Scott County, IL Insulation Payback
Attic insulation payback for Scott County, IL
DOE classifies Scott County as climate zone 5, cold — cold enough that heating, not cooling, is what decides the bill. Its recommended attic R-value for bare joists is 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 $1,648 a year — payback in roughly 2.1 years.
Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $1,467/year comes from reduced heating and $181/year from reduced cooling load through the ceiling. Scott County beats 63% of the counties in this 3,171-county dataset on estimated insulation savings. Among the 754 counties DOE places in zone 5, Scott County ranks 579th. Against Illinois's own average of $1,642/year, Scott County runs 0% above that.
Where these numbers come from
The heating and cooling degree days behind this estimate — 5,485 HDD and 1,130 CDD (base 65°F, 1991-2020 normals) — come from Winchester, IL US, the nearest NOAA station with published normals, 1.3 miles from Scott County's center. Combined heating and cooling load puts Scott County in the 64th percentile of this 3,171-county dataset. DOE also classifies Scott County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
The smaller top-up scenario
If Scott 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 $240/year — payback about 9.5 years. It is close - the payback only just fits a reasonable timeframe.
Getting it done in Scott County
Actual quotes will vary by attic access, existing debris, and whether the job needs air sealing first, so treat the $3,480 figure above as a planning number for Scott County, not a bid. Worth getting quotes from at least two local contractors before committing - most 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.