There’s a particular kind of frustration that comes with an FPL bill that won’t come down no matter what you do. You’ve had the AC serviced, maybe even upgraded the unit, and the house still feels muggy by mid-afternoon. Nine times out of ten, the attic is the problem—not the equipment.

South Florida’s heat is radiant, not just ambient. The sun bakes a dark roof to 160–180°F on a summer afternoon, and that heat radiates downward through the roof deck into an attic that can hold 140–150°F for hours after sunset. If the insulation between that attic and your living space is compressed, undersized, or missing in spots, your AC is fighting a battle it can’t win. Fiberglass batts and blown-in cellulose exist precisely to interrupt that heat path—and when they’re installed correctly to the right R-value, they do it reliably and cost-effectively.

Why Traditional Insulation Still Makes Sense in Broward County

Spray foam dominates contractor marketing right now, and it has legitimate applications—but it’s not the right answer for every job, and it’s certainly not the only answer. Fiberglass and cellulose have been the workhorses of residential insulation in South Florida for good reason: they perform to code, they handle the climate well, and they cost two to four times less per square foot than spray foam alternatives.

The case for traditional insulation in this region comes down to a few practical realities. Florida’s climate is hot-humid, meaning moisture moves from outside to inside for most of the year. Closed-cell spray foam creates a vapor barrier—which is exactly what you want in a cold climate where you’re keeping warm air in. In South Florida, a vapor barrier on the wrong side of a wall assembly can trap moisture and create conditions favorable to mold. Fiberglass and cellulose are vapor-permeable, which means moisture can move through them without accumulating. That’s not a weakness in this climate—it’s appropriate material behavior.

For attic floor insulation in a vented attic, which is the standard configuration in the overwhelming majority of Broward County homes, blown-in insulation is simply the correct tool. It covers the entire attic floor, fills around obstructions, and reaches the corners and edges that batts can’t always get to cleanly.

Fiberglass Batt Installation: The Details That Determine Performance

Fiberglass batt installation looks straightforward from the outside. It isn’t. The performance difference between a correctly installed batt job and a careless one can be 20–30% of the stated R-value, and most homeowners never know because the insulation is hidden inside a wall or above a ceiling.

Compression kills R-value

Fiberglass insulation works by trapping air in a matrix of glass fibers. Compress it, and you reduce the air space, which reduces thermal resistance proportionally. An R-30 batt compressed into a space designed for R-19 doesn’t give you R-30—it gives you something close to R-19, which is what was there before. This happens constantly in attics where batts have been pushed aside for HVAC work and not restored, or where additional batts have been piled on top of existing ones without attention to depth.

Voids

Voids matter more than most people realize. A 1% void in an insulation installation—meaning 1% of the area has no insulation—reduces the effective R-value of the entire assembly by significantly more than 1%, because heat finds the path of least resistance and moves through the gap disproportionately. Around recessed lighting, plumbing penetrations, and attic hatch frames are the common failure points. These get sealed before insulation goes in, not after.

Vapor retarder orientation

Vapor retarder orientation is climate-specific. Faced fiberglass batts have a kraft paper or foil facing that functions as a Class II vapor retarder. In Florida’s climate zones 1 and 2, that facing faces the conditioned space—toward the interior—or unfaced batts are used entirely. Installers trained in northern climates sometimes get this backwards. It’s a small detail that can create a chronic moisture problem inside a wall cavity over years.

Wall cavities

For wall cavities in new construction or open-wall renovations, fiberglass batts sized for 2×4 or 2×6 framing are cut and fitted from sill to top plate, with every cavity filled without voids, folded edges, or gaps around electrical boxes. Done right, it’s meticulous work.

Blown-In Cellulose: The Right Choice for Attic Topping and Retrofit Work

Cellulose insulation is made from recycled paper fiber—typically post-consumer newsprint—treated with borate compounds for fire resistance and pest deterrence. It’s been used in attic applications for decades, and it remains one of the best options for existing Broward County homes for a specific reason: it installs over existing insulation without requiring removal.

Most Fort Lauderdale homes built between 1970 and 2000 have R-11 to R-19 of original insulation in the attic—fiberglass batts laid between joists that have settled and compressed over 30–40 years of South Florida heat cycling. Adding blown-in cellulose on top of that existing layer brings the assembly up to R-30 or R-38 without the cost and disruption of full removal. The existing insulation still contributes its remaining R-value; the blown-in layer adds the rest.

Cellulose has an R-value of approximately R-3.7 per inch. To reach R-38 starting from zero, you need about 10 inches of settled depth—installers target 11–12 inches at installation to account for the 5–8% settling that occurs in the first year. This isn’t a flaw in the material; it’s a known characteristic that a qualified installer accounts for.

Dense-pack cellulose

Dense-pack cellulose is a different application—blown into enclosed wall cavities at 3.0–3.5 lbs per cubic foot rather than the 1.5–1.8 lbs used for open attic fill. At that density, the material doesn’t settle, and it provides meaningful resistance to air movement through the cavity. For older Fort Lauderdale homes with uninsulated wood-frame walls, dense-pack through drilled holes in the exterior or interior is often the only retrofit option short of removing wall finishes entirely.