Multnomah County, OR Insulation Payback
Is attic insulation worth it in Multnomah County, OR?
Multnomah County, Oregon is zone 4 under DOE's climate map (Marine), which means mild, damp weather year-round with modest heating load and little cooling. An uninsulated attic there should be built up to 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 3 years at an estimated $1,180/year saved. Few home upgrades pay back that quickly.
Heating vs. cooling in Multnomah County
Heating accounts for about $1,111/year of that and cooling about $69/year — Multnomah County needs both. Nationally, Multnomah County ranks in the 30th percentile for insulation savings potential. Compared only against its own climate zone, Multnomah County places 768th out of 825. Against Oregon's own average of $1,557/year, Multnomah County runs 24% below that.
Multnomah County's actual weather, not a national average
Multnomah County's climate figures — 4,155 heating and 427 cooling degree days a year — are read from PORTLAND TROUTDALE AP, OR US, 0.5 miles away, NOAA's nearest 1991-2020 normals station. That combined heating-and-cooling load ranks Multnomah County 2745th nationally by total degree days — the 13th percentile. Its moisture regime is classified marine, which matters for whether the attic needs a vapor retarder as part of the job — worth asking a contractor about locally.
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 $172/year saved (~13.3-year payback). Whether that is worth it depends on how long you plan to stay.
Quotes and materials for this job
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $3,480 as a starting estimate for a Multnomah County job, not a quote. Expect at least a $600 minimum charge from most contractors.
Multnomah County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Multnomah 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.