Title 24 duct testing and ECC verification for HVAC replacements

If you are replacing an air conditioner, furnace or heat pump in California, Title 24 duct testing is almost certainly part of the job. Fallbrook Heating & Air treats Title 24 duct testing as a standard part of every qualifying changeout, and we pull and file all legally required permits for North County homeowners. Here is what the test is, why it is required, and what to expect on the day.

What is Title 24 duct testing?

Title 24 duct testing is a measured check of how much air leaks out of your home's ductwork, required by California's Building Energy Efficiency Standards (Title 24, Part 6) when major HVAC equipment is replaced. Leaks found are sealed, and an independent ECC-Rater, formerly called a HERS rater, verifies the result before the permit is closed.

Ducts usually run through the attic or crawlspace. Every gap in a joint or connection leaks cooled or heated air into a space you are not trying to condition, and on the return side pulls dusty attic air back in. Older ducts can leak a surprising share of the air your system moves, which means you pay to condition air that never reaches a room.

When is duct testing required?

Under California's 2025 Energy Code, in effect since January 1, 2026, replacing an air handler or furnace, an outdoor AC or heat pump unit, or an indoor coil triggers duct sealing plus third-party verification. Additional verification can apply depending on the equipment and the climate zone. Repairs that do not replace those components generally do not trigger it.

• New outdoor AC or heat pump unit: typically triggers testing
• New furnace or air handler: typically triggers testing
• New indoor coil: typically triggers testing
• Full system replacement: triggers testing, plus any other verification required for the equipment
• Routine repairs such as a capacitor, motor or igniter: generally not

We confirm the exact requirements for your equipment and location when we pull the permit. Our guide to permits and Title 24 in San Diego County goes deeper, with links to the California Energy Commission.

How does the duct leakage test work?

A calibrated fan is connected to the duct system, usually at the air handler or a return grille, while the supply registers are temporarily sealed. The fan pressurizes the ducts and measures how much air it takes to hold that pressure, which equals the leakage. Leaks are sealed and the ducts retested until they pass.

1. Prepare. Registers and grilles are temporarily covered so the duct system is closed.
2. Test. The test fan pressurizes the ducts and records the leakage.
3. Seal. Leaks at joints, boots, plenums and connections are sealed with code-approved materials such as mastic.
4. Retest. The ducts are tested again to confirm they meet the code limit.
5. Verify. An independent ECC-Rater checks the result and registers it, which lets the permit be finaled. We contract a licensed rater and schedule the visit for you.

What if my ducts fail the test?

We seal them and they are tested again. When we replace only the equipment and keep your existing ducts, the ducts and equipment together must leak no more than 15%. If they test above that, we seal the leaks we can reach (joints, register boots, plenum connections and the air handler cabinet), then the licensed ECC-Rater (HERS rater) we contract confirms a passing test. If the ductwork itself is replaced, the new ducts must test at 5% leakage or less.

A failed first test is common on older homes and is not a sign anything was done wrong; it is exactly what the test is meant to find. The sealing work needed to pass is discussed up front, so it does not arrive as a surprise on installation day.

What changed from HERS to ECC?

Mostly the name and the program behind it. Starting with the 2025 Energy Code on January 1, 2026, California runs third-party field verification through the Energy Code Compliance (ECC) program instead of the HERS program, and raters are now called ECC-Raters. The core idea is unchanged: someone independent of the installer confirms the work meets code.

You may still see "HERS test" on older paperwork and in conversation. It refers to the same kind of verification.

Who issues the permit for my area?

It depends on whether you live in an unincorporated community or a city. Unincorporated Fallbrook, Bonsall, Rainbow and De Luz go through San Diego County Planning & Development Services. Cities like Oceanside, Vista, Escondido and Temecula issue their own permits through their building departments. We pull and file the permit for you either way.

Why does duct testing matter to you, not just the inspector?

Because a new high-efficiency system connected to leaky ducts will not deliver what you paid for. Sealing the ducts gets more of the conditioned air into your rooms, can reduce run time and dust, and the permit and verification record is proof the work was done properly when you sell the house.

It also helps comfort. A room at the end of a long, leaky duct run is often the one that never cools. Sealing does not fix every uneven-temperature problem, but it is the right first step before considering zoning.

Where we work: we handle permits and Title 24 testing on replacements across North County, including Bonsall and Fallbrook through the County, and city permits in Vista and Temecula. If you are planning an AC replacement, a new furnace or a heat pump, testing is part of the job from the first estimate. Call (760) 728-8716.