McDonough County, IL Insulation Payback
McDonough County, IL: what topping up your attic actually costs
McDonough County, Illinois is zone 5 under DOE's climate map (Cold), which means a real winter that drives most of the annual energy bill here. 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 2 years at an estimated $1,737/year saved. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $1,574/year heating, $163/year cooling. Out of every 100 US counties tracked here, McDonough County's savings potential beats roughly 68 of them. Within zone 5 specifically, it ranks 412th of 745 counties by estimated savings. Illinois averages $1,642/year across the counties tracked here; McDonough County comes in 6% higher.
McDonough County's actual weather, not a national average
McDonough County's climate figures — 5,886 heating and 1,017 cooling degree days a year — are read from PRAIRIE CITY 2S, IL US, 14.7 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks McDonough County 975th nationally by total degree days — the 69th percentile. McDonough County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
Already have some insulation?
If McDonough 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 $253/year — payback about 9 years. This one is a genuine toss-up, not a clear yes.
Next steps for a McDonough County attic
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 McDonough 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.