Mercer County, IL Insulation Payback
Mercer County attic insulation, by the numbers
Mercer County sits in IECC climate zone 5 (Cold) — a real winter that drives most of the annual energy bill here. For a currently uninsulated attic, DOE and Energy Star recommend building 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 $1,829 a year — payback in roughly 1.9 years.
Topping up the attic pays for itself fast here.
Heating vs. cooling in Mercer County
Split it out and it's roughly $1,687 a year on the heating side, $142 on cooling. By estimated insulation savings, Mercer County lands in the 74th percentile nationally. Zone 5 alone covers 754 counties in this dataset, and Mercer County comes in 245th by savings. Illinois averages $1,642/year across the counties tracked here; Mercer County comes in 11% higher.
Mercer County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 6,309 HDD and 885 CDD (base 65°F, 1991-2020 normals) — come from Aledo, IL US, the nearest NOAA station with published normals, 0.6 miles from Mercer County's center. That combined heating-and-cooling load ranks Mercer County 793rd nationally by total degree days — the 75th percentile. One local detail the R-value alone won't tell you: Mercer County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
If Mercer 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 $267/year — payback about 8.5 years. Call this borderline rather than a clear win.
Next steps for a Mercer County attic
Get quotes from at least two local contractors 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 checking upfront given Mercer County's estimated $1,829/year on the line.
Where these figures come from
Mercer 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.