Duval County, FL Insulation Payback
Is attic insulation worth it in Duval County, FL?
DOE classifies Duval County as climate zone 2, hot-humid — summers that stay hot and humid while winters barely register on the energy bill. Its recommended attic R-value for bare joists is R-49. Topping up a typical 1,000-square-foot attic from bare joists (R-2) to R-49 runs an estimated $2,820, and saves about $777 a year in heating and cooling — a payback around 3.6 years. That is a solid payback as home upgrades go.
Heating vs. cooling in Duval County
Heating accounts for about $250/year of that and cooling about $526/year — Duval County needs both. Nationally, Duval County ranks in the 4th percentile for insulation savings potential. Compared only against its own climate zone, Duval County places 185th out of 233. Against Florida's own average of $743/year, Duval County runs 5% above that.
Where these numbers come from
NOAA's JACKSONVILLE NAS, FL US station, 7.1 miles from Duval County, supplies the 944 HDD and 3,303 CDD this estimate runs on. By total degree days, Duval County sits at the 5th percentile nationally. 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-38 needs filling, at roughly $1,620 for an estimated $105/year saved (~15.5-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 $2,820 figure above as a planning number for Duval County, not a bid - contractors typically charge a $600 minimum regardless of job size.
Duval County's numbers, sourced
The methodology guide lists exactly which DOE and NOAA sources feed Duval 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.