Does an HVAC Replacement Need Title 24?
Usually yes. Replacing the air handler, the outdoor condensing unit of a split system, or a heating or cooling coil is an alteration under the Energy Code, and it triggers duct sealing requirements.
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Why a like-for-like changeout is still regulated
This surprises people, because nothing about the house is changing. But the code names these replacements specifically: swapping the air handler, the outdoor condensing unit of a split-system air conditioner or heat pump, or a cooling or heating coil is an alteration that brings the duct system into scope along with the equipment.
The duct thresholds
If more than 40 linear feet of new or replacement space-conditioning duct is installed, the entire duct system has to be sealed and leakage tested, and it has to come in at 15 per cent leakage or less. That is a whole-system test, not a test of the new section — the new run is what triggers it, but the old ducting is what usually fails it.
There are exemptions from the leakage test. If fewer than 25 feet of duct were added or replaced, it does not apply. Nor does it if the existing ducts are insulated with asbestos, or if the system has already been tested and passed by a HERS rater.
What that means for the paperwork
Where an altered space-conditioning system is not exempt from field verification, the alteration form has to be completed and registered with a HERS provider's data registry, and a rater has to verify the work. That is a scheduling dependency, not just a document: the test happens on site, with the system installed.
The practical read
A straight condenser swap that touches almost no ducting is a light-touch job. The same swap on a house being reducted is a different project, and the duct test is the part most likely to fail first time in an older house. Establishing roughly how much duct is being replaced, before the work starts, is what decides which of those two you are in.