Spray Foam vs. Fiberglass Insulation: Which Is Best for Florida Homes?

R-Value: The Starting Point

R-value measures a material's resistance to heat flow — the higher, the better. Fiberglass batts offer approximately R-2.9 to R-3.8 per inch, while open-cell spray foam delivers about R-3.7 per inch and closed-cell spray foam achieves R-6.0 to R-6.5 per inch.

On paper, the difference looks modest for open-cell foam vs. fiberglass. But here's what that number doesn't tell you: fiberglass batts only deliver their rated R-value under laboratory conditions with no air movement. In the real world, any air leaks around, through, or past the batts reduce the effective R-value dramatically — sometimes by 40–50% or more.

Air Sealing: The Game-Changer

This is where spray foam wins decisively. Spray foam expands to fill every crack, gap, and penetration in your wall or attic assembly, creating a continuous air barrier that fiberglass simply cannot replicate. According to the U.S. Department of Energy, air infiltration accounts for 25–40% of the energy used for heating and cooling in most homes.

In Florida, where your AC may run 8–10 months a year, sealing that air infiltration is the single most impactful thing you can do for your energy bills. Homeowners who switch from fiberglass to spray foam regularly report 30–50% reductions in their FPL bills.

Moisture Management in Florida's Humid Climate

Florida averages 54 inches of rainfall per year and relative humidity regularly exceeds 90% in the summer months. Fiberglass insulation has a significant weakness in humid climates: it absorbs moisture. Wet fiberglass loses much of its R-value and becomes a breeding ground for mold, mildew, and the bacteria that cause musty odors.

Closed-cell spray foam is completely impermeable to moisture — it acts as a Class II vapor retarder and physically blocks water from reaching your wall assembly. Open-cell foam is permeable (moisture passes through), which is actually an advantage in some Florida applications: it allows moisture vapor to dry out rather than trap it.

Hurricane Protection: A Florida Priority

After Hurricane Ian struck Southwest Florida in September 2022 as a Category 4 storm, many homeowners discovered a surprising benefit of closed-cell spray foam: it adds structural strength to wall and roof assemblies.

Research from various university wind engineering programs has shown that closed-cell spray foam bonded to structural members can meaningfully increase a wall's resistance to racking forces — the lateral forces that cause walls to fail during high winds. Fiberglass batts provide zero structural contribution. For homeowners in Naples, Fort Myers, and Marco Island — all of which sit in high hurricane risk zones — this is a significant advantage worth serious consideration.

Long-Term Durability and Maintenance

Properly installed spray foam insulation lasts the lifetime of your home — typically 80 years or more. It doesn't sag, settle, or compress over time. It doesn't absorb moisture and lose R-value. It doesn't become a nesting material for rodents, insects, or birds.

Fiberglass batts, by contrast, have a typical useful life of 15–25 years before they begin to compress and lose effectiveness. In Florida's humid environment, that timeline can be even shorter if any moisture infiltrates the wall assembly.

Cost: Spray Foam Is Worth the Investment in Florida

Spray foam insulation costs more upfront than fiberglass — typically 2–4x more per square foot. However, for Florida homeowners, the financial case for spray foam is compelling:

• Energy savings of 30–50% mean most SWFL homeowners recoup the cost in 3–7 years
• No replacement cost for the life of the home (vs. fiberglass every 15–25 years)
• Reduced HVAC maintenance and longer HVAC system lifespan
• Increased home resale value — energy-efficient homes command premiums
• Reduced risk of costly mold remediation

When you factor in lifetime costs rather than just installation costs, spray foam is often the more economical choice for Florida homeowners who plan to stay in their homes for more than 5–7 years.

The Bottom Line for Florida Homeowners

For the vast majority of Naples, Fort Myers, Bonita Springs, and Southwest Florida homeowners, spray foam insulation is the superior choice. The combination of complete air sealing, moisture resistance, hurricane protection, and long-term durability makes it the clear winner in Florida's demanding climate.

The only case where fiberglass might make sense is in tight-budget situations where the upfront cost is the primary constraint. Even then, we typically recommend closed-cell spray foam for at least the attic, where the ROI is highest.