In this guide
The short answer
R-38 is the recommended attic insulation level for Florida (climate zones 1–2). How deep that is depends on the material: about 13–16″ of blown fiberglass, ~11″ of cellulose, or ~6″ of closed-cell spray foam. Most Florida homes were built below R-38, so reaching it usually means a top-off to the target depth.
What R-38 means
R-value measures resistance to heat flow — the higher the number, the more the insulation slows heat moving through it. R-38 is a target level of total thermal resistance for your attic, not a thickness. The thickness needed to reach it depends entirely on the material.
Why R-38 for Florida?
The U.S. Department of Energy places Florida in climate zones 1–2 and recommends R-38 for attics. In Florida the payoff is almost entirely about cooling: keeping 130–150°F attic heat from radiating into your living space so your AC runs less. Learn more in the Florida Attic Heat guide.
How deep is R-38?
There's no single depth — it varies by material, and even by product, so the manufacturer's coverage chart is the exact spec:
- Blown fiberglass (~R-2.2–2.7/in): about 13–16″.
- Blown cellulose (~R-3.2–3.8/in): about 10–12″.
- Open-cell spray foam (~R-3.6/in): about 10–11″.
- Closed-cell spray foam (~R-6–7/in): about 5.5–6.5″.
Check your current level with the Depth → R-Value Calculator (it lets you pick your material).
R-30 vs R-38
R-30 is an older minimum; R-38 is the current recommendation. In blown fiberglass that's roughly 12″ vs 13–16″ — only a few extra inches. Because the crew is already on site, the upgrade to R-38 is a small added cost for savings that recur every cooling season. Compare them for your home with the R-30 vs R-38 Calculator.
What it costs to reach R-38
For most Florida homes, reaching R-38 with blown-in insulation runs $1,400–$3,000 — see the cost guide for the drivers, or your size-specific range in the cost calculator.
See your home's exact numbers — price, R-value, and savings — with a free Florida Attics quote in under 60 seconds. No salesperson, no obligation.
Get My Free Quote →Frequently asked questions
Is R-38 enough for Florida?
Yes — R-38 is the DOE-recommended attic level for Florida's climate zones and the standard Florida Attics installs to. Going higher offers diminishing returns for most homes.
How many inches is R-38?
About 13–16 inches of blown fiberglass, ~11 inches of cellulose, or ~6 inches of closed-cell spray foam. It depends on the material's R-per-inch and the specific product.
My attic is R-19 — how much do I add for R-38?
Enough to add roughly R-19 more. In blown fiberglass that's about 7–8 inches on top of what you have. The Depth → R-Value calculator gives your exact gap.
Is R-49 or R-60 better than R-38 in Florida?
Higher R-values add some benefit but with diminishing returns in Florida's mild winters. R-38 is the recommended balance of cost and performance for most Florida attics.
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