Blown-In Fiberglass vs Cellulose: Which Is Better for Florida?

When Florida homeowners research attic insulation, the choice almost always comes down to two blown-in materials: fiberglass and cellulose. Both can hit the R-38 target recommended for warm climates, but they behave very differently under Florida's relentless humidity. This comparison explains why InsulX Insulation Services installs blown-in fiberglass on virtually every project.

Blown-in fiberglass

Blown-in fiberglass is spun from molten glass into millions of tiny fibers. It is non-combustible by nature — no chemical fire retardants needed — and it does not absorb water. In a Florida attic that regularly hits 130°F with high ambient humidity, that matters: fiberglass stays light, holds its installed R-value for decades, and does not settle into a compressed mat the way denser materials can. It also allows air to move through the attic's ventilation channels, which keeps moisture from being trapped against the roof deck.

Cellulose insulation

Cellulose is made from recycled paper, treated with borates for fire and pest resistance. It installs dense and fills gaps well, which makes it attractive for air sealing. The trade-off in Florida is moisture: cellulose can absorb and hold humidity, and when it gets wet it can compact, lose R-value, and create conditions favorable to mold. In a climate where attic ventilation is already a challenge, a material that holds water is a long-term risk.

The verdict for Florida

For Florida homes, blown-in fiberglass is the safer, more durable choice. It resists moisture, never loses its fire resistance, maintains R-value over time, and works with — not against — attic ventilation. Pair it with professional air sealing at penetrations and top plates, and you get the airtight performance cellulose promises without the humidity downside. Ready to compare quotes? Talk to our team or use the instant quote tool on the home page.