The Boca Raton attic: the real zone, the real R-value, and the bag count | Cardinal

The unamended International Energy Conservation Code draws a zone 2 line through a lot of Florida and then asks for a colder-climate attic. Florida amends that map. Palm Beach County, including Boca Raton, is climate zone 1A in the 2023 Florida Building Code, Energy Conservation. The residential volume of the same edition took effect December 31, 2023.

Table R402.1.2 sets the zone 1 ceiling minimum at R-30. Zone 2, which Boca is not, uses R-38 as its minimum. The same table allows a ceiling U-factor of 0.035. R-49 and R-60 are what you get when a page copies the national model for a colder place and prints it over a Boca ZIP. Quoting them does not change the bags, and it does not make a zone 1 attic into zone 2 work.

Boca Raton is also not in the High-Velocity Hurricane Zone. That zone is Miami-Dade and Broward. The hurricane line is a wind rule for the structure. It is not an excuse to print a different attic R-value, and it is not a reason to skip the vents.

New blown fiberglass is figured at about R-2.5 per inch. Settled fiberglass already in the attic is about R-2.2. New cellulose is about R-3.6 per inch and heavier. Cellulose already in place is about R-3.2. A chart that gives both products the same band, about R-3.2 to R-3.8 per inch, makes a fiberglass attic look thicker than the ruler will show.

From a bare ceiling, R-30 of new fiberglass is about 12 inches. R-38 is about 15 inches. R-38 of new cellulose is about 10.5 inches. Most Boca attics are not bare. Four inches of dry settled fiberglass is about R-9. The gap from that to R-38 is about 11 to 12 inches of new fiberglass, installed level. Six inches of settled fiberglass is about R-13, and the gap is about 10 inches.

Going past R-38 adds bags. It does not seal an open hatch, and it does not replace the 1 inch of air that Section R806.3 requires at the soffit. A proposal that sells R-49 or R-60 as the Boca code is selling extra thickness and calling it the law.

Every blown-in bag has a coverage chart. The chart is for a stated R-value at a stated thickness and a stated weight. The chart for a colder climate, or for a higher R per inch than the product will settle to, prints a bag count that looks finished while the eave is still thin. The number that matters is the depth in the attic, not the count the salesman wrote from a national chart.

The Florida energy code wants depth markers for blown ceiling insulation, at least one every 300 square feet, marked in inches and facing the opening. An 1,800 square foot attic needs markers you can read from the hatch. A pile at the hatch and a bare eave averages to a lie. Cardinal leaves the markers. The crew checks the depth before they leave.

Settled depth is the other trick. A bag rated at the installed thickness will be shorter after it settles. Using the new R-2.5 number on fill that has been in a Boca attic since the 1980s is how a top-up comes up short. Old fiberglass is figured near R-2.2 per inch. The bag label from the year the house was built is not the measurement.

A planning range for about 1,800 square feet with about 4 inches of settled fiberglass, brought to R-38 in new blown fiberglass, is about $2,100 to $3,350. That range is on this site. It is not a bid. A tight east-side hatch in 33432, a long West Boca run in 33496, removal, and foam move the number.

A table that prices every Boca attic at one dollar per square foot ignores the hatch, the existing depth, and whether the fill is wet. Removal is its own price. Sanitizing, if the deck needs it after contaminated fill is gone, is a second price. The new blow is a third. Folding those into one square-foot number is how the work that mattered gets skipped.

East Boca, 33432 and the shop ZIP 33431, is where a wet plaster lid and a tight hatch show up. 33486 is the low ranch. West of I-95, 33433, 33496, and 33498 are the wide attics: Woodfield, The Hamptons, Boca Falls, Sandalfoot Cove. Dry original batts stay. Wet, moldy, or rodent-packed fill comes out. A condominium with no scuttle is not either job.

A vented attic over a flat ceiling is blown-in. The attic stays hot. The insulation sits on the ceiling of the rooms below. Batts gap around wires and at the eaves. Dry batts that are already there stay and get topped. They are not torn out so a new batt job can be sold.

Spray foam belongs on a roof deck or a bonus room that should be inside the house, and only after the vents over that roof are closed. Two inches of closed-cell foam is about R-13. It is an air seal on a deck, not an attic-floor R-38. Open-cell fills a deep bay. It is not the product for the vented floor. Foam smells while it cures. Blown-in fiberglass and cellulose do not.

We do not seal ducts, install a radiant barrier, encapsulate a crawl space, or insulate a garage door and call it the attic. Those are different jobs. A page that lists all of them on one Boca menu is not describing the work that cools the bedroom. The bedroom ceiling is the air seal, then the blow.

If the insulation is on the floor, the attic stays vented. Section R806.2 sets the minimum net free ventilating area at 1/150 of the attic area. The exception allows 1/300 when 40 to 50 percent of that area is in the upper third, not more than 3 feet below the ridge, and the balance is in the bottom third. An 1,800 square foot ceiling needs 12 square feet at 1/150, or 6 square feet at the exception.

Section R806.3 says the insulation shall not block the free flow of air at the eave. Not less than a 1-inch space is required between the insulation and the roof sheathing. That is the baffle. In 33432 the eave is often short, so the inch is easy to lose. In a West Boca club the eave run is long, so a missed baffle shows up as a hot stripe along the outside wall. Covering the soffit to chase R-49 closes the attic.

Quotes are prepared by Russell Y, a building scientist who is BPI certified and certified to perform blower door testing. A blower door number is reported only when the test is run. An insulation price on an existing Boca house is not that test. Ask to see the BPI card at the estimate.

The listing this page points at is Cardinal Insulation of Boca Raton LLC, 4263 NW 1st Ave, Boca Raton, FL 33431. Call (561) 654-7698. There is no second Boca pin in West Boca or on State Road 7. Delray Beach is a different walk-in, at 955 S Congress Ave, same phone. Jupiter is a different listing, 17628 Brian Way, (754) 253-9607.

The longer neighborhood walk is at https://cardinalinsulation.com/blog/blown-in-insulation-boca-raton-neighborhoods. The removal, attic, and blown-in sequence is at https://cardinalinsulation.com/blog/insulation-removal-attic-and-blown-in-boca-raton. The code page is https://cardinalinsulation.com/boca-raton-building-code.