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.
| Factor | Closed Cell Spray Foam | Open Cell Spray Foam | Blown-In Fiberglass | Fiberglass Batts |
|---|---|---|---|---|
| R-Value Per Inch | R-6.5 | R-3.7 | R-2.5 | R-3.1 |
| Air Sealing | Yes | Yes | No | No |
| Moisture Barrier | Yes | No | No | No |
| Cost Per Sq Ft | $2-4 | $1-2 | $0.50-1.25 | $0.30-1.00 |
| Lifespan | 20+ years | 20+ years | 10-15 years | 10-15 years |
| Mold Resistance | Excellent | Good | Poor | Poor |
| Hurricane Resistance | Adds structural strength | Minimal | None | None |
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.
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.
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.
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.
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.
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.
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.
| Blown-In | Open Cell Foam | Closed Cell Foam | |
|---|---|---|---|
| Install cost | $1,125 | $2,250 | $4,500 |
| Needs replacement? | Yes (10-15 yrs) | No | No |
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.
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.
Want someone to walk the house first? Book a free energy audit.
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.