Spray Foam vs Fiberglass vs Blown-In: Which Is Best for Florida Homes?

Every Florida homeowner shopping for insulation hits the same fork: spray foam costs more upfront, fiberglass is cheap, and blown-in is in the middle. Which one actually makes sense when you live in a state where humidity tries to destroy everything?

We've installed all three across Lee, Collier and Charlotte counties since 2012. Here's the honest comparison.

The Quick Comparison

Why This Comparison Is Different in Florida

1. Humidity Is the Enemy

Southwest Florida averages 74% relative humidity. In summer, it's 85-95%. When warm, humid air hits a cool surface (your air-conditioned ceiling), condensation forms. Inside fiberglass insulation, that means mold growth, R-value collapse, and structural damage over time.

Spray foam — especially closed cell — doesn't absorb moisture. It seals the building envelope so humid air can't reach cool surfaces.

2. Your Attic Is an Oven

Southwest Florida attics run 130-140°F in summer. Your ductwork is up there, pumping 55°F air through ducts surrounded by 130-140°F air. Blown-in fiberglass on the attic floor tries to block heat, but your ducts still cook.

Open cell spray foam on the roof deck brings the attic inside the conditioned envelope, so it runs much closer to indoor temperature instead of 130-140°F. Ducts stay cool. Homeowners commonly report their AC cycling off in the afternoon instead of running until sundown.

Code sets the minimum at 5 inches of open cell at the deck — that's the R-30 unvented attic assembly we install in new construction. If you're staying with a vented attic and blowing the floor instead, we build to an R-38 target.

3. Hurricane Season Is Real

Closed cell spray foam sprayed against the roof deck bonds the sheathing to the trusses and adds structural strength to the roof assembly. It's also a vapor barrier. That combination is why builders spec it on coastal jobs.

When Each Type Makes Sense

Closed Cell Spray Foam — The Premium Choice

Best for: Crawl spaces, coastal homes, flood zones, garages, exterior walls. At R-6.5 per inch with a moisture barrier, it's the gold standard when moisture is the primary concern.

Open Cell Spray Foam — The Smart Middle Ground

Best for: Attic roof decks, interior walls, soundproofing, most residential applications. Excellent air seal at half the cost of closed cell. This is what we install in the majority of Naples attics.

Blown-In Fiberglass — The Budget Option

Best for: Supplementing existing insulation, flat attic floors on a tight budget, rental properties. Quick and cheap but doesn't air seal, settles over time, and holds moisture.

Fiberglass Batts — Economy Choice

Best for: Interior partition walls for soundproofing, and frame walls in new construction at R-13. Not recommended as a standalone attic solution in Florida — gaps at every stud, wire, and pipe let humid air through.

Install Cost and Service Life (1,500 sq ft attic)

Blown-in is the cheapest to install. Open cell costs about twice that, seals air instead of just slowing heat, and doesn't come back around on a replacement cycle — which is why it's what goes into most of the Naples attics we do. Your actual number comes off your county property-appraiser record, in writing, before anybody drives out.

Our Recommendation for Most SWFL Homes

1. Attic: Open cell spray foam at the roof deck, 5 inch minimum by code — the R-30 unvented assembly. Staying vented? Blow the floor to R-38.
2. Crawl spaces: Closed cell spray foam
3. Exterior walls (new construction): R-4.1 board on block walls, R-13 batts in frame walls, mineral wool at garage framing and wet areas
4. Interior walls: Fiberglass batts for sound dampening
5. Coastal/flood zone: Closed cell throughout

Still Not Sure?

Send us the address. We size the job off your county property-appraiser record and send back a written price — no site visit, no sales pitch at your kitchen table. You get a free pre-visit before we install, and most installs happen the same week, often within 48 hours.

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Ideal Insulation is a Naples-based insulation contractor serving Lee, Collier and Charlotte counties since 2012 — Naples, Fort Myers, Cape Coral, Bonita Springs, Estero, Marco Island, Lehigh Acres, Punta Gorda and Port Charlotte. Whether you need spray foam insulation, blown-in attic insulation, or insulation removal, we run 9 trucks and 20+ certified installers — all on payroll, no subcontracting.

Get a written price from your county property record or call (239) 455-2002. Se habla español.