Marshall County, IA Insulation Payback
Attic insulation payback for Marshall County, IA
Marshall County sits in IECC climate zone 5 (Cold) — cold enough that heating, not cooling, is what decides the bill. 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 $2,008 a year — payback in roughly 1.7 years. Hard to find a home improvement with a faster payback than this.
Where the savings come from
Of that, about $1,887/year comes from reduced heating and $121/year from reduced cooling load through the ceiling. Marshall County beats 83% of the counties in this 3,162-county dataset on estimated insulation savings. Among the 745 counties DOE places in zone 5, Marshall County ranks 39th. Against Iowa's own average of $1,985/year, Marshall County runs 1% above that.
Marshall County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 7,056 HDD and 753 CDD (base 65°F, 1991-2020 normals) — come from MARSHALLTOWN, IA US, the nearest NOAA station with published normals, 3.3 miles from Marshall County's center. Combined heating and cooling load puts Marshall County in the 83th percentile of this 3,162-county dataset. DOE also classifies Marshall County as moisture regime A (humid) - ask a local contractor whether that changes the vapor-barrier approach for this job.
Already have some insulation?
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 $293/year saved (~7.8-year payback). Topping up the attic pays for itself here.
Next steps for a Marshall 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 Marshall County's estimated $2,008/year on the line.
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.