Lee County, IL Insulation Payback
Lee County, IL: what topping up your attic actually costs
Lee County, Illinois is zone 5 under DOE's climate map (Cold), which means winters that dominate the energy bill, with cooling a minor factor. An uninsulated attic there should be built 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 $1,928 a year — payback in roughly 1.8 years. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $1,817/year heating, $112/year cooling. Out of every 100 US counties tracked here, Lee County's savings potential beats roughly 79 of them. Within zone 5 specifically, it ranks 114th of 745 counties by estimated savings. Illinois averages $1,642/year across the counties tracked here; Lee County comes in 17% higher.
The climate data behind this
The heating and cooling degree days behind this estimate — 6,794 HDD and 695 CDD (base 65°F, 1991-2020 normals) — come from COMPTON 1 NW, IL US, the nearest NOAA station with published normals, 10.7 miles from Lee County's center. That combined heating-and-cooling load ranks Lee County 660th nationally by total degree days — the 79th percentile. Lee County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
If the attic isn't bare
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $281/year saved — roughly 8.1 years to break even. This one is a genuine toss-up, not a clear yes.
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 Lee County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Nothing here is a guess
Every figure on this page traces to DOE/IECC climate zones and NOAA degree-day normals, documented in the methodology guide. The guide to what R-value actually means explains why R-60 is the target here specifically.