Marshall County, IL Insulation Payback
Marshall County attic insulation, by the numbers
Marshall County, Illinois is zone 5 under DOE's climate map (Cold), which means a real winter that drives most of the annual energy bill here. 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 $1,680 a year in heating and cooling — a payback around 2.1 years. Topping up the attic pays for itself fast here.
Heating vs. cooling in Marshall County
Split it out and it's roughly $1,498 a year on the heating side, $182 on cooling. By estimated insulation savings, Marshall County lands in the 65th percentile nationally. Zone 5 alone covers 745 counties in this dataset, and Marshall County comes in 519th by savings. Illinois averages $1,642/year across the counties tracked here; Marshall County comes in 2% higher.
Where these numbers come from
The heating and cooling degree days behind this estimate — 5,603 HDD and 1,134 CDD (base 65°F, 1991-2020 normals) — come from LACON, IL US, the nearest NOAA station with published normals, 3.9 miles from Marshall County's center. Combined heating and cooling load puts Marshall County in the 67th percentile of this 3,162-county dataset. One local detail the R-value alone won't tell you: Marshall County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
Already have some insulation?
A shallower starting point changes the math: with R-11 already down, only the gap to R-49 needs filling, at roughly $2,280 for an estimated $245/year saved (~9.3-year payback). Call this borderline rather than a clear win.
Next steps for a Marshall County attic
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 Marshall County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Marshall 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.