Martin County, FL Insulation Payback
Martin County, FL: what topping up your attic actually costs
DOE classifies Martin 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. Going from R-2 to the recommended R-49 costs roughly $2,820 installed for a typical attic (about 1,000 sq ft), and pays for itself in about 4.3 years at an estimated $652/year saved. The math clears comfortably within a normal ownership horizon.
Heating vs. cooling in Martin County
The estimated savings split roughly $89/year heating, $562/year cooling. Out of every 100 US counties tracked here, Martin County's savings potential beats roughly 1 of them. Within zone 2 specifically, it ranks 232nd of 233 counties by estimated savings. Florida averages $743/year across the counties tracked here; Martin County comes in 12% lower.
Where these numbers come from
The heating and cooling degree days behind this estimate — 337 HDD and 3,528 CDD (base 65°F, 1991-2020 normals) — come from PORT SALERNO 5W, FL US, the nearest NOAA station with published normals, 8.4 miles from Martin County's center. That combined heating-and-cooling load ranks Martin County 3112th nationally by total degree days — the 2th percentile. Martin 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?
If Martin County's attic already has 3-4 inches of old insulation (about R-11) rather than bare joists, the recommended target drops to R-38. That smaller top-up costs around $1,620 and saves an estimated $88/year — payback about 18.5 years. This one is a genuine toss-up, not a clear yes.
Quotes and materials for this job
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 Martin County's estimated $652/year on the line.
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-49 is the target here specifically.