Montgomery County, IL Insulation Payback
Is attic insulation worth it in Montgomery County, IL?
DOE classifies Montgomery County as climate zone 4, mixed-humid — a genuine mix of cold winters and humid summers, with neither one dominating the bill. Its recommended attic R-value for bare joists is 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 2.3 years at an estimated $1,506/year saved. Few home upgrades pay back that quickly.
Heating vs. cooling in Montgomery County
Heating accounts for about $1,283/year of that and cooling about $223/year — Montgomery County needs both. Nationally, Montgomery County ranks in the 53th percentile for insulation savings potential. Compared only against its own climate zone, Montgomery County places 164th out of 825. Against Illinois's own average of $1,642/year, Montgomery County runs 8% below that.
The climate data behind this
NOAA's HILLSBORO, IL US station, 4.7 miles from Montgomery County, supplies the 4,799 HDD and 1,389 CDD this estimate runs on. That combined heating-and-cooling load ranks Montgomery County 1397th nationally by total degree days — the 56th percentile. Its moisture regime is classified humid, which matters for whether the attic needs a vapor retarder as part of the job — worth asking a contractor about locally.
The smaller top-up scenario
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $220/year saved — roughly 10.4 years to break even. Whether that is worth it depends on how long you plan to stay.
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 Montgomery County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Montgomery County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Montgomery County's numbers, and where the cost assumptions come from. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.