Shelby County, IL Insulation Payback
Is attic insulation worth it in Shelby County, IL?
Shelby County sits in IECC climate zone 4 (Mixed-Humid) — real heating and real cooling seasons both, roughly balanced across the year. For a currently uninsulated attic, DOE and ENERGY STAR recommend building 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 $1,613 a year in heating and cooling — a payback around 2.2 years. Few home upgrades pay back that quickly.
Heating vs. cooling in Shelby County
Heating accounts for about $1,423/year of that and cooling about $190/year — Shelby County needs both. Nationally, Shelby County ranks in the 60th percentile for insulation savings potential. Compared only against its own climate zone, Shelby County places 39th out of 825. Against Illinois's own average of $1,642/year, Shelby County runs 2% below that.
Shelby County's actual weather, not a national average
Shelby County's climate figures — 5,321 heating and 1,186 cooling degree days a year — are read from SHELBYVILLE DAM, IL US, 2.1 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Shelby County sits at the 62th percentile nationally. Its moisture regime is classified humid, which matters for whether the attic needs a vapor retarder as part of the job — worth asking a contractor about locally.
Already have some insulation?
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $235/year saved — roughly 9.7 years to break even. Whether that is worth it depends on how long you plan to stay.
Getting it done in Shelby 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 Shelby County's estimated $1,613/year on the line.
Shelby County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Shelby County's numbers, and where the cost assumptions come from. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.