Kalawao County, HI Insulation Payback
Kalawao County, HI: what topping up your attic actually costs
Kalawao County, Hawaii is zone 1 under DOE's climate map (Hot-Humid), which means summers that stay hot and humid while winters barely register on the energy bill. An uninsulated attic there should be built up to R-30. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-30 runs an estimated $1,680, and saves about $617 a year in heating and cooling — a payback around 2.7 years. That's about as fast as attic paybacks get.
Where the savings come from
The estimated savings split roughly $0/year heating, $617/year cooling. Out of every 100 US counties tracked here, Kalawao County's savings potential beats roughly 1 of them. Within zone 1 specifically, it ranks 58th of 81 counties by estimated savings. Hawaii averages $808/year across the counties tracked here; Kalawao County comes in 24% lower.
The climate data behind this
The heating and cooling degree days behind this estimate — 0 HDD and 3,981 CDD (base 65°F, 1991-2020 normals) — come from MOLOKAI AP, HI US, the nearest NOAA station with published normals, 9 miles from Kalawao County's center. That combined heating-and-cooling load ranks Kalawao County 3090th nationally by total degree days — the 2th percentile. Kalawao County falls in DOE's moisture regime A (humid), a detail that affects vapor-barrier recommendations more than the R-value target itself.
Already have some insulation?
Already have a few inches up there? Topping R-11 up to R-25 runs about $840 for about $67/year saved — roughly 12.5 years to break even. This one is a genuine toss-up, not a clear yes.
Getting it done in Kalawao County
Real bids depend on how easy the attic is to reach and whether old insulation needs removing first, so treat $1,680 as a starting estimate for a Kalawao County job, not a quote. Expect at least a $600 minimum charge from most contractors.
Nothing here is a guess
Every figure on this page traces to DOE/IECC climate zones and NOAA degree-day normals, documented in the methodology guide. The guide to what R-value actually means explains why R-30 is the target here specifically.