Clay County, IL Insulation Payback
Attic insulation payback for Clay County, IL
Clay 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. 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 $1,534 a year — payback in roughly 2.3 years. Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $1,319/year comes from reduced heating and $215/year from reduced cooling load through the ceiling. Clay County beats 55% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 825 counties DOE places in zone 4, Clay County ranks 126th. Against Illinois's own average of $1,642/year, Clay County runs 7% below that.
Where these numbers come from
Clay County's climate figures — 4,933 heating and 1,337 cooling degree days a year — are read from FLORA, IL US, 4.8 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Clay County sits at the 57th percentile nationally. DOE also classifies Clay County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
Already have some insulation?
If Clay 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 $224/year — payback about 10.2 years. It is close - the payback only just fits a reasonable timeframe.
Quotes and materials for this job
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 Clay County, not a bid - contractors typically charge a $600 minimum regardless of job size.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.