Clark County, IL Insulation Payback
Is attic insulation worth it in Clark County, IL?
Clark County sits in IECC climate zone 5 (Cold) — winters that dominate the energy bill, with cooling a minor factor. 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 $1,580 a year in heating and cooling — a payback around 2.2 years. Few home upgrades pay back that quickly.
The breakdown behind the number
Heating accounts for about $1,383/year of that and cooling about $197/year — Clark County needs both. Nationally, Clark County ranks in the 58th percentile for insulation savings potential. Compared only against its own climate zone, Clark County places 662nd out of 745. Against Illinois's own average of $1,642/year, Clark County runs 4% below that.
Clark County's actual weather, not a national average
NOAA's CASEY, IL US station, 10.1 miles from Clark County, supplies the 5,173 HDD and 1,228 CDD this estimate runs on. Combined heating and cooling load puts Clark County in the 60th percentile of this 3,162-county dataset. 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.
The smaller top-up scenario
If Clark 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 $231/year — payback about 9.9 years. Whether that is worth it depends on how long you plan to stay.
Getting it done in Clark 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 Clark County's estimated $1,580/year on the line.
Clark County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Clark 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.