Onslow County, NC Insulation Payback
Onslow County attic insulation, by the numbers
Onslow County, North Carolina is zone 3 under DOE's climate map (Hot-Humid), which means summers that stay hot and humid while winters barely register on the energy bill. An uninsulated attic there should be built up to R-49. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-49 runs an estimated $2,820, and saves about $1,034 a year in heating and cooling — a payback around 2.7 years. Topping up the attic pays for itself fast here.
Heating vs. cooling in Onslow County
Split it out and it's roughly $734 a year on the heating side, $300 on cooling. By estimated insulation savings, Onslow County lands in the 19th percentile nationally. Zone 3 alone covers 690 counties in this dataset, and Onslow County comes in 401st by savings. North Carolina averages $1,169/year across the counties tracked here; Onslow County comes in 12% lower.
Onslow County's actual weather, not a national average
Onslow County's climate figures — 2,767 heating and 1,880 cooling degree days a year — are read from JACKSONVILLE EOC, NC US, 6 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Onslow County sits at the 15th percentile nationally. One local detail the R-value alone won't tell you: Onslow County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
If the attic isn't bare
A shallower starting point changes the math: with R-11 already down, only the gap to R-38 needs filling, at roughly $1,620 for an estimated $139/year saved (~11.6-year payback). Call this borderline rather than a clear win.
Next steps for a Onslow County attic
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $2,820 as a starting estimate for a Onslow County job, not a quote. Expect at least a $600 minimum charge from most contractors.
Where these figures come from
Onslow County's R-49 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-49 is the target here specifically.