Cardinal Insulation, 4263 NW 1st Ave, Boca Raton, FL 33431. Blown-in insulation is the first service. Cellulose is one of the two products. Fiberglass is the other. They are not the same R-value, and a quote that prints one band for both is hiding the choice.
The number
New cellulose is about R-3.6 per inch. Cellulose already in the attic is counted at about R-3.2. From a bare ceiling, R-38 is about 10.5 inches. Over four inches of settled fiberglass, about R-9, the gap is about 8 inches of new cellulose. Fiberglass for that same gap is about 12 inches, because new fiberglass is about R-2.5 per inch and settled fiberglass is about R-2.2.
A cellulose bag covers fewer square-foot-inches than a fiberglass bag, about 220 against about 640, because the fiber is packed denser. Bag count is the second check on the depth. It is not a number we invent after the truck is empty.
When we use it
We blow cellulose when the ceiling can carry it and the attic is a match: a sound drywall lid, a span that is not already complaining, and no reason to keep the layer as light as fiberglass. We do not switch to cellulose because the R-per-inch looks better on a proposal. An old plaster ceiling, a long span, or a lid that already holds a thick layer stays with the lighter product.
Dry cellulose that is already there gets counted and topped. Wet cellulose, or cellulose full of nests, comes out first. That removal is its own price. Cellulose does not air-seal the ceiling. The holes are closed before the hose, the same as fiberglass. The install page is blown-in insulation. The Boca neighborhoods are on blown-in insulation in Boca Raton.
Florida's zone 1 ceiling minimum is R-30. We install R-38 and check the inches. Cellulose is not R-49, and it is not a reason to close the soffit vents.