Shelby County, KY Insulation Payback
Shelby County attic insulation, by the numbers
DOE classifies Shelby County as climate zone 4, mixed-humid — real heating and real cooling seasons both, roughly balanced across the year. 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 $1,533/year saved. Topping up the attic pays for itself fast here.
The breakdown behind the number
Split it out and it's roughly $1,376 a year on the heating side, $157 on cooling. By estimated insulation savings, Shelby County lands in the 55th percentile nationally. Zone 4 alone covers 825 counties in this dataset, and Shelby County comes in 130th by savings. Kentucky averages $1,385/year across the counties tracked here; Shelby County comes in 11% higher.
Shelby County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 5,147 HDD and 976 CDD (base 65°F, 1991-2020 normals) — come from SHELBYVILLE 1 E, KY US, the nearest NOAA station with published normals, 3.1 miles from Shelby County's center. That combined heating-and-cooling load ranks Shelby County 1441st nationally by total degree days — the 54th percentile. One local detail the R-value alone won't tell you: Shelby County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
If Shelby 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 $224/year — payback about 10.2 years. Call this borderline rather than a clear win.
Getting it done in Shelby County
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 Shelby County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Shelby 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.