Rutherford County, TN Insulation Payback
Rutherford County, TN: what topping up your attic actually costs
DOE classifies Rutherford 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. For an attic around 1,000 square feet, closing the gap from R-2 to R-60 costs around $3,480 and saves an estimated $1,261 a year — payback in roughly 2.8 years. That's about as fast as attic paybacks get.
The breakdown behind the number
The estimated savings split roughly $1,007/year heating, $254/year cooling. Out of every 100 US counties tracked here, Rutherford County's savings potential beats roughly 36 of them. Within zone 4 specifically, it ranks 660th of 825 counties by estimated savings. Tennessee averages $1,258/year across the counties tracked here; Rutherford County comes in 0% higher.
Rutherford County's actual weather, not a national average
NOAA's MURFREESBORO 5 N, TN US station, 5.9 miles from Rutherford County, supplies the 3,765 HDD and 1,582 CDD this estimate runs on. By total degree days, Rutherford County sits at the 36th percentile nationally. Rutherford 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?
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 $184/year saved (~12.4-year payback). This one is a genuine toss-up, not a clear yes.
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 Rutherford 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.