Carter County, TN Insulation Payback
Carter County attic insulation, by the numbers
Carter County, Tennessee is zone 4 under DOE's climate map (Mixed-Humid), which means a genuine mix of cold winters and humid summers, with neither one dominating the bill. 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 2.7 years at an estimated $1,312/year saved. Topping up the attic pays for itself fast here.
Heating vs. cooling in Carter County
Split it out and it's roughly $1,151 a year on the heating side, $162 on cooling. By estimated insulation savings, Carter County lands in the 39th percentile nationally. Zone 4 alone covers 825 counties in this dataset, and Carter County comes in 561st by savings. Tennessee averages $1,258/year across the counties tracked here; Carter County comes in 4% higher.
Where these numbers come from
The heating and cooling degree days behind this estimate — 4,303 HDD and 1,008 CDD (base 65°F, 1991-2020 normals) — come from ELIZABETHTON, TN US, the nearest NOAA station with published normals, 8.3 miles from Carter County's center. That combined heating-and-cooling load ranks Carter County 2058th nationally by total degree days — the 35th percentile. One local detail the R-value alone won't tell you: Carter County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
Already have some insulation?
If Carter 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 $191/year — payback about 11.9 years. Call this borderline rather than a clear win.
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 Carter County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Carter 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.