Fiberglass vs Cellulose Insulation in Florida: Which Is Right for Your Attic?

When homeowners in Boca Raton research blown-in attic insulation, one of the most common questions is: fiberglass or cellulose? Both are legitimate insulation materials with real-world track records. But in South Florida's specific climate conditions, they perform differently — and the differences matter.

What Is Blown-In Fiberglass?

Blown-in fiberglass insulation is made from spun glass fibers. It is inorganic, meaning it contains no organic material that can decompose, absorb moisture, or support biological growth. High-density blown fiberglass — the product Cardinal Insulation installs — is a denser, more stable version of standard loose-fill fiberglass.

What Is Blown-In Cellulose?

Blown-in cellulose is made from recycled paper (typically newsprint) treated with borate fire retardants. It is an eco-friendly option with good initial R-value performance. It is also the most common alternative to fiberglass in the blown-in insulation market.

The Florida Climate Factor

Here is where the comparison gets important for Boca Raton homeowners specifically.

Moisture absorption. Cellulose is organic — it is paper — and it absorbs moisture. In most of the country, this is a manageable issue. In South Florida, where relative humidity regularly exceeds 80% and attic conditions are extreme, moisture absorption is a real concern. Cellulose that absorbs moisture loses R-value, can compact, and in severe cases can create conditions for mold growth.

High-density fiberglass is inorganic. It does not absorb moisture. Its R-value is not affected by humidity. In Florida's climate, this is a significant advantage.

Settling over time. Cellulose settles more than fiberglass over time, particularly in hot, humid conditions. Settling reduces the installed depth and therefore the effective R-value. A cellulose installation that starts at R-38 may be at R-32 or R-30 after several Florida summers.

High-density blown fiberglass holds its depth and R-value for decades. It does not settle under normal conditions.

Pest resistance. Cellulose is treated with borate to resist insects and rodents, but the treatment can diminish over time. Fiberglass is inherently unattractive to pests — there is nothing organic for them to eat or nest in.

Fire performance. Both materials meet fire safety requirements. Cellulose requires chemical treatment (borate) to achieve fire resistance. Fiberglass is naturally non-combustible.

When Cellulose Makes Sense

Cellulose is not a bad product. It has a lower carbon footprint than fiberglass (recycled content), and it performs well in climates with lower humidity. For some applications — particularly in older homes with irregular attic configurations where cellulose's density helps it fill gaps — it can be the right choice.

Cardinal Insulation offers blown-in cellulose for specific situations where it is the appropriate material. We will tell you honestly when that is the case.

Our Standard for Boca Raton Homes

For the vast majority of Boca Raton attics, high-density blown fiberglass is the superior long-term investment. It handles Florida's humidity better, holds its R-value longer, and does not require chemical treatments to perform.

We install high-density blown fiberglass to R-38 certified depth on every standard job. We start with a complete air seal — which makes the insulation actually work — and document everything with photos and R-value certification.

Call Cardinal Insulation at (561) 654-7698 or email [email protected] for a free attic assessment. We serve all of Boca Raton and Palm Beach County, 7 days a week.

Cardinal Insulation — 4263 NW 1st Ave, Boca Raton, FL 33431