Radiant barrier: turn roof heat back before it reaches your attic
SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.
A radiant barrier is a reflective foil layer in the attic that turns roof heat back toward the roof. FSEC's planning estimate for the Southeast is 8-12 percent of cooling cost1, and the gain shrinks as you add insulation 1. It helps most when attic insulation is thin.
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
What you get
You get less radiant heat falling from the hot underside of the roof onto your insulation and ducts. That can help the rooms below, mostly when the attic insulation is thin.
- The estimate. FSEC's planning estimate for the Southeast is 8-12 percent of cooling cost1 1. It is not a promise.
- The limit. FSEC's worked example is a 1,500 square foot Central Florida house, not a South Florida home 1. We have no South Florida figure we can verify.
- Who it suits. A thin layer of insulation, a sunny roof and a roof you control.
- Who should skip it. An attic that already has deep insulation.
What a radiant barrier is
Heat reaches your attic floor by touch, by moving air and by radiation. A radiant barrier works on radiant heat, the kind you feel off a hot surface. Insulation slows the other kinds.
A radiant barrier is thin metal foil, often aluminum, on paper or plastic. It reflects radiant heat instead of passing it on. The shiny side has to face open air to work. FSEC warns of condensation if foil lies directly on insulation 1.
On a sunny South Florida day, the underside of the roof gets very hot. Foil in the attic turns some of that heat back toward the roof. It does not stop heat that moves by touch or by air.
Types and where the foil goes
- Under the roof deck. Foil sheets are fixed to the underside of the rafters, or the roof sheathing comes foil-faced. This is the usual place.
- On the attic floor. Some installers lay foil across the attic floor. That puts foil close to the insulation, which is where FSEC warns about condensation 1. Ask where the foil will go and why.
- Sprayed-on coatings. Reflective coatings can go on the underside of the roof deck. Ask for the product data sheet and what the maker's claims are based on.
How to choose
- Thin layer of insulation. Price more insulation first, or foil and insulation together. See blown-in insulation.
- Already deep insulation. Foil is probably a weak first move. FSEC says the gain shrinks as insulation rises, and at R-30 or better little heat flow is left to block 1.
- Planning spray foam on the roof deck. Foam seals the attic by itself. Ask the installer whether foil adds anything to that. See spray foam.
- Ducts or an air handler in the attic. Ask the installer to show how that changes the case for foil in your attic.
- A roof that leaks or is near the end of its life. Fix or replace the roof first. Foil fixed to the deck is hard to move later.
- A condo or townhouse. The roof may be shared. Ask your association first.
Florida rules and rebates
South Florida cools far more than it heats, according to NOAA's 1991 to 2020 normals for the Miami airport 2. That is why attic heat is the target here.
New homes in Miami-Dade, Broward and Palm Beach counties need at least R-30 in the ceiling under the 2023 Florida energy code 3. We found no state rule that asks for a radiant barrier.
FPL's ceiling insulation rebate lists blown-in, batt and spray foam as eligible materials 4. Foil is not on that list, so do not count on the rebate for a foil-only job.
A Florida law lets some owners skip a permit on work under $7,500, with a written request 5. Each building department decides how that applies. Ask yours.
How the job goes, step by step
- Look. The installer checks the roof deck for leaks, the rafters and the insulation depth. If the layer is thin, they raise that first.
- Plan the airflow. Foil must not block soffit or ridge vents. The installer marks where air needs to flow.
- Fix the foil. In the usual job, sheets are stapled to the underside of the rafters, shiny side facing open air.
- Check. The installer looks for gaps and tears, and takes photos.
- Paperwork. You get the foil type, where it went and the area covered, in writing.
Attics get very hot in summer. Ask when the work is scheduled and how the installer handles the heat.
What changes the price
Angi lists a radiant barrier at 0.60-1.00 USD per sq ft installed6 and a whole-attic job at 710-2840 USD6. These are national prices, not Florida quotes. Here is how to read a bid.
Ask every bidder for the price per square foot, the area covered, the foil type and where it goes. Then compare bids line by line. What moves a price: roof shape, with its hips and valleys, attic height and access, the foil product, and whether insulation is added in the same visit.
If insulation is part of the job, the cost guide shows national prices for that part.
What is in writing, and the workmanship term
Your written scope should name the foil product and the data sheet, show where it goes, and state the area covered. It should say how the vents stay clear and what the price includes.
Ask for the workmanship term: how long the installer fixes problems with the work. The foil maker may have its own warranty, and it is separate. We will publish the installer's workmanship term here once an installer signs.
How to size up your attic
- Take the Attic Heat Score. Answer a few questions about your home. You get a score and the reasons behind it. It is a starting point, and the Attic Heat Score page shows what it is based on.
- Know what a good check covers. A good attic check records the type of insulation, its depth in inches and photos of problem spots. Use that list when you talk to any installer.
- Ask for a written price. Ask for the scope, the product, the installed R-value and the price in writing. Nothing should start until you say yes.
- Compare and decide. Use the cost guide to compare quotes. If your attic already has enough insulation, you may not need work.
- See the finished job. Ask for photos and a depth reading after the work, so you can see the result.
What we don't handle
These jobs are outside what SFL Attic can help with. If your project includes one of them, we can't take the job.
- roof
- retaining wall
- slab repair
- structural
- electrical
- drain
- mold
- waterproofing
- elevated deck
- balcony
What this site gives you now
This guide is built to remove guesswork, so you can decide from a straight answer with no pressure.
- A way to size up your attic
The Attic Heat Score shows how likely new insulation is to help. Then find the type of insulation, how deep it is and what needs fixing first. - Prices you can compare
Price ranges come from named national guides, each with its source. Ask any installer for the scope, the product and the price in writing. Nothing should start until you say yes. - The right product for your house
Blown-in when it is enough. Spray foam only when it fits your roof and your budget. - A photo habit
Take photos of the attic before and after any work, with a ruler for depth, so you can see the result. - The rebate rules
FPL pays a rebate only when your existing attic insulation is thin. The cost guide explains the rules, so you can see whether you may qualify. - What to ask for in writing
Ask any installer to put the workmanship term in your written scope: what it covers and how long it lasts. We will publish an installer's term on this site if one signs.
This site is free to read. It sells no work and takes no payment. If your attic does not need work, the guides and the score will say so. Any work is agreed in writing between you and the installer who does it.
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.
National price ranges for radiant barrier
| Job | Range | Source |
|---|---|---|
| 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 | [6]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 | [6]National price guide range, How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 2026 |
Radiant barrier in South Florida: cities
Other services
Illustration Blown-in attic insulation
Loose fill blown across the attic floor. The usual fix for a thin layer in a dry, open attic.
Illustration Spray foam attic insulation
Foam on the roof deck that seals the attic. It costs more and fits homes with ducts in the attic.
Attic insulation removal
Takes out wet, soiled or old insulation so new insulation starts on a clean floor.
Guides
Evidence: the facts and sources behind this page
Radiant barrier: facts behind this page
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) | [3] 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 | [7] 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 | [7] 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) | [3] 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) | [8] 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 | [9] 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 | [10] 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 | [11] 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 | [5] May 8, 2026As of October 19, 2026 |
| Annual mean temperature normal: Miami 77.4F, West Palm Beach 75.8F | 77.4 / 75.8 F | [2] 1991-2020 |
| Atlantic hurricane season runs June 1 to November 30; peak is about September 10 | June 1 - Nov 30 dates | [12] 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 | [13] December 5, 2022 |
Sources
- Radiant Barriers: A Question and Answer Primer (FSEC-EN-15), 2005 (copyright year; revisions undated)
- NOAA NCEI climate normals 1991-2020 (annual station file), 1991-2020
- Florida Building Code, Energy Conservation, 8th Edition (2023), Table R402.1.2, December 31, 2023
- FPL residential ceiling insulation program standards, September 1, 2025
- WLRN: a new Florida law will drop permits for low-cost home projects, May 8, 2026
- How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 14, 2026
- 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
- Online Sunshine, Florida Statutes: s. 553.9065, 2026 (2026 Florida Statutes online edition)
- Tropical Cyclone Climatology, 2026
- Disaster-Resistant Roof Venting | Building America Solution Center, December 5, 2022
Questions people ask
Is a radiant barrier worth it in Florida?
It can be, when attic insulation is thin and the roof gets full sun. FSEC's planning estimate for the Southeast is 8-12 percent of cooling cost1 1. The gain shrinks as you add insulation, so check your insulation depth first.
Does a radiant barrier replace insulation?
No. Foil reflects radiant heat. Insulation slows other heat flow. They do different jobs. If your layer is thin, price more insulation too. See blown-in insulation.
Will it help if my attic already has deep insulation?
Probably very little. FSEC says that at R-30 or better there is little heat flow left for a barrier to block 1.
Can foil cause condensation?
FSEC warns of condensation if foil lies directly on insulation 1. Ask where the foil goes and how air reaches its shiny side.
Does the FPL rebate cover a radiant barrier?
We do not think so. FPL lists blown-in, batt and spray foam as eligible materials 4. Foil is not on that list. Ask FPL before you hire anyone.
Is the FSEC number a South Florida number?
No. The worked example behind the figure is a 1,500 square foot Central Florida house 1, and it is a planning estimate. We have not verified a South Florida figure.