind this
Kershaw County's climate figures — 2,759 heating and 2,024 cooling degree days a year — are read from WATEREE DAM, SC US, 6.4 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Kershaw County sits at the 19th percentile nationally. Kershaw County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
Already have some insulation?
A shallower starting point changes the math: with R-11 already down, only the gap to R-38 needs filling, at roughly $1,620 for an estimated $142/year saved (~11.4-year payback). This one is a genuine toss-up, not a clear yes.
Getting it done in Kershaw County
Actual quotes will vary by attic access, existing debris, and whether the job needs air sealing first. Treat the $2,820 figure above as a planning number for Kershaw County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Nothing here is a guess
Every figure on this page traces to DOE/IECC climate zones and NOAA degree-day normals, documented in the methodology guide. The guide to what R-value actually means explains why R-49 is the target here specifically.