Grundy County, IA Insulation Payback
Grundy County attic insulation, by the numbers
DOE classifies Grundy 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. Going from R-2 to the recommended R-60 costs roughly $3,480 installed for a typical attic (about 1,000 sq ft), and pays for itself in about 1.7 years at an estimated $2,050/year saved. Topping up the attic pays for itself fast here.
Heating vs. cooling in Grundy County
Split it out and it's roughly $1,932 a year on the heating side, $117 on cooling. By estimated insulation savings, Grundy County lands in the 84th percentile nationally. Zone 6 alone covers 459 counties in this dataset, and Grundy County comes in 350th by savings. Iowa averages $1,985/year across the counties tracked here; Grundy County comes in 3% higher.
Grundy County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 7,227 HDD and 730 CDD (base 65°F, 1991-2020 normals) — come from GRUNDY CTR, IA US, the nearest NOAA station with published normals, 3.1 miles from Grundy County's center. By total degree days, Grundy County sits at the 85th percentile nationally. One local detail the R-value alone won't tell you: Grundy County sits in moisture regime A (humid), which can affect the vapor-barrier choice.
The smaller top-up scenario
Already have a few inches up there? Topping R-11 up to R-49 runs about $2,280 for about $299/year saved — roughly 7.6 years to break even. Worth doing on the numbers alone.
Next steps for a Grundy 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 Grundy County's estimated $2,050/year on the line.
Where these figures come from
Grundy 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.