Johnson County, GA Insulation Payback
Johnson County, GA: what topping up your attic actually costs
Johnson County, Georgia is zone 3 under DOE's climate map (Hot-Humid), which means humid heat for much of the year, with cooling running far more than heating ever does. An uninsulated attic there should be built up to R-49. For an attic around 1,000 square feet, closing the gap from R-2 to R-49 costs around $2,820 and saves an estimated $976 a year — payback in roughly 2.9 years. That's about as fast as attic paybacks get.
Heating vs. cooling in Johnson County
The estimated savings split roughly $645/year heating, $332/year cooling. Out of every 100 US counties tracked here, Johnson County's savings potential beats roughly 15 of them. Within zone 3 specifically, it ranks 524th of 690 counties by estimated savings. Georgia averages $974/year across the counties tracked here; Johnson County comes in 0% higher.
The climate data behind this
The heating and cooling degree days behind this estimate — 2,430 HDD and 2,081 CDD (base 65°F, 1991-2020 normals) — come from KITE, GA US, the nearest NOAA station with published normals, 7.2 miles from Johnson County's center. That combined heating-and-cooling load ranks Johnson County 2802nd nationally by total degree days — the 11th percentile. Johnson County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
If the attic isn't bare
Already have a few inches up there? Topping R-11 up to R-38 runs about $1,620 for about $132/year saved — roughly 12.3 years to break even. This one is a genuine toss-up, not a clear yes.
Next steps for a Johnson 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 Johnson County's estimated $976/year on the line.
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-49 is the target here specifically.