Fergus County, MT Insulation Payback
Fergus County attic insulation, by the numbers
Fergus County, Montana 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 $1,974 a year in heating and cooling — a payback around 1.8 years. Topping up the attic pays for itself fast here.
Where the savings come from
Split it out and it's roughly $1,904 a year on the heating side, $70 on cooling. By estimated insulation savings, Fergus County lands in the 81th percentile nationally. Zone 6 alone covers 459 counties in this dataset, and Fergus County comes in 415th by savings. Montana averages $2,182/year across the counties tracked here; Fergus County comes in 10% lower.
The climate data behind this
Fergus County's climate figures — 7,121 heating and 435 cooling degree days a year — are read from LEWISTOWN, MT US, 13.4 miles away, NOAA's nearest 1991-2020 normals station. Combined heating and cooling load puts Fergus County in the 80th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Fergus County sits in moisture regime B (dry), which can affect the vapor-barrier choice.
Already have some insulation?
If Fergus 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 $288/year — payback about 7.9 years. Worth doing on the numbers alone.
Getting it done in Fergus 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 Fergus County's estimated $1,974/year on the line.
Where these figures come from
Fergus 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.