Sangamon County, IL Insulation Payback
Sangamon County, IL: what topping up your attic actually costs
Sangamon County sits in IECC climate zone 5 (Cold) — winters that dominate the energy bill, with cooling a minor factor. For a currently uninsulated attic, DOE and ENERGY STAR recommend building 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 2.1 years at an estimated $1,634/year saved. That's about as fast as attic paybacks get.
Heating vs. cooling in Sangamon County
The estimated savings split roughly $1,459/year heating, $176/year cooling. Out of every 100 US counties tracked here, Sangamon County's savings potential beats roughly 62 of them. Within zone 5 specifically, it ranks 599th of 745 counties by estimated savings. Illinois averages $1,642/year across the counties tracked here; Sangamon County comes in 0% higher.
Where these numbers come from
Sangamon County's climate figures — 5,455 heating and 1,094 cooling degree days a year — are read from SPRINGFIELD #2, IL US, 2.9 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks Sangamon County 1186th nationally by total degree days — the 63th percentile. Sangamon 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
A shallower starting point changes the math: with R-11 already down, only the gap to R-49 needs filling, at roughly $2,280 for an estimated $238/year saved (~9.6-year payback). This one is a genuine toss-up, not a clear yes.
Getting it done in Sangamon County
Get more than one quote before committing. Attic access and any needed air sealing move the price around, and most contractors won't take a job below roughly $600 regardless of size - worth asking upfront given Sangamon County's estimated $1,634/year on the line.
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.