Arlington County, VA Insulation Payback
Arlington County attic insulation, by the numbers
DOE classifies Arlington 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. 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 $1,287 a year in heating and cooling — a payback around 2.7 years. Topping up the attic pays for itself fast here.
Where the savings come from
Split it out and it's roughly $1,008 a year on the heating side, $279 on cooling. By estimated insulation savings, Arlington County lands in the 37th percentile nationally. Zone 4 alone covers 825 counties in this dataset, and Arlington County comes in 611th by savings. Virginia averages $1,342/year across the counties tracked here; Arlington County comes in 4% lower.
The climate data behind this
Arlington County's climate figures — 3,769 heating and 1,738 cooling degree days a year — are read from WASHINGTON REAGAN AP, VA US, 4.1 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks Arlington County 1901st nationally by total degree days — the 40th percentile. One local detail the R-value alone won't tell you: Arlington 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-49 needs filling, at roughly $2,280 for an estimated $188/year saved (~12.1-year payback). Call this borderline rather than a clear win.
Getting it done in Arlington County
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 Arlington County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Where these figures come from
Arlington 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.