Grant County, SD Insulation Payback
Grant County attic insulation, by the numbers
Grant County, South Dakota is zone 6 under DOE's climate map (Cold), which means winters that dominate the energy bill, with cooling a minor factor. An uninsulated attic there should be built up to R-60. For an attic around 1,000 square feet, closing the gap from R-2 to R-60 costs around $3,480 and saves an estimated $2,337 a year — payback in roughly 1.5 years. Topping up the attic pays for itself fast here.
Where the savings come from
Split it out and it's roughly $2,260 a year on the heating side, $78 on cooling. By estimated insulation savings, Grant County lands in the 94th percentile nationally. Zone 6 alone covers 459 counties in this dataset, and Grant County comes in 74th by savings. South Dakota averages $2,162/year across the counties tracked here; Grant County comes in 8% higher.
The climate data behind this
NOAA's MILBANK, SD US station, 8.2 miles from Grant County, supplies the 8,452 HDD and 483 CDD this estimate runs on. Combined heating and cooling load puts Grant County in the 94th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Grant County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $341/year saved — roughly 6.7 years to break even. Worth doing on the numbers alone.
Quotes and materials for this job
Actual quotes will vary by attic access, existing debris, and whether the job needs air sealing first. Treat the $3,480 figure above as a planning number for Grant County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Grant 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.