Spray foam vs blown-in insulation in Florida
SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Blown-in insulation is enough for many Florida attics, and it costs less. Spray foam on the roof deck can seal the attic, and Florida's wind-mitigation form credits it, but inspectors raise real questions about hidden roof problems. The right choice depends on your roof, your ducts and your budget.
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SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Last reviewed October 18, 2026 against the cited sources. A guide, not legal, tax or engineering advice.
Updated . Sources
The short answer
Blown-in sits on the attic floor. It costs less, and it is easy to add to or take out.
Spray foam is worth pricing when your air handler or ducts sit in the attic, or when you want a sealed attic. Florida law treats an unvented attic as meeting the energy code under set conditions. These include at least R-20 of air-impermeable insulation, a tight blower-door result, mechanical ventilation and the HVAC equipment inside the sealed space 1.
Ask a roofer and your insurer before you choose foam on the roof deck. The reasons are below.
Side by side
- Cost. PickHVAC lists blown-in fiberglass at 1.60-2.40 USD per sq ft2, open-cell foam at 3.80-4.95 USD per sq ft2 and closed-cell foam at 5.35-6.75 USD per sq ft2. These are national guides.
- Where it goes. Blown-in covers the attic floor. Foam can go on the floor or on the underside of the roof deck.
- R-value per inch. It differs by product. Ask for the installed R-value to be written in your scope, not just the thickness.
- Moisture. A September 2024 FSEC and UCF review found that studies in hot, humid climates saw acceptable wood moisture in unvented attics with foam on the roof sheathing 3. Spikes were rare and short. Some studies saw attic air humidity above 60 percent 3. Open-cell foam was the type studied.
- Roof checks. One home inspector writes that foam on the roof deck makes leaks harder to see, makes repairs messy and costly, and can void a shingle warranty 4. That is one inspector's opinion, and it is not specific to Florida.
- Insurance. Florida's wind-mitigation form lists foam on the underside of the roof deck as a way to qualify for a sealed roof deck, if it is applied at the rafter and deck joints 5. How much discount you get is up to each insurer. Ask your insurer in writing and keep before-and-after photos.
Which homes suit which
- Blown-in suits a dry attic with open floor space, a roof in good shape and a tight budget. It also suits a thin layer that needs topping up.
- Foam suits an attic with ducts or an air handler in it, or a house where you want a sealed attic and your roofer and insurer agree.
- Remove first when old insulation is wet or contaminated. Price guides say wet loose-fill should be removed 6.
- Stop and call a specialist if you suspect asbestos or vermiculite insulation. That is licensed abatement work.
See what each costs in the cost guide. Your attic depth, your ducts and your roof tell you which group your house is in.
National price ranges for attic insulation
| Job | Range | Source |
|---|---|---|
| FSEC: in the Southeast a radiant barrier can reasonably take 8-12 percent off annual cooling costs (worked example: 1,500 sq ft Central Florida house); benefit shrinks with more insulation: at R-30 or better there is very little heat flow left for a barrier to block | 8-12 percent of cooling cost | [16] |
| Blown-in fiberglass, full depth, installed | 1.60-2.40 USD per sq ft | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Blown-in cellulose, full depth, installed | 1.90-2.75 USD per sq ft | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Open-cell spray foam (envelope), installed | 3.80-4.95 USD per sq ft | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Closed-cell spray foam (envelope), installed | 5.35-6.75 USD per sq ft | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Blown-in, typical 1,500 sq ft attic, total | 1875-4125 USD | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Blown-in fiberglass 1.00-2.50 and cellulose 1.20-3.00 per sq ft installed | 1.00-3.00 USD per sq ft | [6]National price guide range, How Much Does Attic Insulation Cost? 2026 Guide, July 2026 |
| Spray foam (open and closed not split) | 1.50-5.00 USD per sq ft | [6]National price guide range, How Much Does Attic Insulation Cost? 2026 Guide, July 2026 |
| Typical 1,500 sq ft attic, total | 2000-4500 USD | [6]National price guide range, How Much Does Attic Insulation Cost? 2026 Guide, July 2026 |
| Typical 2,000 sq ft attic, total | 3000-7000 USD | [6]National price guide range, How Much Does Attic Insulation Cost? 2026 Guide, July 2026 |
| Removing old attic insulation: Angi and HomeAdvisor both list $1 to $1.50 per square foot (Angi also adds air sealing at $250 to $750). | 1.00-1.50 USD per sq ft | [17]National price guide range, How Much Does Attic Insulation Cost? [2026 Data] (Angi), October 2026 |
| Contractor blog: open-cell 1.50-3.50 and closed-cell 2.00-4.75 per sq ft in Florida 2026; typical attic retrofit 1,700-7,500 | 1700-7500 USD | [18]National price guide range, Florida Spray Foam Insulation: Costs, Climate & Building Code Guide (2026), June 2026 |
| Spray foam, 1,500 sq ft at 3.80-6.75 per sq ft (PickHVAC envelope prices); 2,000 sq ft shown in note | 5700-10125 USD | [2]National price guide range, Attic Insulation Cost and Guide 2026 - PICKHVAC, May 2026 |
| Angi: blown-in attic insulation costs $1 to $4 per square foot (table 'Average Cost Per Square Foot in 2026'); national average attic $2,100, most homeowners $1,700 to $2,500.National range from a price guide, not a local quote. | 1-4 USD per sq ft | [17]National price guide range, How Much Does Attic Insulation Cost? [2026 Data] (Angi), October 2026 |
| Angi: spray foam attic insulation costs $2 to $5 per square foot (no open-cell / closed-cell split).National range from a price guide, not a local quote. | 2-5 USD per sq ft | [17]National price guide range, How Much Does Attic Insulation Cost? [2026 Data] (Angi), October 2026 |
| HomeGuide: blown-in insulation costs $0.90 to $2.40 per square foot, or $900 to $3,600 total.National range from a price guide, not a local quote. | 0.90-2.40 USD per sq ft | [19]National price guide range, How Much Does Attic Insulation Cost? (HomeGuide), January 2026 |
| HomeGuide: attic spray foam insulation costs $1.50 to $5.00 per square foot.National range from a price guide, not a local quote. | 1.50-5.00 USD per sq ft | [19]National price guide range, How Much Does Attic Insulation Cost? (HomeGuide), January 2026 |
| HomeAdvisor: removing old attic insulation costs $1 to $1.50 per square foot.National range from a price guide, not a local quote. | 1.00-1.50 USD per sq ft | [20]National price guide range, How Much Does It Cost to Insulate an Attic? (HomeAdvisor), June 2026 |
| Angi: contractors charge between $0.60 and $1 per square foot to install both foil and spray-on radiant barriers.National range from a price guide, not a local quote. | 0.60-1.00 USD per sq ft installed | [21]National price guide range, How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 2026 |
| Angi: professional radiant barrier installation costs between $710 and $2,840 for the project.National range from a price guide, not a local quote. | 710-2840 USD | [21]National price guide range, How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 2026 |
Facts used in this guide
As of October 18, 2026
| Fact | Value | Source |
|---|---|---|
| Current Florida Building Code, Energy Conservation is the 8th Edition (2023), effective December 31, 2023 (based on 2021 IECC) | 8th Edition (2023) | [7] December 31, 2023As of October 19, 2026 |
| Florida Building Code 9th Edition (2026) takes effect December 31, 2026; permit applications on/after that date follow it | 2026-12-31 date | [8] 2026As of October 19, 2026 |
| Florida Building Code 9th Edition (2026) applies to permit applications filed on or after December 31, 2026 | 9th Edition (2026)Takes effect December 31, 2026 | [8] 2026As of October 19, 2026 |
| Prescriptive minimum ceiling insulation, Climate Zone 1, FBC Energy Conservation 8th Ed. Table R402.1.2 | 30 R-value (U-0.035) | [7] December 31, 2023As of October 19, 2026 |
| Prescriptive minimum ceiling insulation, Climate Zone 2 (not South Florida), 8th Ed. | 38 R-value (U-0.030) | [9] 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] 2023 |
| Existing-building alterations: R503.1 says alterations comply with new-construction rules; R503.1.1 exceptions include existing ceiling/wall/floor cavities that are not exposed (and exposed cavities filled with insulation), provided the building's energy use is not increased | text code text | [11] 2023 |
| F.S. 553.9065: unvented attic assemblies insulated with at least R-20 air-impermeable insulation are deemed to meet the energy code if blower door is below 3 ACH50, mechanical ventilation is present, exposed rafters have R-3 where applicable, and HVAC equipment/ducts are inside the envelope | 20 R-value | [1] 2026 (2026 Florida Statutes online edition) |
| Florida HB 803 (signed May 2026, effective July 1, 2026): single-family owners and their contractors do not need a building permit for work valued under $7,500; structural, electrical, plumbing, mechanical and gas work still needs one; projects cannot be split; a written request is required | $7,500 USD | [12] May 8, 2026As of October 19, 2026 |
| Annual mean temperature normal: Miami 77.4F, West Palm Beach 75.8F | 77.4 / 75.8 F | [13] 1991-2020 |
| Atlantic hurricane season runs June 1 to November 30; peak is about September 10 | June 1 - Nov 30 dates | [14] 2026 |
| PNNL Building America guide: roof vents are one of the most common pathways for rainwater entry in storms; IBHS recommends vents certified to FBC TAS 100(A); rain entry is easier to control at soffits than at upper roof vents; unvented attic assemblies may be the best practice in high-wind areas | n/a | [15] December 5, 2022 |
Attic Heat Score
Answer a few quick questions. The score shows how likely your attic is to benefit from more insulation. It is a starting point; a measured depth confirms it.
Start the Attic Heat ScoreSFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
Questions people ask
What is the right insulation for a Florida attic?
There is no single answer. Many attics do well with blown-in brought up to the new-home minimum of R-30 7. Foam fits when ducts sit in the attic or you want a sealed attic. Your attic depth, ducts and roof show which fits yours.
Does spray foam cause roof problems in Florida?
We found no insurer bulletin or state rule that objects to it, and the state's own mitigation form credits it. The worries are real, though. One inspector says foam hides leaks, and the 2024 review saw some high humidity in the studies it covered 3. Ask your roofer and your insurer before you choose it.
Sources
- Florida Statutes 553.9065, unvented attic assemblies, 2026 (ch. 2024-191)
- Attic Insulation Cost and Guide 2026 - PICKHVAC, May 15, 2026
- FSEC/UCF literature review for the Florida Building Commission, September 16, 2024
- ASHI Reporter: Why I don't like spray foaming roof decks, January 31, 2026
- Florida Office of Insurance Regulation, Uniform Mitigation Verification Inspection Form OIR-B1-1802 (Rev. 04/26), 2026-04
- Block Renovation, attic insulation cost guide 2026, 2026
- Florida Building Code, Energy Conservation, 8th Edition (2023), Table R402.1.2, December 31, 2023
- Important Notice: Florida Building Code 9th Edition Code Change (Miami-Dade Permitting and Inspection Center), 2026
- Appendix RD Forms: Residential Building Thermal Envelope Approach (8th Edition FBC Energy Conservation), 2023
- Chapter 3 [RE] General Requirements: 2023 FBC - Energy Conservation, 8th edition | UpCodes, 2023
- Chapter 5 [RE] Existing Buildings: 2023 FBC - Energy Conservation, 8th edition | UpCodes, 2023
- A new Florida law will drop permits for low-cost home projects | WLRN, May 8, 2026
- NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal: Miami Intl Airport, FL, 1991-2020
- Tropical Cyclone Climatology, 2026
- Disaster-Resistant Roof Venting | Building America Solution Center, December 5, 2022
- Radiant Barriers: A Question and Answer Primer (FSEC-EN-15), 2005 (copyright year; revisions undated)
- How Much Does Attic Insulation Cost? [2026 Data] (Angi), October 12, 2026
- Florida Spray Foam Insulation: Costs, Climate & Building Code Guide (2026), June 16, 2026
- How Much Does Attic Insulation Cost? (HomeGuide), January 13, 2026
- How Much Does It Cost to Insulate an Attic? (HomeAdvisor), June 20, 2026
- How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 14, 2026