What is Title 24?

The parts map to the disciplines at the table: Part 1 is administrative; Part 2, the California Building Code, carries structural and life-safety requirements on the framework of the International Building Code; Part 2.5 covers dwellings; Parts 3, 4, and 5 govern electrical, mechanical, and plumbing work; Part 8 addresses historic buildings, Part 9 is the Fire Code, Part 10 covers existing buildings, and Part 12 collects referenced standards. A design team lives mostly in Parts 2 through 6 and 11 — and a correction list citing Title 24 can come from any of them. The whole code is republished on a three-year cycle: the 2022 edition took effect January 1, 2023, and the 2025 edition takes effect January 1, 2026, with the edition in effect at permit application generally governing the project.

• Part 2 (CBC) carries structural and life-safety requirements
• Parts 3, 4, and 5 govern electrical, mechanical, and plumbing work
• Part 6 is the energy code — the usual meaning of the shorthand
• Part 11 (CALGreen) runs alongside Part 6

Part 6 deserves the closest look, because it is the part that generates work on ordinary projects. The energy standards were first adopted in 1978 and are updated by the California Energy Commission on the same three-year rhythm, to reduce the energy cost and peak demand of buildings over their operating lives. Part 6 regulates the building envelope — insulation, fenestration, air leakage — together with space conditioning, service water heating, indoor and outdoor lighting and controls, and pool and spa equipment. Recent cycles added solar and battery requirements for many new buildings. California is divided into sixteen climate zones, and requirements differ by zone: what complies in coastal San Diego does not automatically comply in the Central Valley or the mountains. Above all of it sits a layer of mandatory measures that apply under either compliance path.

• Regulates envelope, HVAC, water heating, lighting, and pool and spa systems
• Sixteen climate zones, with requirements that differ by zone
• Mandatory measures apply under both compliance paths
• Recent cycles added solar and battery requirements for many new buildings

There are two ways to comply, and choosing between them is a genuine design decision. The prescriptive approach is a checklist: every regulated component meets its prescribed value — wall assembly, window U-factor and solar heat gain, equipment efficiency, lighting power allowance — with no trade-offs between components. It is fast and predictable for small, conventional buildings, and rigid the moment a design departs from the tables, as a glass-heavy storefront quickly does. The performance approach instead models the whole building in software approved by the Energy Commission — CBECC-Res for residential work and CBECC-Com for nonresidential, plus approved commercial alternatives — and compares the proposed design's modeled energy use against a standard-design baseline generated from the prescriptive rules. Beat the baseline and the design complies, which lets a team trade a more efficient mechanical system or better lighting controls against the storefront glazing the prescriptive path rejected. Most substantial commercial projects take the performance path; most small residential projects stay prescriptive.

• Prescriptive: every component meets its table value, no trade-offs
• Performance: modeled whole-building energy use must beat a standard-design baseline
• CEC-approved software includes CBECC-Res and CBECC-Com
• Performance path enables trade-offs between systems

Compliance is proven on paper, in three stages, and the paper trail is what plan check actually reviews. At design, the team registers and completes the certificate of compliance — the CF1R for residential projects, the NRCC for nonresidential — which enters the permit set and states the path, the inputs, and the margin. During construction, installers complete installation certificates — CF2R or NRCI. At final, verification certificates — CF3R or NRCV — cover measures requiring field verification, some performed by a certified HERS rater independent of the installer. Nonresidential controls additionally require acceptance testing by a certified technician before final inspection. The forms are prepared by a documentation author; the responsible designer signs for the design's compliance, and the recognized specialist credential in this work is the Energy Commission's Certified Energy Analyst designation. A set that reaches plan check with the wrong forms or inputs that do not match the drawings will draw energy comments just as surely as a structural set with missing calculations.

• Design stage: CF1R (residential) or NRCC (nonresidential) certificate of compliance
• Construction stage: CF2R / NRCI installation certificates by the installers
• Final stage: CF3R / NRCV verification certificates, some by an independent HERS rater

Part 11, CALGreen, runs alongside Part 6 and is frequently confused with it. Its mandatory measures are not, for the most part, energy calculations: waste diversion, indoor water reduction, low-emitting materials, bicycle parking, and electric vehicle charging scaled to the parking count. Its voluntary Tier 1 and Tier 2 measure sets matter because many cities adopt a tier, in whole or in part, as their local reach standard — so the CALGreen checklist in the permit set may be the statewide floor or a stricter local version, and the team has to establish which before the set is drawn. I ask about local amendments at the start of every California project, because designing to the state floor in a reach-code city is a correction cycle waiting to happen.

• CALGreen mandatory measures cover water, waste, materials, and EV charging
• Tier 1 and Tier 2 sets are often adopted locally as reach standards
• Reach energy codes can exceed Part 6, including all-electric requirements
• Confirm the local amendment package before the set is drawn

Title 24 hits every California permit applicant — owners, architects, engineers, and builders — on new buildings, and on additions and alterations to the extent the alteration rules reach. Those trigger rules are specific: a roof replacement, an HVAC changeout, a window replacement, and a lighting alteration each carry their own Part 6 requirements for the work being done, while an untouched existing building is not retroactively dragged into current compliance. Additions must comply for the new work, and some measures look at the combined existing-plus-addition condition. Outside California, Title 24 has no force at all, and California does not adopt the IECC used elsewhere — out-of-state models, forms, and software do not transfer. For the documentation itself, as typical market ranges: a prescriptive residential report for a production-style home commonly runs a few hundred dollars; a custom home, an ADU with a performance run, or a small commercial report more commonly falls between roughly five hundred and fifteen hundred dollars; and a nonresidential performance model with the full NRCC package starts in the low thousands and rises with size and complexity, with HERS verification and acceptance testing billed as separate field services. What the fee buys is not the form; it is the analysis that keeps the energy review from becoming a correction cycle.

• Alterations trigger Part 6 requirements specific to the work being done
• Untouched existing buildings are not retroactively brought into compliance
• California does not adopt the IECC — out-of-state documentation does not transfer
• Documentation ranges from a few hundred dollars (residential) to the low thousands and up (nonresidential models)

Consider a new 6,800-square-foot retail shell in Climate Zone 12, in the Sacramento Valley, with a storefront-heavy elevation. Run prescriptively, the design fails: the glazing cannot meet the prescriptive fenestration limits alongside the lighting design as drawn. The team moves to the performance approach. The CBECC-Com model holds the storefront, and the design earns its margin back with higher-efficiency rooftop units, a tighter envelope specification, and occupancy and daylighting controls in the sales area — measures the team has to actually draw, not just model. The NRCC certificate enters the permit set with its compliance margin printed on it, the energy reviewer checks model inputs against the drawings, and construction proceeds with NRCI certificates, acceptance testing, and the triggered verification steps, each closed before final inspection — the standard shape of a California commercial project, and why energy work starts with the design, not after it. Apex Grid Engineering PLLC prepares Title 24 Part 6 documentation — prescriptive reports and performance energy models, with the CF1R and NRCC certificates coordinated to the permit drawings — as part of California MEP and permit packages; to scope a project, send the address and the architectural set or a description of the building, or call 480-490-0064.

• Prescriptive path failed on fenestration limits for the storefront design
• Performance model traded HVAC efficiency and lighting controls for the glazing
• NRCC certificate submitted in the permit set with the compliance margin shown
• Installation certificates, acceptance testing, and verification closed before final