Plymouth County, IA Insulation Payback
Attic insulation payback for Plymouth County, IA
DOE classifies Plymouth County as climate zone 6, cold — winters that dominate the energy bill, with cooling a minor factor. Its recommended attic R-value for bare joists is 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 $2,077 a year in heating and cooling — a payback around 1.7 years. Hard to find a home improvement with a faster payback than this.
The breakdown behind the number
Of that, about $1,955/year comes from reduced heating and $121/year from reduced cooling load through the ceiling. Plymouth County beats 86% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 459 counties DOE places in zone 6, Plymouth County ranks 317th. Against Iowa's own average of $1,985/year, Plymouth County runs 5% above that.
Where these numbers come from
Plymouth County's climate figures — 7,312 heating and 756 cooling degree days a year — are read from LE MARS, IA US, 4.7 miles away, NOAA's nearest 1991-2020 normals station. By total degree days, Plymouth County sits at the 87th percentile nationally. DOE also classifies Plymouth County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
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 $303/year saved (~7.5-year payback). Topping up the attic pays for itself here.
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 Plymouth County, not a bid - contractors typically charge a $600 minimum regardless of job size.
More on how this was built
Nothing here is a guess: the methodology guide names the DOE climate map and NOAA station data behind every number on this page. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.