Measured against the Florida code
The attic numbers, not a brochure
The 2023 Florida Building Code, Energy Conservation, Table R402.1.2 sets a climate zone 1 ceiling at R-30 and a climate zone 2 ceiling at R-38. Cardinal installs R-38 and checks the inches. A Florida page that lists R-49 to R-60, or R-3.2 to R-3.8 per inch for both fiberglass and cellulose, is using a different book. Table R402.4.1.1 says air-permeable insulation shall not be used as the air seal.
Quotes are prepared by Russell Y, a building scientist, BPI certified, and certified to perform blower door testing. When the door is run, the result is air changes per hour at 50 pascals, the method in R402.4.1.2. That section limits new houses in climate zones 1 and 2 to 7 ACH50. An insulation job on an existing house is not automatically that test. We report the number only when we measured it.
Insulation numbers Cardinal uses against the Florida code| Item | Number | What it means |
|---|
| Zone 1 ceiling, Florida code | R-30 minimum | Palm Beach and Broward |
|---|
| Zone 2 ceiling, Florida code | R-38 minimum | Not R-49 and not R-60 |
|---|
| What Cardinal installs | R-38, depth checked | Above the zone 1 floor |
|---|
| New blown fiberglass | About R-2.5 per inch | Not R-3.2 to R-3.8 |
|---|
| Settled fiberglass | About R-2.2 per inch | 4 inches is about R-9 |
|---|
| New cellulose | About R-3.6 per inch | Denser. Still not an air seal |
|---|
| Open-cell foam | About R-3.6 per inch | A roof-deck product |
|---|
| Closed-cell foam | About R-6.5 per inch | 2 inches is about R-13 |
|---|
The attics on this page
Greenacres sits between Lake Worth and Wellington. The houses are mostly single-story ranches. The original batts have slumped toward the middle of the span and pulled off the plates, which is where the soffit air comes in.
A ranch here is often one day once the hatch, the bath fan, and the top plates are sealed. The bath fan has to leave the building. A fan dumped into the attic is a moisture problem on the deck, and we do not bury it. There is no shop in the city.
Foam is uncommon unless someone enclosed a patio or added a bonus room. Those are a different assembly from the ranch attic. The ranch stays a blown-in floor. The phone is (561) 654-7698.
The code in Greenacres
Greenacres is in Palm Beach County. Table R301.1 of the 2023 Florida Building Code, Energy Conservation, lists Palm Beach County as climate zone 1A. Table R402.1.2 sets the zone 1 ceiling minimum at R-30. Greenacres does not publish its own attic R-value. The city enforces the Florida Building Code.
Palm Beach County is not in the High-Velocity Hurricane Zone. That zone is only Miami-Dade and Broward. Parts of the Palm Beach coast are still a wind-borne debris region, which is an opening-protection rule from the wind map, not an insulation number. Section R806.2 of the 2023 Florida Building Code, Residential, sets the net free vent area at 1/150 of the attic. The exception is 1/300 only when 40 to 50 percent of that area is within 3 feet of the ridge and the rest is in the bottom third. Insulation cannot close the soffit. R806.3 requires at least 1 inch at the eave vent.
The county zone is Table R301.1. The Boca Raton worked example, including the vent math, is the building code page. Cardinal still installs a vented attic to R-38 and checks the depth.
Blown-in insulation, the full pageResidential insulationWhich insulation belongs in a Florida houseWho writes the quoteHow a South Florida attic actually works