Knox County, TN Insulation Payback
Attic insulation payback for Knox County, TN
Knox County sits in IECC climate zone 4 (Mixed-Humid) — a genuine mix of cold winters and humid summers, with neither one dominating the bill. For a currently uninsulated attic, DOE and ENERGY STAR recommend building 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 2.8 years at an estimated $1,265/year saved. Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $1,046/year comes from reduced heating and $219/year from reduced cooling load through the ceiling. Knox County beats 36% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 825 counties DOE places in zone 4, Knox County ranks 648th. Against Tennessee's own average of $1,258/year, Knox County runs 1% above that.
Knox County's actual weather, not a national average
NOAA's KNOXVILLE EXP STN, TN US station, 6.6 miles from Knox County, supplies the 3,911 HDD and 1,364 CDD this estimate runs on. By total degree days, Knox County sits at the 33th percentile nationally. DOE also classifies Knox County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
If the attic isn't bare
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). It is close - the payback only just fits a reasonable timeframe.
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 Knox County, not a bid - contractors typically charge a $600 minimum regardless of job size.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.