Oconee County, SC Insulation Payback
Oconee County attic insulation, by the numbers
Oconee County, South Carolina is zone 3 under DOE's climate map (Mixed-Humid), which means a genuine mix of cold winters and humid summers, with neither one dominating the bill. An uninsulated attic there should be built up to R-49. For an attic around 1,000 square feet, closing the gap from R-2 to R-49 costs around $2,820 and saves an estimated $1,147 a year — payback in roughly 2.5 years. Topping up the attic pays for itself fast here.
Where the savings come from
Split it out and it's roughly $924 a year on the heating side, $222 on cooling. By estimated insulation savings, Oconee County lands in the 27th percentile nationally. Zone 3 alone covers 690 counties in this dataset, and Oconee County comes in 167th by savings. South Carolina averages $1,016/year across the counties tracked here; Oconee County comes in 13% higher.
The climate data behind this
The heating and cooling degree days behind this estimate — 3,483 HDD and 1,396 CDD (base 65°F, 1991-2020 normals) — come from WALHALLA, SC US, the nearest NOAA station with published normals, 0.9 miles from Oconee County's center. Combined heating and cooling load puts Oconee County in the 22th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Oconee County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
The smaller top-up scenario
If Oconee County's attic already has 3-4 inches of old insulation (about R-11) rather than bare joists, the recommended target drops to R-38. That smaller top-up costs around $1,620 and saves an estimated $154/year — payback about 10.5 years. Call this borderline rather than a clear win.
Quotes and materials for this job
Get more than one quote before committing. Attic access and any needed air sealing move the price around, and most contractors won't take a job below roughly $600 regardless of size - worth asking upfront given Oconee County's estimated $1,147/year on the line.
Where these figures come from
Oconee County's R-49 target and its degree-day figures both come from named federal sources - see the methodology guide for exactly which ones. The guide to what R-value actually means explains why R-49 is the target here specifically.