What Is Exempt From Title 24?
Less than most people hope. There are real exemptions — qualified historic buildings, two occupancy groups, and temporary work at the building department’s discretion — but no general exemption for small projects or for older buildings.
Qualified historic buildings, partly
A qualified historic building, as regulated by the California Historical Building Code (Title 24 Part 8), is exempt from the Energy Code's general application provision. That is a genuine and substantial exemption.
But it is partial. Lighting still has to comply with the applicable requirement, and the lighting exemption from the power allowances applies only where the indoor and outdoor lighting consists solely of historic lighting components or replicas of them. Fit modern luminaires into a historic building and the lighting power allowance applies as it would anywhere.
And non-historical additions comply in full. Extending a historic building does not extend its exemption to the new work.
Occupancy Groups I-3 and I-4
These two groups are excluded from coverage. It is a narrow carve-out defined by occupancy classification rather than by anything about the building's construction, and either it applies to your project or it plainly does not.
Temporary work — but only at the department's discretion
Building departments may exempt temporary buildings, temporary outdoor lighting, temporary lighting in an unconditioned building, and structures erected in response to a natural disaster.
The permissive wording is the whole point. This is not an exemption a project can claim — it is one a jurisdiction can grant. Two departments can reasonably reach different answers on identical temporary work, so it is a conversation to have with the department rather than an assumption to build a programme on.
What is not an exemption
Project size. There is no threshold below which the Energy Code stops applying — small alterations engage requirements scaled to what changed, rather than falling outside the code.
Building age. An old building is not exempt; it is subject to the alterations requirements, which are written specifically for existing buildings.
Being unconditioned. Unconditioned space is inside the code's reach in several places — lighting applies, and the prescriptive daylighting requirement for large spaces explicitly covers unconditioned as well as conditioned spaces.
The more useful question
Rather than whether a project is exempt, ask which requirements its scope actually engages. That question has a definite answer, and it is usually a much shorter list than the owner feared — which achieves what looking for an exemption was really trying to achieve.