Sac County, IA Insulation Payback
Sac County, IA: what topping up your attic actually costs
Sac County sits in IECC climate zone 6 (Cold) — a real winter that drives most of the annual energy bill here. For a currently uninsulated attic, DOE and Energy Star recommend building up to 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 $2,081 a year — payback in roughly 1.7 years.
That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $1,971/year heating, $110/year cooling. Out of every 100 US counties tracked here, Sac County's savings potential beats roughly 86 of them. Within zone 6 specifically, it ranks 314th of 459 counties by estimated savings. Iowa averages $1,985/year across the counties tracked here; Sac County comes in 5% higher.
Where these numbers come from
The heating and cooling degree days behind this estimate — 7,371 HDD and 683 CDD (base 65°F, 1991-2020 normals) — come from SAC City, IA US, the nearest NOAA station with published normals, 6.9 miles from Sac County's center. That combined heating-and-cooling load ranks Sac County 435th nationally by total degree days — the 86th percentile. Sac County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
If the attic isn't bare
If Sac 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 $303/year — payback about 7.5 years. That is a solid payback as home upgrades go.
Quotes and materials for this job
Get quotes from at least two local contractors 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 checking upfront given Sac County's estimated $2,081/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.