Day County, SD Insulation Payback
Day County attic insulation, by the numbers
DOE classifies Day County as climate zone 6, cold — cold enough that heating, not cooling, is what decides the bill. Its recommended attic R-value for bare joists is R-60. Going from R-2 to the recommended R-60 costs roughly $3,480 installed for a typical attic (about 1,000 sq ft), and pays for itself in about 1.5 years at an estimated $2,384/year saved. Topping up the attic pays for itself fast here.
Where the savings come from
Split it out and it's roughly $2,299 a year on the heating side, $85 on cooling. By estimated insulation savings, Day County lands in the 95th percentile nationally. Zone 6 alone covers 459 counties in this dataset, and Day County comes in 38th by savings. South Dakota averages $2,162/year across the counties tracked here; Day County comes in 10% higher.
Day County's actual weather, not a national average
NOAA's WEBSTER, SD US station, 3.2 miles from Day County, supplies the 8,598 HDD and 529 CDD this estimate runs on. Combined heating and cooling load puts Day County in the 96th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Day County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
Already have some insulation?
If Day County's attic already has 3-4 inches of old insulation (about R-11) rather than bare joists, the recommended target drops to R-49. That smaller top-up costs around $2,280 and saves an estimated $348/year — payback about 6.6 years. Worth doing on the numbers alone.
Quotes and materials for this job
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $3,480 as a starting estimate for a Day County job, not a quote. Expect at least a $600 minimum charge from most contractors.
Where these figures come from
Day County's R-60 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-60 is the target here specifically.