Franklin County, MO Insulation Payback
Franklin County attic insulation, by the numbers
DOE classifies Franklin County as climate zone 4, mixed-humid — a genuine mix of cold winters and humid summers, with neither one dominating the bill. 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 $1,415 a year — payback in roughly 2.5 years. Topping up the attic pays for itself fast here.
Heating vs. cooling in Franklin County
Split it out and it's roughly $1,176 a year on the heating side, $239 on cooling. By estimated insulation savings, Franklin County lands in the 47th percentile nationally. Zone 4 alone covers 825 counties in this dataset, and Franklin County comes in 355th by savings. Missouri averages $1,534/year across the counties tracked here; Franklin County comes in 8% lower.
The climate data behind this
Franklin County's climate figures — 4,400 heating and 1,485 cooling degree days a year — are read from UNION, MO US, 4.3 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks Franklin County 1609th nationally by total degree days — the 49th percentile. One local detail the R-value alone won't tell you: Franklin County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
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 $206/year — payback about 11 years. Call this borderline rather than a clear win.
Quotes and materials for this job
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 Franklin County's estimated $1,415/year on the line.
Where these figures come from
Franklin 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.