Does a modular commercial building need Title 24?

Yes, where it is a building under the California Building Code. Part 6 has no modular category, so it meets the nonresidential standards for its occupancy exactly as a site-built building would.

Who reviews Title 24 for a relocatable classroom?

The Division of the State Architect. Appendix NA4 describes its two steps: a pre-check approval of the model, then an over-the-counter application for each site or stockpile.

Can a relocatable classroom be installed in any climate zone?

Only if it was certified for all zones under Table 140.3-D and labelled accordingly. A unit certified under Table 140.3-B may be installed only in the climate zones it was certified for.

Does moving a relocatable classroom trigger Title 24?

Not by itself: a note to Section 141.0 says relocation is not an alteration. Work that changes the building's components, such as new HVAC or lighting, follows the alteration rules of Section 141.0(b).

Title 24 for Modular and Relocatable Buildings

The Energy Code has no separate category for modular or factory-built commercial buildings, so a modular office or clinic meets the same nonresidential standards as a site-built one. The exception is the relocatable public school building, which is certified for specific climate zones under Table 140.3-B or for all of them under Table 140.3-D, and carries two metal identification labels.

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No modular category in Part 6

The Energy Code sorts buildings by occupancy, not by how they are built. Section 100.1 defines a nonresidential building by its California Building Code occupancy group, and nothing in the scope or definitions creates a class for modular, prefabricated or factory-built commercial buildings. The CEC's nonresidential manual says the standards apply to CBC occupancies A, B, E, F, H, I, L, M, S and U, and do not apply to buildings outside the CBC's jurisdiction, such as mobile structures.

A modular office, clinic or retail unit permitted under the CBC is therefore assessed like a site-built building of the same occupancy: mandatory measures, envelope, HVAC, lighting and, where they apply, PV and batteries. The factory changes where the work is done, not which requirements apply, and the requirements by building type read the same. Housing follows the same logic: the CEC's ADU guidance says factory-built homes must comply with Title 24, including the Energy Code, while HUD-labelled manufactured homes come under Title 25 and are not subject to it.

Relocatable public school buildings

The one factory-built type the Standards name is the relocatable public school building, defined in Section 100.1 by reference to Part 1, Section 4-314. One model may be shipped anywhere in the state, so Section 140.3(a)8 lets the manufacturer or builder certify it in one of two ways:

For specific climate zones: the envelope meets Table 140.3-B for each zone certified, and Appendix NA4 says the unit may not lawfully be installed anywhere else.
For every climate zone: the envelope meets Table 140.3-D, a single set of statewide criteria.

The building carries two metal identification labels, mechanically fastened: one visible from outside and one on the interior frame above the ceiling at the end of the module. A statewide unit's labels read "Complies with Title 24, Part 6 for all climate zones", a climate-specific unit's label names its zones, and the plans show where the labels are. Relocatables are also excepted from the continuous air barrier requirement of Section 140.3(a)9.

Eight orientations in the performance model

Reference Appendix NA4 sets the performance procedure. A relocatable can end up facing any direction, so the same proposed design is rotated through eight orientations in 45-degree steps and must comply in every case: in climate zones 14, 15 and 16 for a statewide unit, or in each zone the manufacturer certifies. The standard design keeps the proposed geometry and window positions with the prescriptive envelope, lighting and HVAC of Sections 140.3, 140.6 and 140.4. Approved software automates the rotation and flags the case with the smallest margin, which is documented in full.

Which code edition applies

The Division of the State Architect is the enforcement agency, and approval comes in two steps: a pre-check (PC) approval of the model's design, then an over-the-counter application to build units for a site or for a stockpile, and another to place a stockpiled unit. NA4 states that the permit application date for the Energy Code is the over-the-counter date, and that a PC design is valid only until the code changes. A model pre-checked under the 2022 code is held to the 2025 Energy Code once its over-the-counter application is made on or after 1 January 2026.

Moving one later

A note to Section 141.0 says that relocating or moving a relocatable public school building is not, by itself, an alteration. Changing its components is: Section 141.0(b) applies the alteration rules to relocatable public school buildings as to other nonresidential buildings. The note names only relocatable public school buildings, so how a relocated commercial unit is treated is a question for the building department. Classroom ventilation and lighting are covered under Title 24 requirements for schools.