What Software Is Title 24 Compliance Done In?
Performance compliance has to be demonstrated using CEC-approved software. CBECC is the Commission’s own program, and approved third-party tools exist — all of them following the same modelling rules, set by the Alternative Calculation Method manuals.
Approved, not merely capable
You cannot demonstrate performance compliance in a general energy modelling tool, however sophisticated. The program has to be approved by the Energy Commission for the relevant code cycle and occupancy type.
That is a genuine restriction rather than a formality. An unapproved tool may model the building more accurately in some respects and still be unusable for compliance, because compliance is a comparison against a defined baseline rather than a prediction of energy use.
The ACM manuals are the rulebook
The Alternative Calculation Method Approval Manual is adopted by regulation as an appendix of the Energy Code. It sets the requirements for input, output and calculational uniformity that any approved program must meet, and the ACM reference manuals define the modelling rules the software applies.
This is why two approved programs should reach the same compliance answer for the same building. They are not competing simulation engines free to disagree — they are implementations of one published ruleset.
What the software is actually comparing
Performance compliance models the proposed design against a standard design derived from the prescriptive requirements, and asks whether the proposal uses no more energy. The baseline is generated by the ruleset from your building's own geometry and use — it is not a fixed target.
That mechanism is what lets the performance path work as a trade. A generous glazed area can be offset by better performance elsewhere, because both designs are being run through the same rules and only the totals are compared.
Software changes with the code cycle
Each code cycle brings its own approved versions, because the ruleset itself changes. A model built in a previous cycle's version does not simply carry forward — the baseline it was compared against is no longer the current baseline.
For a project spanning a cycle change this is a real consideration, and it is one of the reasons a report tied to a superseded cycle cannot support a new permit application.
Why this matters when choosing a provider
Ask which approved software they use and which cycle's version. It is a specific, checkable question, and it distinguishes someone working inside the approved framework from someone producing documents that look right and were not generated by an approved tool at all.
The prescriptive path, worth noting, does not require software — it is a compliance route assessed against the requirements directly. Software is the performance path's instrument, which is why the choice of route comes first and the choice of tool second.