When Is Title 24 Required for a Home?
Whenever the work adds conditioned floor area, changes the building envelope, or installs or alters heating, cooling or water-heating equipment. The trigger is the scope of work, not the age or type of the house.
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Three ways a house comes into scope
New construction is covered in full. An addition — any new conditioned floor area — is covered under the addition provisions. An alteration, which is work on what is already there, is covered to the extent of what it touches. Most residential projects are the second or third, and the difference decides how much documentation is needed.
What does not need a report
Genuinely cosmetic work is outside the Energy Code. New flooring, paint, cabinetry, interior doors, a bathroom refit that reuses the existing openings and equipment — none of that is regulated. Replacing like-for-like where nothing regulated changes is generally outside it too.
What catches people is that a single regulated item pulls the project in. Swapping a furnace, replacing windows, adding insulation, or bringing an unheated room into conditioned use each does it on its own, without any addition at all.
Why two identical houses get different answers
Because the answer follows the drawings rather than the address. Two neighbours with the same floor plan can reach opposite conclusions if one is reglazing the front elevation and the other is only redoing the kitchen. That is also why "my contractor said we don't need it" is worth checking against the actual scope — the contractor may be right about the work they are doing and wrong about the work as permitted.
The current standards apply to permit applications submitted on or after 1 January 2026, so calculations prepared under the previous edition do not automatically carry to an application filed now.