What Is Title 24 and What Does It Mean for Your Remodel?

CALIFORNIA REMODELING | PERMITS AND PROJECTS

If your California remodel involves windows, insulation, lighting, HVAC, ventilation, roofing, or water heating, you may hear that something “needs Title 24.” That phrase is common, but it can hide several different requirements.

Title 24 can affect what your project is allowed to install, what must appear on the plans, which forms accompany the permit application, and whether completed work requires independent testing. The answer depends on the actual scope, the building’s climate zone, the compliance method, and applicable local requirements.

Here is what homeowners need to understand before plans are submitted, equipment is ordered, or contractor proposals are compared.

Title 24 is the building code, but the name is often used as shorthand

Title 24 is the California Building Standards Code. It includes the building, residential, electrical, mechanical, plumbing, fire, accessibility, energy, and green-building codes, among others.

The energy requirements are primarily found in Title 24, Part 6, officially called the California Energy Code or the Building Energy Efficiency Standards. When a contractor, designer, energy consultant, or building department says, “We need Title 24,” they usually mean compliance with Part 6.

The California Energy Commission develops and updates the Energy Code. The city or county building department reviews the project, issues the permit, performs inspections, and enforces the code. A jurisdiction may also have lawfully adopted local requirements that go beyond the statewide minimum.

The 2025 Energy Code took effect January 1, 2026. It applies to buildings whose permit applications are submitted on or after that date. Earlier applications are generally reviewed under the code edition in effect when the application was made, subject to the building department’s rules and the status of that application.

What does the California Energy Code regulate?

For a home, Title 24, Part 6 can regulate energy-related features including:

• Insulation and parts of the building envelope
• Windows, skylights, and glazed doors
• Heating and cooling equipment
• Duct systems
• Ventilation
• Water-heating systems and some hot-water piping
• Hardwired interior and exterior lighting
• Certain roof assemblies and roofing products
• Electric-readiness measures when they apply to the proposed scope

You will frequently see the word fenestration. This is the code term for windows, skylights, and glazed doors. A door with glazing covering 25 percent or more of its area is treated as a glazed door under the residential requirements.

Fenestration performance is commonly described using two ratings:

• U-factor measures heat transfer through the complete product. Lower is generally better.
• Solar Heat Gain Coefficient, or SHGC, measures how much solar heat passes through the product. A lower number allows less solar heat through.

The applicable limits are not universal. They can change with the climate zone, project type, product type, area, orientation, compliance method, and available exceptions.

Three layers of compliance

Mandatory requirements

Applicable mandatory measures must be met regardless of the compliance method. They establish minimum requirements for items such as product certification, air sealing, lighting, insulation, controls, equipment, and installation. A performance model cannot trade away an applicable mandatory minimum.

Prescriptive compliance

The prescriptive method is the direct path. Each affected component must meet its assigned requirement for the project and climate zone, including any applicable exceptions. A straightforward alteration may be able to comply this way without a whole-building energy model.

Performance compliance

The performance method uses California Energy Commission-approved software to compare the proposed design with a code-defined standard design and energy budget. It can allow trade-offs when the prescriptive path does not fit, but mandatory measures still apply.

Performance compliance may be useful when a project has substantial glazing, unusual assemblies, several interacting systems, or a design choice that does not satisfy a prescriptive requirement. It is an available compliance path for many additions and alterations. It is not required simply because a project is large or architecturally interesting.

When does Title 24 apply to a remodel?

The Energy Code applies to additions and alterations. Work that qualifies only as a repair is generally treated differently. The classification depends on what is actually changing, not the label used in a proposal.

• Addition: Work that increases the conditioned floor area and conditioned volume. Converting an unconditioned garage or similar area into conditioned living space can also be treated as an addition.
• Alteration: A change to an energy-regulated system or the building envelope that is not an addition. Common examples include replacing windows, changing hardwired lighting, replacing HVAC equipment, altering ducts, reroofing, or replacing a water heater.
• Repair: Maintenance that restores or renews an existing part of the building. Replacing a regulated component or system may still be classified as an alteration even if the proposal calls it a repair.

Whether a permit is required and which Energy Code provisions apply are related questions, but they are not identical. The building department makes the final determination for a specific project.

Common remodeling scopes

• Paint, flooring, cabinets, and countertops only: Generally no Energy Code documentation solely for this work, provided the project does not include regulated lighting, envelope, mechanical, ventilation, or water-heating work.
• Hardwired lighting: New or altered lighting must meet the applicable residential lighting requirements. This does not ordinarily require a whole-building energy model.
• Replacement windows, skylights, or glazed doors: Product ratings, area, climate zone, and exceptions determine the requirements. The limited exception for up to 75 square feet of replacement vertical fenestration relaxes certain prescriptive values. It does not make the work exempt from the Energy Code.
• New window or glazed-door area: Total area, west-facing area in certain climate zones, U-factor, SHGC, and the chosen compliance method may matter.
• Water heater or hot-water piping: Equipment, controls, and pipe-insulation requirements depend on the exact work.
• HVAC equipment or ducts: Equipment standards, sizing, duct sealing, airflow, refrigerant-charge verification, controls, and exceptions depend on the system and components being altered.
• Roofing or attic work: Cool-roof, insulation, air-sealing, and related provisions depend on climate zone, roof slope, existing conditions, and applicable exceptions.
• Conditioning previously unconditioned space: This can be treated as an addition. Prescriptive and performance paths may both be available.
• Whole-house renovation: Requirements apply to the components and systems being altered. A broad renovation does not automatically require performance compliance in every case.

This is a planning guide, not a substitute for project-specific code review. Small scope changes can change the answer.

Climate zone and jurisdiction matter

California uses 16 Energy Code climate zones. Requirements for windows, roofs, insulation, HVAC testing, and other measures can vary by zone.

Do not assume that all of Orange County, or every address in a ZIP code, is in the same climate zone. Check the project address using the California Energy Commission’s Climate Zone Tool, then confirm the result and any local requirements with the building department.

What does compliance look like during the project?

Title 24 compliance is not one form completed at the end. Depending on the scope, documents and responsibilities appear at several stages.

During design and plan check: CF1R

The Certificate of Compliance, or CF1R, documents how the proposed design complies. The correct form depends on the scope and compliance method. Some projects require registration through an approved Energy Code Compliance provider, while eligible prescriptive projects without field verification may use non-registered forms.

The person designing the building may delegate preparation of the energy analysis and compliance documents to a documentation author or energy consultant. The responsible designer still approves and certifies the design information as required.

During installation: CF2R

The applicable contractor or installer completes a Certificate of Installation, or CF2R, for regulated features installed during construction. It confirms that the work conforms to the approved plans, specifications, and compliance documents.

This is why substitutions matter. Changing a window, water heater, HVAC unit, or another specified component may alter the assumptions used for compliance. The documentation or approval may need to be updated before installation.

When independent verification is required: CF3R

Some measures require field verification or diagnostic testing by a certified Energy Code Compliance Rater, or ECC-Rater. The rater completes a Certificate of Verification, or CF3R. You may still hear the older and familiar term HERS rater, particularly when people discuss earlier code cycles.

HVAC work often triggers this step. Requirements can include duct leakage testing, airflow measurements, fan efficacy, refrigerant-charge verification, or other measures. Exceptions can depend on which components are replaced, where ducts are located, whether a system was previously certified, and other existing conditions.

Under the 2025 requirements, refrigerant-charge verification applies prescriptively to split-system heat pumps in all climate zones and to split-system air conditioners in Climate Zones 2 and 8 through 15. Project-specific exceptions and the selected compliance method still matter.

When is energy modeling actually needed?

The chosen compliance strategy determines whether the project uses energy modeling. There is no universal project-size rule.

The prescriptive path is often practical when every affected component can meet its requirement, the glazing design fits the applicable limits or exceptions, and the HVAC, roof, insulation, lighting, and water-heating choices do not need trade-offs.

The performance path may be appropriate when a proposed feature does not satisfy a prescriptive requirement but better performance elsewhere can offset it, the project includes a complex glazing design, several additions and alterations are being evaluated together, or modeling offers a more workable route than changing the design.

A small addition does not automatically avoid modeling, and a large renovation does not automatically require it. The design, affected systems, exceptions, and compliance choices control.

What changed with the 2025 Energy Code?

The 2025 Energy Code applies to permit applications submitted on or after January 1, 2026. Its most publicized residential change is the expanded use of heat pumps in newly constructed homes, including heat-pump prescriptive baselines for space and water heating.

That does not mean every California homeowner replacing an existing gas furnace must install a heat pump. Additions and alterations have their own requirements. Existing-system decisions depend on the fuel, replacement equipment, affected components, compliance path, and applicable local rules.

The practical lesson is simple: identify the proposed HVAC scope and compliance requirements before equipment is ordered. Broad statements that the new code either “requires heat pumps” or “does not affect replacements” are both unreliable.

What this means for your scope and contractor proposals

Title 24 is another reason to define the project before collecting final bids. A contractor cannot accurately price documentation, product performance, testing, coordination, and corrective work when those obligations have not been identified.

Determine as early as practical:

• Which code edition applies
• The project’s Energy Code climate zone
• Whether applicable local requirements go beyond the statewide minimum
• Which parts of the work are additions, alterations, or repairs
• Whether prescriptive or performance compliance is anticipated
• Which product ratings and system characteristics must appear on the plans and CF1R
• Whether field verification or diagnostic testing is required
• Who prepares, signs, registers, submits, and retains each compliance document
• Whether the proposal includes energy analysis, registry fees, rater fees, return visits, corrections, and retesting

Questions to ask before signing

• Which parts of this scope are regulated by Title 24, Part 6?
• Are you assuming prescriptive or performance compliance, and why?
• Who will prepare and coordinate the CF1R with the plans?
• Which CF2R forms will the installers complete?
• Which measures require an ECC-Rater, and who is coordinating that work?
• Are analysis, registration, testing, return visits, and possible retesting included?
• Which product or equipment criteria must be finalized before permit submittal?
• What happens if a specified product changes after the permit is issued?

Two proposals can appear to cover the same remodel while making different assumptions about Title 24 documentation and testing. If one includes those obligations and the other quietly leaves them to the homeowner, the bids are not truly comparable.

How Master Build Advisor helps

Master Build Advisor provides homeowner-focused planning and consulting. During early planning, we identify likely Title 24 triggers, flag specifications that may need to be established before permit submittal, and help define responsibility for required documentation and testing.

The final code determination belongs to the building department and the qualified professionals responsible for the project. Our role is to make sure the right questions are raised while the scope and budget can still be adjusted, not after plans are already in review or equipment has been ordered.

Knowing what the Energy Code is likely to require before you commit helps protect the budget, makes proposals easier to compare, and reduces avoidable permit and construction delays.

Plan first. Understand the scope and numbers. Make informed decisions. Build with clarity.

Your project. Your scope. Your decisions.

Official California resources

• 2025 Building Energy Efficiency Standards
• 2025 Single-Family Residential Compliance Manual
• California Energy Code Climate Zone Tool
• 2025 Single-Family Compliance Forms

This article provides general planning information and is not a project-specific code determination. The adopted code, approved construction documents, and authority having jurisdiction control.