Washtenaw County, MI Insulation Payback
Is attic insulation worth it in Washtenaw County, MI?
Washtenaw County sits in IECC climate zone 5 (Cold) — winters that dominate the energy bill, with cooling a minor factor. 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 $1,886 a year — payback in roughly 1.8 years. Few home upgrades pay back that quickly.
Where the savings come from
Heating accounts for about $1,803/year of that and cooling about $84/year — Washtenaw County needs both. Nationally, Washtenaw County ranks in the 77th percentile for insulation savings potential. Compared only against its own climate zone, Washtenaw County places 161st out of 745. Against Michigan's own average of $2,064/year, Washtenaw County runs 9% below that.
The climate data behind this
The heating and cooling degree days behind this estimate — 6,742 HDD and 520 CDD (base 65°F, 1991-2020 normals) — come from ANN ARBOR MUNI AP, MI US, the nearest NOAA station with published normals, 5.5 miles from Washtenaw County's center. Combined heating and cooling load puts Washtenaw County in the 76th percentile of this 3,162-county dataset. Its moisture regime is classified humid, which matters for whether the attic needs a vapor retarder as part of the job — worth asking a contractor about locally.
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 $275/year saved (~8.3-year payback). Whether that is worth it depends on how long you plan to stay.
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 Washtenaw County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Washtenaw County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Washtenaw County's numbers, and where the cost assumptions come from. See the DIY vs. contractor guide for whether a job this size is realistic to do yourself.