Jefferson County, ID Insulation Payback
Jefferson County, ID: what topping up your attic actually costs
DOE classifies Jefferson County as climate zone 6, cold — cold enough that heating, not cooling, is what decides the bill. Its recommended attic R-value for bare joists is R-60. For an attic around 1,000 square feet, closing the gap from R-2 to R-60 costs around $3,480 and saves an estimated $2,186 a year — payback in roughly 1.6 years. That's about as fast as attic paybacks get.
The breakdown behind the number
The estimated savings split roughly $2,137/year heating, $49/year cooling. Out of every 100 US counties tracked here, Jefferson County's savings potential beats roughly 90 of them. Within zone 6 specifically, it ranks 199th of 459 counties by estimated savings. Idaho averages $1,995/year across the counties tracked here; Jefferson County comes in 10% higher.
Jefferson County's actual weather, not a national average
Jefferson County's climate figures — 7,992 heating and 308 cooling degree days a year — are read from HAMER 4 NW, ID US, 12 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks Jefferson County 350th nationally by total degree days — the 89th percentile. Jefferson County falls in DOE's moisture regime B (dry), a detail that affects vapor-barrier recommendations more than the R-value target itself.
If the attic isn't bare
If Jefferson 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 $319/year — payback about 7.1 years. That is a solid payback as home upgrades go.
Quotes and materials for this job
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 Jefferson County's estimated $2,186/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-60 is the target here specifically.