Franklin County, TN Insulation Payback
Franklin County, TN: what topping up your attic actually costs
Franklin County sits in IECC climate zone 4 (Mixed-Humid) — real heating and real cooling seasons both, roughly balanced across the year. For a currently uninsulated attic, DOE and ENERGY STAR recommend building up to R-60. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-60 runs an estimated $3,480, and saves about $1,175 a year in heating and cooling — a payback around 3 years. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $941/year heating, $234/year cooling. Out of every 100 US counties tracked here, Franklin County's savings potential beats roughly 29 of them. Within zone 4 specifically, it ranks 774th of 825 counties by estimated savings. Tennessee averages $1,258/year across the counties tracked here; Franklin County comes in 7% lower.
Where these numbers come from
Franklin County's climate figures — 3,520 heating and 1,454 cooling degree days a year — are read from WINCHESTER 5SE, TN US, 3.8 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Franklin County sits at the 25th percentile nationally. Franklin 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 Franklin 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 $171/year — payback about 13.3 years. This one is a genuine toss-up, not a clear yes.
Next steps for a Franklin 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 Franklin 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.