Is a Blower Door Test Required in California? Title 24 Air Leakage Testing
Not for a typical house. Title 24 requires a blower door test only when you choose it: for an energy credit, to use a leakage rate below 2 ACH50 in ventilation sizing, or to qualify for the R-4.2 duct exception in an unvented attic. Additions can also use a tested value in load calculations. A typical remodel has no such test.
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Where a test can come up
- Performance credit. Section 150.1(b)2Bviii says enclosure leakage is field verified when the compliance model uses a rate lower than the standard design. The manual puts the standard design at 5 ACH50 and pays no credit for an exterior air wrap or for QII alone.
- Ventilation sizing. The fan-flow equation in Section 150.0(o) assumes 2 ACH50 with no test. A measurement is needed only when the model uses less than 2.
- Ducts in an unvented attic. R-4.2 duct insulation replaces R-6 only if the attic has at least R-30 at the roof deck, the gable ends meet the wall rules and the home tests at 3.0 ACH50 or less. The manual runs that test with the attic hatch open.
- Additions. Load calculations use the infiltration values in Table 150.2-C, or a tested value from Appendix RA3.8 with no disclosure needed.
Three numbers, three meanings
Keep the figures apart. Two is the default assumed for ventilation, three is the pass line for the duct exception, and five is the energy standard design that credits are measured against. A house tested at 4 ACH50 beats the 5 but fails the 3.
What the test measures
A fan in a doorway pressurizes the closed-up house to 50 Pa and records airflow in CFM50. Appendix RA3.8 follows RESNET 380 and can report CFM50, ACH50 or CFM50 per square foot of enclosure, whichever the compliance document asks for. An ECC-Rater runs it, and the result is registered. It is a different test from duct leakage; see duct leakage testing.
Where it does not apply
The alteration list in Section 150.2(b)1, items A to N, has no enclosure leakage test, so a typical remodel needs none. Commercial buildings follow separate nonresidential rules. For the sealing work that precedes any test, read air sealing and air barrier requirements.
See whole-house ventilation, unvented attics and when ECC-Rater verification is required. Our residential reports state which tests your plan needs.
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
Not under Part 6 for a typical house. A test is tied to a credit you claim, a ventilation or duct choice that depends on it, or an addition load calculation that uses a tested value.
An ECC-Rater (the role formerly called a HERS rater, renamed on 1 January 2026) runs it, following Appendix RA3.8, and the result is registered with the ECC-Provider.
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View all Insulation guides → · Windows and Building Envelope · Title 24 guide