R6 or R8 Flex duct in attic in Florida (2024)

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The 2010 Florida Building Code, Energy Conservation states R6 in attics. Has this changed? If so, where can it be found in the Florida code books?

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Originally Posted by garmin

The 2010 Florida Building Code, Energy Conservation states R6 in attics. Has this changed? If so, where can it be found in the Florida code books?

Unfortunately, there is some bad information on this site and the internet in regard to mechanical building code in Florida.
I’m a South Florida air conditioning contractor that does approximately 40-60 new construction homes a year, and has been in business for 25 years.
You will see my synopsis at the end of this writing. It will clarify all the codes for you in regard to R-6 or R-8 requirement’s, air handlers in the attic, and duct testing (not blower door testing).

As of July 2017 the code is as follows:

R403.3.1 Insulation (PRESCRIPTIVE).
Supply and return ducts in attics shall be insulated to a minimum of R-8 where 3 inches (76 mm) in diameter and greater and R-6 where less than 3 inches (76 mm) in diameter. Supply and return ducts in other portions of the building shall be insulated to a minimum of R-6 where 3 inches (76 mm) in diameter or greater and R-4.2 where less than 3 inches (76 mm) in diameter.
Exception: Ducts or portions thereof located completely inside the building thermal envelope.

SECTION R405
SIMULATED PERFORMANCE ALTERNATIVE (PERFORMANCE)
R405.2 Mandatory requirements.
Compliance with this section requires that the mandatory provisions identified in Section R401.2 be met. All supply and return ducts not completely inside the building thermal envelope shall be insulated to a minimum of R-6. (This is allowing you to utilize R-6 supply duct work in attics if the “performance method” is utilized for the energy calculations).

Duct Testing:
R403.3.3 Duct testing (Mandatory).
Ducts shall be pressure tested to determine air leakage by one of the following methods:
1. Rough-in test: Total leakage shall be measured with a pressure differential of 0.1 inch w.g. (25 Pa) across the system, including the manufacturer’s air handler enclosure if installed at the time of the test. All registers shall be taped or otherwise sealed during the test.
2. Postconstruction test: Total leakage shall be measured with a pressure differential of 0.1 inch w.g. (25 Pa) across the entire system, including the manufacturer’s air handler enclosure. Registers shall be taped or otherwise sealed during the test.
Exceptions:
1. A duct air leakage test shall not be required where the ducts and air handlers are located entirely within the building thermal envelope.
2. Duct testing is not mandatory for buildings complying by Section 405 of this code.
A written report of the results of the test shall be signed by the party conducting the test and provided to the code official.

AIR HANDLERS IN THE ATTIC:
R403.3.6 Air-handling units.
Air-handling units shall not be installed in the attic when a home is brought into code compliance by Section R402. Air-handling units shall be allowed in attics for compliance by Section R405 only if the following conditions are met:
1.The service panel of the equipment is located within 6 feet (1829 mm) of an attic access.
2.A device is installed to alert the owner or shut down the unit when the condensation drain is not working properly.
3. The attic access opening is of sufficient size to replace the air handler.
4.A notice is posted on the electric service panel indicating to the homeowner that the air handler is located in the attic. Said notice shall be in all capitals, in 16-point type, with the title and first paragraph in bold:
NOTICE TO HOMEOWNER
A PART OF YOUR AIR-CONDITIONING SYSTEM, THE AIR HANDLER, IS LOCATED IN THE ATTIC. FOR PROPER, EFFICIENT AND ECONOMIC OPERATION OF THE AIRCONDITIONING SYSTEM, YOU MUST ENSURE THAT REGULAR MAINTENANCE IS PERFORMED. YOUR AIR-CONDITIONING SYSTEM IS EQUIPPED WITH ONE OR BOTH OF THE FOLLOWING: (1) A DEVICE THAT WILL ALERT YOU WHEN THE CONDENSATION DRAIN IS NOT WORKING PROPERLY OR (2) A DEVICE THAT WILL SHUT DOWN THE SYSTEM WHEN THE CONDENSATION DRAIN IS NOT WORKING. TO LIMIT POTENTIAL DAMAGE TO YOUR HOME, AND TO AVOID DISRUPTION OF SERVICE, IT IS RECOMMENDED THAT YOU ENSURE PROPER WORKING ORDER OF THESE DEVICES BEFORE EACH SEASON OF PEAK OPERATION.

What all this means:
If the energy calculations are performed via the “PERFORMANCE METHOD,” R6 can still be utilized in attic spaces. This all performed by the person/company doing the energy calculations – not head loads. If they do the “PRESCRIPTVE METHOD” you will then be required to utilize R-8 for supply ducts in the attic. In the attic means that they are not utilizing spray foam to make it part of the thermal envelope.
The “PERFORMANCE METHOD” also allows for the air handler to be installed in the attic – as long as the other provisions of the code are met. I.e. within 6’ of the scuttle hole, decking, etc.

Duct testing will only be required when the “PRESCRIPTVE METHOD” is utilized, and the ducts are not within the thermal envelope.

I do not know of any companies or designers that perform Energy calculations that utilize the “PRESCRIPTVE METHOD;” myself and all the companies I know and have bid, are always the “PERFORMANCE METHOD.”
Unfortunately, these codes can be ambiguous. Thus, a lot of contractors and/or inspectors get the codes incorrect.