Marshall County, SD Insulation Payback
Marshall County, SD: what topping up your attic actually costs
Marshall 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. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-60 runs an estimated $3,480, and saves about $2,350 a year in heating and cooling — a payback around 1.5 years. That's about as fast as attic paybacks get.
Heating vs. cooling in Marshall County
The estimated savings split roughly $2,251/year heating, $99/year cooling. Out of every 100 US counties tracked here, Marshall County's savings potential beats roughly 94 of them. Within zone 6 specifically, it ranks 62nd of 459 counties by estimated savings. South Dakota averages $2,162/year across the counties tracked here; Marshall County comes in 9% higher.
Where these numbers come from
The heating and cooling degree days behind this estimate — 8,417 HDD and 619 CDD (base 65°F, 1991-2020 normals) — come from ROY LAKE, SD US, the nearest NOAA station with published normals, 7.4 miles from Marshall County's center. By total degree days, Marshall County sits at the 95th percentile nationally. Marshall County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
The smaller top-up scenario
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $343/year saved — roughly 6.7 years to break even. That is a solid payback as home upgrades go.
Getting it done in Marshall County
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 Marshall County's estimated $2,350/year on the line.
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-60 is the target here specifically.