Fresno County, CA Insulation Payback
Fresno County attic insulation, by the numbers
Fresno County sits in IECC climate zone 3 (Hot-Dry) — intense summer heat with low humidity, where attic radiant heat gain is the main driver. For a currently uninsulated attic, DOE and ENERGY STAR recommend building up to R-49. For an attic around 1,000 square feet, closing the gap from R-2 to R-49 costs around $2,820 and saves an estimated $893 a year — payback in roughly 3.2 years. Topping up the attic pays for itself here.
Where the savings come from
Split it out and it's roughly $493 a year on the heating side, $400 on cooling. By estimated insulation savings, Fresno County lands in the 10th percentile nationally. Zone 3 alone covers 690 counties in this dataset, and Fresno County comes in 644th by savings. California averages $1,056/year across the counties tracked here; Fresno County comes in 15% lower.
Fresno County's actual weather, not a national average
The heating and cooling degree days behind this estimate — 1,858 HDD and 2,511 CDD (base 65°F, 1991-2020 normals) — come from FRESNO 5 NE, CA US, the nearest NOAA station with published normals, 3 miles from Fresno County's center. That combined heating-and-cooling load ranks Fresno County 2909th nationally by total degree days — the 8th percentile. One local detail the R-value alone won't tell you: Fresno County sits in moisture regime B (dry), which can affect the vapor-barrier choice.
The smaller top-up scenario
A shallower starting point changes the math: with R-11 already down, only the gap to R-38 needs filling, at roughly $1,620 for an estimated $120/year saved (~13.5-year payback). Call this borderline rather than a clear win.
Getting it done in Fresno County
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 Fresno County's estimated $893/year on the line.
Where these figures come from
Fresno County's R-49 target and its degree-day figures both come from named federal sources - see the methodology guide for exactly which ones. The guide to what R-value actually means explains why R-49 is the target here specifically.