Shelby County, IA Insulation Payback
Shelby County, IA: what topping up your attic actually costs
DOE classifies Shelby County as climate zone 5, cold — winters that dominate the energy bill, with cooling a minor factor. 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 $1,909 a year — payback in roughly 1.8 years.
That's about as fast as attic paybacks get.
The breakdown behind the number
The estimated savings split roughly $1,756/year heating, $154/year cooling. Out of every 100 US counties tracked here, Shelby County's savings potential beats roughly 78 of them. Within zone 5 specifically, it ranks 139th of 754 counties by estimated savings. Iowa averages $1,985/year across the counties tracked here; Shelby County comes in 4% lower.
Where these numbers come from
NOAA's Harlan, IA US station, 2.7 miles from Shelby County, supplies the 6,566 HDD and 957 CDD this estimate runs on. By total degree days, Shelby County sits at the 80th percentile nationally. Shelby County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
The smaller top-up scenario
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 $279/year saved (~8.2-year payback). This one is a genuine toss-up, not a clear yes.
Getting it done in Shelby County
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 Shelby County's estimated $1,909/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.