McCormick County, SC Insulation Payback
Attic insulation payback for McCormick County, SC
DOE classifies McCormick County as climate zone 3, mixed-humid — a genuine mix of cold winters and humid summers, with neither one dominating the bill. Its recommended attic R-value for bare joists is 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 $1,060 a year — payback in roughly 2.7 years. Hard to find a home improvement with a faster payback than this.
Heating vs. cooling in McCormick County
Of that, about $749/year comes from reduced heating and $311/year from reduced cooling load through the ceiling. McCormick County beats 21% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 690 counties DOE places in zone 3, McCormick County ranks 335th. Against South Carolina's own average of $1,016/year, McCormick County runs 4% above that.
Where these numbers come from
NOAA's MCCORMICK, SC US station, 1.9 miles from McCormick County, supplies the 2,822 HDD and 1,954 CDD this estimate runs on. That combined heating-and-cooling load ranks McCormick County 2560th nationally by total degree days — the 19th percentile. DOE also classifies McCormick County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
The smaller top-up scenario
Already have a few inches up there? Topping R-11 up to R-38 runs about $1,620 for about $143/year saved — roughly 11.3 years to break even. It is close - the payback only just fits a reasonable timeframe.
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 McCormick County's estimated $1,060/year on the line.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.