Duct Leakage Testing: When Is It Required Under Title 24?
In an existing house the test follows the work: a replaced air handler, outdoor unit or coil, more than 25 feet of new or replacement duct, or ducts extended to an addition. Pass numbers run from 5 to 10 percent of airflow, with 6 percent in a garage. A house with no ducts needs no test.
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Find the trigger, read off the number
- New or replaced equipment. An air handler, the outdoor unit of a split system, a complete packaged unit or a coil: 10 percent total leakage or 7 percent to outside (Section 150.2(b)1E). Skipped for under 40 linear feet of duct, ducts already sealed and verified, or asbestos.
- More than 25 feet of new or replacement duct. 5 percent if the result is an entirely new system, otherwise 10 or 7 percent (Section 150.2(b)1D).
- Ducts extended to an addition. Any length, 10 or 7 percent, tested on the combined system.
- Anything altered in a garage. 6 percent, or a smoke test, at any length.
- No ducts. No test.
From percent to cubic feet per minute
The limit is a share of air handler airflow, measured with the ducts at 25 pascals. A single indoor unit is credited with 400 cfm per ton, so a 2.5-ton system counts as 1,000 cfm: 50 cfm at 5 percent, 100 at 10 percent, 70 at 7 percent to outside, 60 in a garage.
Who does what, in what order
The installer tests and registers CF2R-MCH-20-H, and the ECC-Rater, the role called a HERS rater until 1 January 2026, confirms it and signs CF3R-MCH-20-H. Where altered ducts miss the numbers, the fallback is not a shortcut: measure, seal every accessible leak, measure again, then the smoke test and a visual check of boots, plenum and cabinet joints. Sampling is not allowed.
What a failure does to the schedule
A failed result is entered in the registry, and the ECC-Rater who registered it becomes the Rater of Record. Only that rater or company may register the later pass, unless the provider releases the project and checks the retest. The failed form prints only with a FAIL watermark, and a passing form exists only after the correction and retest.
The general rule is on duct leakage testing, the small-dwelling version on the ADU page, and the 25-foot trigger on duct replacement. See also failed tests and residential reports.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
No. The triggers in Section 150.2(b)1D and 1E are new or replacement ducts, and equipment such as the air handler, outdoor unit or a coil.
Six percent of airflow, which is 60 cfm on a 1,000 cfm system, or all accessible leaks sealed and verified by a smoke test and visual inspection.
Explore Ducts
- When Is Duct Leakage Testing Required?
- Duct Replacement 25-Foot Rule Under Title 24
- Ducts in Soffits and Conditioned Space: Do They Need Insulation?
- Extending Existing Ducts to an Addition: Title 24 Rules
- Flexible Duct Installation Rules Under Title 24
View all Ducts guides → · HVAC and Water Heating · Title 24 guide