Washington County, ID Insulation Payback
Washington County attic insulation, by the numbers
Washington County sits in IECC climate zone 5 (Cold) — winters that dominate the energy bill, with cooling a minor factor. 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 $1,912 a year in heating and cooling — a payback around 1.8 years. Topping up the attic pays for itself fast here.
Heating vs. cooling in Washington County
Split it out and it's roughly $1,801 a year on the heating side, $111 on cooling. By estimated insulation savings, Washington County lands in the 78th percentile nationally. Zone 5 alone covers 745 counties in this dataset, and Washington County comes in 132nd by savings. Idaho averages $1,995/year across the counties tracked here; Washington County comes in 4% lower.
Washington County's actual weather, not a national average
NOAA's CAMBRIDGE, ID US station, 10.5 miles from Washington County, supplies the 6,734 HDD and 693 CDD this estimate runs on. By total degree days, Washington County sits at the 78th percentile nationally. One local detail the R-value alone won't tell you: Washington County sits in moisture regime B (dry), which can affect the vapor-barrier choice.
The smaller top-up scenario
If Washington 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 $279/year — payback about 8.2 years. Call this borderline rather than a clear win.
Next steps for a Washington 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 Washington County's estimated $1,912/year on the line.
Where these figures come from
Washington 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.