Attic Cost and Gap Calculator
SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
This calculator compares your attic's R-value, typed or worked out from a depth in inches, with the Florida code minimum for new ceilings. It prices the gap with national guide ranges, not a quote, and checks the FPL ceiling insulation rebate conditions one by one. An installer has to measure your attic before anyone can price it.
Last reviewed October 18, 2026 against the cited sources.
Updated . Sources
Your attic
Where the R-value range comes from, source by source:
The gap is measured against the Florida code minimum for new construction in this climate zone. Use it as a yardstick, not as a ruling on your existing insulation. An installer has to measure the real depth.
Cost range by insulation type
For square feet. National price guide range, not a quote. Our arithmetic: your area times each type's low and high rate in the table below, from the source and date listed there. The guide rates are for a full-depth job; a bid for a smaller top-up can differ.
FPL ceiling insulation rebate check
Still to do before any rebate:
This check uses only the conditions listed under "The rules behind the check" below, and your own answers. FPL and the contractor confirm eligibility; this page does not decide it.
SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Attic Cost and Gap Calculator
Enter your attic size in square feet. Then give the R-value of the insulation you have now, or pick the material and enter its depth in inches and we work out a range. Leave both blank if you do not know either: you still get the cost ranges and a list of what the rebate check is missing.
SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Before you use the result
- The code minimum applies to new construction. It is a yardstick for your attic, not a rule that your existing attic must meet it.
- A depth gives a range of R-values, not one number, because the sources give ranges. Closed-cell spray foam is the widest case: the Building America spray foam guide lists 6.1 R-value per inch1 for typical aged foam, while the DOE insulation guide lists 7-9 R-value per inch2 for medium-density foam. The calculator uses the range that spans both and lists each source in the result.
- Spray foam is priced on the roof deck in the guides we read, so a real bid on your attic floor area can run higher than the range shown.
How the numbers are worked out
The gap is the Florida code minimum for ceiling insulation in this climate zone minus your R-value. A depth in inches becomes an R-value range: the depth times the material's R-value per inch, using the lowest and highest figure the sources give. The gap and the rebate R-value test are then read across that range. The cost ranges multiply your area by per-square-foot ranges from national price guides, each with its source and date. The rebate check reads the FPL program standards condition by condition and uses your answers, and FPL confirms eligibility. Nothing here is a quote, a savings claim or a promise of a rebate.
Gap = the code minimum minus your R-value, never below zero. Cost = your area times each type's low and high rate, plus the removal rate if you tick it. Our arithmetic from the rates below.
Depth: if you leave the R-value blank and enter a depth and a material instead, the R-value is your depth times the material's R-value per inch, as a range, rounded to whole R-values. The range spans the sources listed in the next table, and the gap is read across that range. If you type an R-value too, the typed R-value is used. Our arithmetic from the per-inch values below.
R-value per inch, by material and source
Each source gives its own figure, and the sources do not always agree. The range the calculator uses for a material runs from the lowest to the highest figure in its rows. These are published, approximate values for general comparison.
| Material | Source | Per inch in the source | Cite |
|---|---|---|---|
| Blown-in fiberglass | DOE and Building America insulation guide, May 2012 | 2.2-2.7 | [2] |
| Blown-in fiberglass | Owens Corning AttiCat data sheet (our arithmetic), May 2026 | 2.7-2.9 | [3] |
| Blown-in fiberglass | Range used | 2.2 to 2.9 | our arithmetic |
| Blown-in cellulose | DOE and Building America insulation guide, May 2012 | 2.9-3.4 | [2] |
| Blown-in cellulose | Greenfiber dry attic chart, settled depth (our arithmetic), September 2024 | 3.4-3.5 | [4] |
| Blown-in cellulose | Range used | 2.9 to 3.5 | our arithmetic |
| Fiberglass batts | DOE and Building America insulation guide, standard density, May 2012 | 2.9-3.8 (standard); 3.7-4.3 (high density) | [2] |
| Fiberglass batts | Owens Corning EcoTouch batt sheet (our arithmetic), July 2018 | 3.0-3.5 | [5] |
| Fiberglass batts | Range used | 2.9 to 3.8 | our arithmetic |
| Open-cell spray foam | DOE and Building America insulation guide, May 2012 | 3.5-3.8 | [2] |
| Open-cell spray foam | Building America spray foam guide, aged, April 2009 | 3.6 | [1] |
| Open-cell spray foam | Natural-Therm data sheet (manufacturer), August 2016 | 3.7 | [6] |
| Open-cell spray foam | Range used | 3.5 to 3.8 | our arithmetic |
| Closed-cell spray foam | Building America spray foam guide, aged, April 2009 | 6.1 | [1] |
| Closed-cell spray foam | DOE and Building America insulation guide, May 2012 | 7-9 | [2] |
| Closed-cell spray foam | Range used | 6.1 to 9 | our arithmetic |
The rules behind the check
Each line is a sourced fact with its source date. The check applies them as written.
- Prescriptive minimum ceiling insulation, Climate Zone 1, FBC Energy Conservation 8th Ed. Table R402.1.230 R-value (U-0.035)[9]Source date: December 31, 2023
- Miami-Dade, Broward and Palm Beach counties are all Climate Zone 1A in the FBC Energy Conservation 8th Edition (Palm Beach moved from Zone 2 to Zone 1)Zone 1 climate zone[10]Source date: 2023
- FPL residential ceiling insulation rebate220 USD per installation[11]Source date: 2025-09-01 (program standards effective date)
- Eligibility: active FPL residential account, whole-house central electric AC and heating, verified existing ceiling R-value below R-8, all attic spaces accessible, hired PIC, once per home every 20 yearsbelow R-8 R-value[11]Source date: September 1, 2025
- Not eligible: additions or renovations, inaccessible attics, flat roofs, insulation over unfinished drop ceilings; material may be blown-in, batt or spray foam and must be new[11]Source date: September 1, 2025
- FPL ceiling insulation rebate is current in October 2026 with no announced end dateopen status[12]Source date: October 18, 2026
Find your numbers (works without a script)
| Current R-value | Gap | Rebate R-value test |
|---|---|---|
| R-0 | Gap to the code minimum: R-30 | met |
| R-7 | Gap to the code minimum: R-23 | met |
| R-8 | Gap to the code minimum: R-22 | not met |
| R-11 | Gap to the code minimum: R-19 | not met |
| R-19 | Gap to the code minimum: R-11 | not met |
| R-30 | No gap: at or above the code minimum of R-30 | not met |
| Depth | Blown-in fiberglass | Blown-in cellulose | Fiberglass batts | Open-cell spray foam | Closed-cell spray foam |
|---|---|---|---|---|---|
| 3 in | R-7 to R-9 | R-9 to R-11 | R-9 to R-11 | R-11 | R-18 to R-27 |
| 6 in | R-13 to R-17 | R-17 to R-21 | R-17 to R-23 | R-21 to R-23 | R-37 to R-54 |
| 9 in | R-20 to R-26 | R-26 to R-32 | R-26 to R-34 | R-32 to R-34 | R-55 to R-81 |
| 12 in | R-26 to R-35 | R-35 to R-42 | R-35 to R-46 | R-42 to R-46 | R-73 to R-108 |
| Attic size | Blown-in fiberglass, full depth | Blown-in cellulose, full depth | Open-cell spray foam | Closed-cell spray foam |
|---|---|---|---|---|
| Smaller attic (1000 sq ft) | $1,600 to $2,400 | $1,900 to $2,750 | $3,800 to $4,950 | $5,350 to $6,750 |
| Mid-size attic (1500 sq ft) | $2,400 to $3,600 | $2,850 to $4,125 | $5,700 to $7,425 | $8,025 to $10,125 |
| Larger attic (2000 sq ft) | $3,200 to $4,800 | $3,800 to $5,500 | $7,600 to $9,900 | $10,700 to $13,500 |
What the result leaves out
- Air sealing, repairs and anything found once the attic is open.
- Roof-deck foam prices on a pitched roof, which cover more surface than the attic floor.
- Any local price. Every rate here is a national guide rate.
- Savings. This calculator makes no claim about energy use or payback.
Where to go next
Read the attic insulation price guide for every source and the questions to put to an installer. The code guide explains the minimum and the code edition dates. The Attic Heat Score looks at the signs in your home instead of the numbers.
Sources
- Which Spray Foam Is Right For You? (Building America / U.S. DOE, last update 2009-04-03), April 3, 2009
- Building America Best Practices Series Vol. 12: Energy Renovations-Insulation, Table 3.2 Insulation Materials (U.S. DOE, May 2012), 2012-05
- AttiCat PINK Blown-In Insulation Product Data Sheet (Owens Corning, Pub. 10011273-L, May 2026), 2026-05
- Applegate Stabilized Cellulose Insulation Fact Sheet, Dry Attic Loose-Fill chart (Greenfiber, PDF created 2024-09-04), September 4, 2024
- EcoTouch PINK Fiberglas Insulation Submittal Sheet (Owens Corning, Pub. 10019001-I, July 2018), 2018-07
- Natural-Therm 0.50 PCF Open Cell Spray Foam Technical Data Sheet (manufacturer, PDF created 2016-08), 2016-08
- Attic Insulation Cost and Guide 2026 - PICKHVAC, May 15, 2026
- How Much Does Attic Insulation Cost? [2026 Data] (Angi), October 12, 2026
- 2023 Florida Building Code: Summary of Key Residential Energy Code Requirements (Insulation Institute), December 31, 2023
- Chapter 3 [RE] General Requirements: 2023 FBC - Energy Conservation, 8th edition | UpCodes, 2023
- Residential Ceiling Insulation Program Standards (Florida Power & Light), 2025-09-01 (program standards effective date)
- FPL | Ways to Save | Ceiling Insulation Rebate, October 18, 2026