Thurston County, WA Insulation Payback
Thurston County, WA: what topping up your attic actually costs
Thurston County sits in IECC climate zone 4 (Marine) — mild, damp weather year-round with modest heating load and little cooling. 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 $1,456 a year in heating and cooling — a payback around 2.4 years. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $1,438/year heating, $18/year cooling. Out of every 100 US counties tracked here, Thurston County's savings potential beats roughly 50 of them. Within zone 4 specifically, it ranks 268th of 825 counties by estimated savings. Washington averages $1,583/year across the counties tracked here; Thurston County comes in 8% lower.
The climate data behind this
Thurston County's climate figures — 5,378 heating and 113 cooling degree days a year — are read from OLYMPIA AP, WA US, 4.3 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Thurston County sits at the 39th percentile nationally. Thurston County falls in DOE's moisture regime C (marine), a detail that affects vapor-barrier recommendations more than the R-value target itself.
If the attic isn't bare
If Thurston 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 $212/year — payback about 10.7 years. This one is a genuine toss-up, not a clear yes.
Quotes and materials for this job
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 Thurston County, not a bid - contractors typically charge a $600 minimum regardless of job size.
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-60 is the target here specifically.