The 2026 Florida Building Code, Energy Conservation is bringing some of the most consequential changes to residential energy compliance that Florida builders, HVAC contractors, energy raters, and project teams have seen in recent code cycles. The 9th Edition (2026) Florida Building Code is scheduled to take effect December 31, 2026, and projects subject to the new edition will need to account for substantially different requirements in several areas of residential energy compliance.

Two changes deserve particular attention for builders using Florida’s R405 Simulated Performance Alternative. First, the maximum allowable performance e-Ratio is being reduced from 0.95 to 0.85. Second, the exception that allowed projects complying through R405 to avoid duct leakage testing is being removed. Florida DBPR identifies both as significant residential changes in the new code.

From my experience working with residential energy-code compliance in Florida, these are not minor paperwork changes. R405 performance compliance is extremely common in the residential construction we encounter, which means changes to that pathway can affect everything from energy calculations and equipment selections to field testing, scheduling, subcontractor coordination, and final inspections.

Builders preparing projects that may fall under the 2026 Florida Building Code can contact Stellar Building Performance to discuss energy-code testing, HERS services, and compliance planning before these requirements reach the field.

When Does the 2026 Florida Building Code Take Effect?

The 9th Edition (2026) Florida Building Code is scheduled to take effect December 31, 2026. Florida updates its Building Code on a three-year cycle, and the 2026 edition incorporates the existing 8th Edition (2023) Florida code as its base along with Florida Building Commission-approved modifications developed from the 2024 International Codes and proposals considered during Florida’s 2026 code-change cycle.

At this point, builders should not treat these changes as merely conceptual proposals. DBPR has published its official significant-provision-change material for the 9th Edition, and as of September 2026 the Florida Building Commission and Energy Technical Advisory Committee are already reviewing compliance-software submissions for the new Energy Conservation code.

That makes the remaining months of 2026 an important transition period. Builders with standard plans, specifications, HVAC designs, or energy packages that have worked consistently under the 2023 code should not automatically assume those same combinations will work unchanged under the 2026 edition.

If you build repeatedly from prototype plans, now is the time to start reviewing those specifications against the 2026 requirements rather than discovering problems during permitting or closeout.

The Biggest Change for Many Florida Builders: Duct Leakage Testing

One of the most significant changes in the 2026 Florida energy code occurs in Section R403.3.3.

Under the current 2023 Florida Building Code, duct leakage testing is addressed as a mandatory provision, but an exception has allowed projects complying through Section R405, the Simulated Performance Alternative, to avoid the field duct leakage test.

That exception is being removed.

Florida DBPR’s official 2026 change summary states that the duct-testing exception for R405 performance compliance has been eliminated. Under the new code, ducts generally must be leakage tested unless the ducts and air handlers qualify for the remaining exception by being located entirely within the building thermal envelope. In realistic terms, unless your HVAC system is entirely within a spray foamed attic, duct leakage testing will be required for your project.

Why this is such a substantial change

This distinction matters because simply saying “Florida requires duct leakage testing” doesn’t tell the whole story of how residential compliance has worked in practice.

Duct testing has existed in the code for years. But because so many Florida projects use the R405 performance path, the R405 exception has allowed a large portion of residential construction to proceed without actually completing a field duct leakage test.

The 2026 code changes that dynamic.

Choosing the performance path will no longer, by itself, provide a way around duct leakage testing.

For builders accustomed to completing a blower door test near final inspection without scheduling a corresponding duct test, this may represent an entirely new field-verification step.

What Does a Duct Leakage Test Measure?

A duct leakage test measures how much air escapes from the HVAC duct system under a controlled pressure difference. The duct system is temporarily sealed at the registers and grilles, then specialized testing equipment is used to pressurize or depressurize the system and quantify leakage.

This is different from a blower door test.

A blower door test measures leakage through the building enclosure. A duct leakage test evaluates leakage associated with the HVAC air-distribution system. A house can perform well on one test and poorly on the other because they are evaluating different parts of the building. Blower Door testing will include the duct leakage in its total, but duct leakage testing is isolating the system to measure its leakage specifically.

Under the 2026 code, builders who previously needed only a blower door test because of their chosen compliance path will now need to plan for both tests unless they meet the encapsulation exclusion.

That affects more than the inspection checklist. It affects when the test can be performed, what portions of the HVAC system need to be complete, who needs to coordinate access, and what happens if leakage exceeds the applicable project limit.

Stellar Building Performance provides both blower door and duct leakage testing throughout Brevard, Indian River, St. Lucie, and Okeechobee counties, allowing builders to coordinate required field testing through one local testing partner. See some of our project updates to see how we help builders, contractors, developers, and homeowners near you.

The Remaining Exception: Ducts Inside the Thermal Envelope

There is an important nuance here.

The 2026 code is not simply saying that every duct system in every house must be tested without exception.

The remaining exception in R403.3.3 applies where the ducts and air handlers are located entirely within the building thermal envelope and the requirements of that exception are satisfied. Florida DBPR specifically notes this remaining exception in its explanation of the 2026 change.

This can be particularly relevant to certain spray-foamed roof assemblies and other designs where the HVAC system is genuinely contained within conditioned space.

The important distinction is that R405 itself is no longer the exemption.

That means the physical configuration of the building and HVAC system becomes important when determining whether the remaining exception applies. Builders should not assume that selecting the performance compliance path automatically eliminates duct testing once the 2026 code takes effect.

Rough-In Testing May Become Much More Valuable

This change may also make rough-in duct leakage testing considerably more attractive to builders, and, at the very least for the transitionary period, that is what I would recommend.

Waiting until the end of construction to discover significant duct leakage can create a difficult repair situation. Drywall may already be installed, chases may be closed, boots may be finished, and portions of the duct system that were easily accessible during rough construction may now be concealed.

Testing earlier can give the project team an opportunity to identify leakage while repairs are still relatively accessible.

When needed, we can also use duct smoke testing as a separate diagnostic service to help visually locate leakage points after a problem is identified, and that is why we recommend rough testing. If we test at rough, we can verify the home is on target to pass energy code requirements, and if it isn’t we have a few options:

• Smoke test the ductwork to identify, document, and report problem areas within the system
• Discuss findings and help HVAC contractors address problems and improve duct quality
• Train and teach builders, HVAC contractors, and other related parties on failure areas to minimize problems and increase confidence in future installations

The new requirement doesn’t necessarily mean every builder should adopt exactly the same testing sequence. But builders with recurring production should begin thinking now about whether rough-in testing, post-construction testing, or a defined combination makes the most sense for their workflow.

For production builders and multifamily projects, Stellar can work with your team to establish a repeatable duct-testing process instead of treating each test as a last-minute closeout item. Call us to discuss options or begin preparing for the upcoming code shifts, we would love to talk or set up a field visit to discuss.

R405 Is Getting Significantly Harder: 0.95 to 0.85

The removal of the duct-testing exception may be the most visible field change, but the change to R405 performance compliance could have an even broader effect on residential design.

Under the 2023 Florida Building Code, a project using the Simulated Performance Alternative can pass with a total e-Ratio of 0.95 or less.

Under the 2026 code, Section R405.3 reduces that maximum to 0.85. Florida DBPR describes this as a stringency increase of slightly more than 10 percent.

That is a substantial change.

To put the threshold itself in simple terms:

2023 code: e-Ratio ≤ 0.95
2026 code: e-Ratio ≤ 0.85

A house modeled at 0.90, which could satisfy the current threshold, would no longer satisfy the 2026 R405 threshold.

In fact, DBPR uses essentially that example in its official change guide: an example proposed design at 0.93 fails under the new requirement, while a design at 0.85 passes.

What Does the R405 e-Ratio Actually Mean?

R405 allows a proposed home’s calculated energy performance to be compared against a standard reference design. Instead of requiring every individual component to follow one fixed prescriptive package, the performance method allows tradeoffs among different aspects of the home’s design while still requiring the overall proposed design to satisfy the allowable performance threshold.

That’s one of the reasons the performance path is so useful in Florida residential construction.

A project may be able to compensate for one less-efficient component by gaining performance elsewhere. Depending on the project and the approved calculation methodology, improvements to the envelope, HVAC system, fenestration, duct system, infiltration assumptions, water heating, or other modeled components may contribute to the overall result.

But reducing the allowable e-Ratio from 0.95 to 0.85 gives the proposed design considerably less room.

Builders May Need to Find More Energy Credits

This is where I expect builders and energy-code professionals to spend a lot of time as the 2026 code begins affecting real projects.

Specifications that comfortably passed under the 2023 code may need to be reevaluated.

That doesn’t automatically mean every house will need the same upgrade. The whole point of the performance path is that the building is evaluated as a system.

One builder might find that HVAC efficiency provides the most practical improvement. Another design might benefit more from fenestration changes. Envelope specifications, duct location and leakage, air leakage sealing improvements, water heating, and other modeled characteristics can all become part of the conversation.

The important takeaway is that builders should not wait until a permit package is being finalized to find out whether an existing prototype still works at 0.85.

For production construction in particular, running representative plans and specifications through approved 2026 compliance software early can identify where changes may be needed and allow those decisions to be made deliberately rather than reactively.

The R405 Fenestration Limit Is Tightening Too

R405 includes another change worth watching.

For performance compliance, the maximum area-weighted average solar heat gain coefficient, or SHGC, for the Proposed Design is being reduced from 0.50 to 0.40, while the existing overhang exception is retained.

That is separate from the standard prescriptive vertical-fenestration requirements and matters specifically when modeling a project through R405.

For Florida homes with significant glazing, particularly custom and luxury residences with large window areas, fenestration packages should therefore be reviewed as part of the transition to the new performance calculations.

New Mechanical Ventilation Testing Is Coming

Another major field-verification change appears in new Section R403.6.3.

The 2026 Florida Building Code adds testing and verification requirements for mechanical ventilation system airflow. The requirement includes exceptions for certain kitchen range hoods, systems with qualifying integrated airflow diagnostic capabilities, and applicable unit sampling under R403.6.4.

This adds another potential testing and reporting component to residential closeout.

The 2026 forms also include a new Mechanical Ventilation Test Report for documenting airflow test results and pass/fail status.

This matters particularly when considered alongside Florida’s existing blower-door requirements.

Homes testing below 3 ACH50 continue to trigger the whole-house mechanical ventilation provisions. The PEG summary correctly identifies that existing relationship and notes that the 7 ACH50 maximum for Florida Climate Zones 1 and 2 remains.

Under the 2026 framework, however, required mechanical ventilation isn’t just something to account for in the design. The code now includes a field airflow verification component as well.

That means builders, HVAC contractors, mechanical designers, and testing providers need to be communicating before final inspection about what ventilation system is installed, what airflow is required, and how that airflow will be verified.

What About the R402 Prescriptive Path?

The 2026 code also makes substantial changes to prescriptive compliance, although for many of the Florida residential projects I encounter, R405 performance compliance is the more immediately relevant conversation.

The headline prescriptive change is new Section R407, Additional Efficiency Requirements.

Projects using the applicable R402 prescriptive compliance path must earn at least 10 credits from at least two measures. Homes with more than 5,000 square feet of above-grade living space require an additional five credits.

Available measures include options involving the building envelope, fenestration, HVAC performance, water heating, thermal distribution, renewable energy, demand-responsive thermostat controls, and lighting controls.

An important distinction is that this R407 credit system is associated with the applicable prescriptive compliance path. It should not be confused with the tightening of R405.

For builders already using R405, the more important issue is generally going to be getting the performance calculation down to 0.85 or below, not assembling an R407 prescriptive credit package. The R402 Prescriptive path has always been an incredibly stringent path, and it is rarely selected for a good reason.

Other Residential Energy Changes Worth Knowing

Although duct leakage testing and R405 are the changes I expect to generate some of the biggest conversations, they are not the only updates.

The 2026 Florida Building Code also includes several other residential changes worth putting on builders’ radar.

• Prescriptive skylight maximum U-factors decrease to 0.60, with maximum SHGC reduced to 0.28 in both Florida climate zones.
• New continuous-insulation options are added for wood-frame walls and floors.
• Attic access requirements receive additional gasketing, insulation, and installation provisions, along with additional eave-baffle requirements.
• Smart thermostats are added as an option within the applicable programmable thermostat provisions.
• HVAC equipment sizing provisions are revised to better address single-stage, two-stage, and multistage equipment and latent-capacity adequacy.
• New intermittent bathroom and toilet-room exhaust control requirements are introduced.
• The residential REScheck option previously identified in the Florida thermal-envelope alternative provisions is removed.
• Residential compliance forms are being updated to reflect the new requirements.

These changes deserve attention, but for most builders I work with, I would put R405 performance, duct leakage testing, mechanical ventilation verification, and HVAC sizing/latent performance near the top of the transition checklist.

What Florida Builders Should Be Doing Before December 31, 2026

Builders don’t need to panic over the new code, but they should prepare for it.

If I were sitting down with a builder today, my transition conversation would focus on four things.

First, identify which upcoming projects are likely to fall under the 2026 code. Don’t wait until closeout to determine which code edition governs the project.

Second, rerun common plans and specifications through approved 2026 compliance software. A prototype that passed R405 at 0.90 under the previous threshold is not going to pass a 0.85 requirement simply because the construction specifications haven’t changed.

Third, add duct leakage testing to the construction and inspection schedule unless the project legitimately qualifies for the remaining exception. That may also mean deciding whether rough-in testing should become part of the standard workflow.

Fourth, coordinate mechanical ventilation early. Particularly on tight homes, the mechanical designer, HVAC contractor, builder, and testing provider should understand the ventilation strategy before the project reaches final inspection.

The Florida Building Commission was already reviewing EnergyGauge USA and Right-Energy Florida compliance software for the 9th Edition at its September 4, 2026 meeting, which is another indication that the industry is moving from code development into actual implementation.

Why This Code Cycle Matters

For years, the R405 performance path has given Florida builders considerable flexibility in how they demonstrate energy-code compliance.

That flexibility isn’t disappearing.

But the target is moving.

A 0.85 e-Ratio requires better overall modeled performance than 0.95. The R405 duct-testing exception is disappearing. Mechanical ventilation is gaining a new field-verification requirement. Other envelope, HVAC, and documentation provisions are changing at the same time.

For builders who plan for those changes, this is manageable.

For project teams that continue using their 2023 assumptions until a permit reviewer, energy-calculation provider, inspector, or testing contractor tells them otherwise, the transition could create avoidable redesigns, testing surprises, failed inspections, and schedule delays.

And that’s exactly where I think an energy rater should be more than the person who arrives at the end of construction with a blower door.

At Stellar Building Performance, our goal is to help builders understand what the numbers mean, what the code is asking for, and how testing and building-performance decisions fit into the larger construction process.

If you’re a builder, developer, HVAC contractor, or project manager preparing for the 2026 Florida Building Code, contact Stellar Building Performance to discuss your upcoming projects. We can help plan for blower door testing, duct leakage testing, HERS ratings, energy-code compliance, and recurring testing needs before they become last-minute closeout issues.

2026 Florida Energy Code FAQ

When does the 2026 Florida Building Code take effect?

The 9th Edition (2026) Florida Building Code is scheduled to become effective December 31, 2026.

Does the 2026 Florida Building Code require duct leakage testing?

For R405 performance projects, the previous performance-path duct-testing exception is removed. Ducts generally must therefore be tested unless the project qualifies for the remaining exception for ducts and air handlers located entirely within the building thermal envelope.

Can I avoid duct leakage testing by using the R405 performance path?

Not under the 2026 code. The R405 exception that previously allowed this is being removed.

What is the new R405 e-Ratio requirement?

The maximum total e-Ratio decreases from 0.95 under the 2023 code to 0.85 under the 2026 code.

Would a 0.90 e-Ratio pass under the 2026 Florida Building Code?

No. R405.3 requires a total e-Ratio of 0.85 or less under the 2026 code.

Is blower door testing still required?

The 2026 changes discussed here do not eliminate Florida’s building-envelope air-leakage testing requirements. For Florida Climate Zones 1 and 2, the 7 ACH50 maximum remains, while homes below 3 ACH50 continue to require whole-house mechanical ventilation. The 2026 edition also adds mechanical-ventilation airflow testing where applicable.

Does R407 apply to R405 performance projects?

No. The new R407 additional-efficiency credit requirements apply to the applicable prescriptive compliance route, not R405 performance compliance.