Is a radiant barrier worth it in Miami?

SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.

A radiant barrier can help a Miami attic, but it helps less the more insulation you already have. FSEC puts the Southeast cooling-cost gain at 8 to 12 percent a year ¹. Check your insulation depth first.

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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 October 18, 2026. Sources

Radiant barrier in Miami: local facts

Verified facts only. Each one links to its source and shows the source's date.
Fact	Value	Source
Annual cooling degree days (base 65F), Miami Intl Airport (USW00012839), 1991-2020 normal; cooling load is what a radiant barrier acts on	4,656 CDD	[7] 1991-2020
Average days per year with a high of 90F or more, Miami Intl Airport (USW00012839), 1991-2020 normal	91.4 days/year	[7] 1991-2020
Cooling degree days June through September (sum of monthly normals), Miami Intl Airport (USW00012839), 1991-2020	2,258.2 CDD	[8] 1991-2020

Miami's housing and your roof

Miami has some of the oldest housing we cover. The median unit was built in 1979², and 50.8 percent² of units date to 1979 or earlier.

Florida's statewide ceiling rule began with homes permitted after March 15, 1979: R-19 R-value³. Homes permitted before that date had no such rule (our inference). A thin attic is possible in an older home. Age is a clue, not proof.

Few Miami units are detached houses: 22.4 percent². Many homes sit under a shared roof. Foil is fixed under the roof deck, so ask who controls the roof before you plan anything.

Older ZIP areas worth knowing

Some parts of the city skew much older. In ZIP area 33165, 81.1 percent⁴ of units date to 1979 or earlier, and 74.9 percent⁴ are detached houses. In ZIP area 33135 the median build year is 1960⁵.

Farther south, ZIP area 33186 looks different, with a median build year of 1986⁶. Only 28.3 percent⁶ of its units date to 1979 or earlier.

ZIP areas are Census approximations and can spill past the city line. Use them as a guide for where to look first.

What the Miami sun does to a roof

These are NOAA normals for Miami International Airport, not the city itself. Cooling degree days count how much hot weather a year brings.

Cooling degree days a year (1991-2020 normals): 4,656 CDD⁷.
Days a year at 90F or higher: 91.4 days/year⁷.
June to September alone: 2,258.2 CDD⁸ (summed from the monthly normals, our arithmetic).

Winter heating is almost nothing: 103.6 HDD⁷ a year. So foil has one job here, and that is cutting summer heat from the roof.

Is foil the right first move?

As of October 18, 2026

New Miami homes must reach a ceiling minimum of 30 R-value⁹. Treat that as a yardstick for your attic, not a legal demand on an older home.

FSEC says the gain from foil shrinks as insulation rises, and at R-30 or better there is very little heat flow left to block ¹. An attic near that level is a poor target.

If your layer is thin, you can add foil or add more blown-in. Foil only reflects heat. Blown-in adds R-value. Ask for both priced.

FSEC also warns that foil lying flat on insulation can trap moisture ¹. Ask the installer where the foil will go.

Permit, condo and association questions

As of October 18, 2026

We found no City of Miami page that says whether a radiant barrier job needs a permit. Call the building department and ask before you hire anyone.

In a condo or townhouse, the roof is often shared. Get your association's written yes first.

What it costs

No credible recent price for radiant barrier in South Florida turned up, so none is printed here. Ask every bidder for a price per square foot, the area covered and the foil type, all in writing.

Next step

Want to know if your attic is a candidate? Start with the Attic Heat Score.

National price ranges for radiant barrier

These are national ranges from the cited sources, not local quotes. Ranges are labeled with their source, or marked our arithmetic. Your price depends on the job.
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	[10]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	[10]National price guide range, How Much Does a Radiant Barrier Cost to Install? [2026 Data] (Angi), October 2026

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 Score

SFL Attic is a guide run by Terragroupe, LLC. We do not install anything and we are not booking jobs yet.

More attic work in Miami

Questions people ask

Is the FSEC number a Miami number?

No. The worked example behind the 8 to 12 percent figure is a 1,500 square foot Central Florida house ¹, and it is a planning estimate. We have not verified a Miami-only figure.

Can I add foil and insulation together?

Yes. They do different jobs: foil reflects heat and insulation slows it. Because the gain from foil falls as insulation rises, get one price for both and one for insulation alone.

I rent a Miami condo. Does any of this apply to me?

Only if your unit has its own attic space. If the roof is shared, you do not control it. Ask your landlord or association first.