Knox County, IL Insulation Payback
Knox County attic insulation, by the numbers
Knox County, Illinois is zone 5 under DOE's climate map (Cold), which means cold enough that heating, not cooling, is what decides the bill. An uninsulated attic there should be built up to R-60. Going from R-2 to the recommended R-60 costs roughly $3,480 installed for a typical attic (about 1,000 sq ft), and pays for itself in about 1.9 years at an estimated $1,800/year saved. Topping up the attic pays for itself fast here.
The breakdown behind the number
Split it out and it's roughly $1,655 a year on the heating side, $144 on cooling. By estimated insulation savings, Knox County lands in the 72th percentile nationally. Zone 5 alone covers 745 counties in this dataset, and Knox County comes in 292nd by savings. Illinois averages $1,642/year across the counties tracked here; Knox County comes in 10% higher.
Where these numbers come from
Knox County's climate figures — 6,191 heating and 899 cooling degree days a year — are read from KNOXVILLE, IL US, 4.4 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Knox County sits at the 73th percentile nationally. One local detail the R-value alone won't tell you: Knox County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
Already have some insulation?
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $263/year saved — roughly 8.7 years to break even. Call this borderline rather than a clear win.
Quotes and materials for this job
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $3,480 as a starting estimate for a Knox County job, not a quote. Expect at least a $600 minimum charge from most contractors.
Where these figures come from
Knox 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.