Marshall County, TN Insulation Payback
Attic insulation payback for Marshall County, TN
Marshall 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 $1,245 a year in heating and cooling — a payback around 2.8 years. Hard to find a home improvement with a faster payback than this.
The breakdown behind the number
Of that, about $993/year comes from reduced heating and $252/year from reduced cooling load through the ceiling. Marshall County beats 34% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 825 counties DOE places in zone 4, Marshall County ranks 695th. Against Tennessee's own average of $1,258/year, Marshall County runs 1% below that.
Marshall County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 3,714 HDD and 1,568 CDD (base 65°F, 1991-2020 normals) — come from LEWISBURG EXP STN, TN US, the nearest NOAA station with published normals, 4.5 miles from Marshall County's center. Combined heating and cooling load puts Marshall County in the 34th percentile of this 3,162-county dataset. DOE also classifies Marshall 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
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $182/year saved — roughly 12.6 years to break even. It is close - the payback only just fits a reasonable timeframe.
Next steps for a Marshall County attic
Get more than one quote before committing. Attic access and any needed air sealing move the price around, and most contractors won't take a job below roughly $600 regardless of size - worth asking upfront given Marshall County's estimated $1,245/year on the line.
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.