When Will I Need Title 24 Calculations?

Call (626) 365-1518 | Alternative Energy Systems

When Will I Need Title 24 Calculations usually becomes an important question when a California construction project creates new conditioned space, changes the building envelope, replaces regulated equipment, or alters another part of the building that is covered by the California Energy Code.

You may need energy-compliance calculations or related Title 24 documentation when planning:

• A new home
• A new commercial building
• An accessory dwelling unit
• A garage conversion
• A residential addition
• A major remodel
• A multifamily project
• A commercial tenant improvement
• An HVAC replacement or mechanical alteration
• A window or building-envelope alteration
• A water-heating change
• A commercial lighting project

The important distinction is that not every project requires the same type of calculation.

Some projects use a performance-based energy analysis prepared with California Energy Commission-approved compliance software. Others can demonstrate compliance through applicable prescriptive forms or system-specific documentation.

The correct approach depends on:

• Building type
• Project scope
• Climate zone
• Existing conditions
• Systems being changed
• Selected compliance method

Alternative Energy Systems brings more than 30 years of California energy-compliance experience to residential, multifamily, mixed-use, and commercial construction.

Call (626) 365-1518 if you have plans and want to determine what calculations or compliance documentation your project will need.

The First Trigger Is Usually New Construction or a Change to Energy-Regulated Work

California’s Building Energy Efficiency Standards apply to applicable newly constructed buildings, additions, and alterations.

That means Title 24 can become relevant long before construction begins.

The need for calculations is often triggered when the proposed work affects:

• Conditioned floor area
• Exterior walls
• Roof or ceiling assemblies
• Floors over unconditioned spaces
• Insulation
• Windows or glazed doors
• Heating and cooling systems
• Duct systems
• Ventilation
• Water heating
• Commercial lighting
• Lighting controls

The earlier these components enter the project, the earlier it can make sense to evaluate Title 24 requirements.

When Should I Start Thinking About Title 24 Calculations?

Ideally, energy compliance should be considered while the plans are still being developed rather than immediately before permit submission.

Early calculations can reveal whether the design needs clarification involving:

• Window performance
• Insulation assemblies
• Roof construction
• HVAC efficiency
• Duct locations
• Water heating
• Commercial lighting

Discovering an issue while the plans are still editable can be much easier than discovering it after specifications have been finalized or products have already been ordered.

You Do Not Always Need to Wait Until the Plans Are 100% Finished

AES can often begin reviewing a developing project before every specification has been finalized.

An early review can identify:

• What information is already sufficient
• What information is missing
• Which systems need to be selected
• Which plan details need clarification
• Which decisions may affect the energy analysis

Final calculations still require enough information to accurately describe the proposed building.

The goal is to start early enough to identify problems without finalizing a report around assumptions that will immediately change.

When Will I Need Title 24 Calculations for a New Home?

New residential construction is subject to applicable California Energy Code requirements.

Depending on the compliance method, a new home can require analysis of:

• Building orientation
• Conditioned floor area
• California climate zone
• Exterior walls
• Roof and ceiling assemblies
• Floors
• Insulation
• Window quantity and size
• Window U-factor
• Solar heat gain coefficient
• HVAC systems
• Ducts
• Ventilation
• Water heating
• Other applicable energy measures

If the performance compliance method is used, approved energy-modeling software evaluates the proposed building against the applicable standard design.

New residential construction is therefore one of the clearest situations where energy-compliance planning should begin before permit submission.

When Will I Need Title 24 Calculations for an ADU?

ADUs commonly trigger Title 24 requirements because they create or convert residential living space.

The exact analysis depends on whether the ADU is:

• A newly constructed detached ADU
• An attached ADU
• A garage conversion
• A conversion of another existing space

A new detached ADU may need to be analyzed as a complete new residential structure.

An attached ADU or conversion can require careful separation of existing and proposed construction.

Relevant information may include:

• Conditioned floor area
• Walls
• Roof construction
• Insulation
• Windows
• HVAC
• Ventilation
• Water heating

For more project-specific information, review ADU Title 24.

When Will I Need Title 24 Calculations for a Garage Conversion?

A garage conversion commonly requires energy-compliance review because the project changes space that may have originally been unconditioned into conditioned living space.

That change can introduce requirements for:

• Exterior wall insulation
• Ceiling or roof insulation
• Floor conditions
• Windows
• Exterior doors
• Heating and cooling
• Ventilation
• Water heating when applicable

The fact that the existing garage already has walls and a roof does not automatically mean those assemblies satisfy the requirements for new conditioned living space.

When Will I Need Title 24 Calculations for an Addition?

A residential addition creates new building area that can affect energy compliance.

Examples include:

• Bedroom additions
• Family-room additions
• Kitchen expansions
• Primary-suite additions
• Second-story additions
• Expanded living areas

The new work can involve:

• New conditioned floor area
• New exterior walls
• New roof or ceiling assemblies
• New windows
• New insulation
• Additional heating and cooling loads
• New or extended ductwork

An addition may use an applicable prescriptive compliance path or a performance approach depending on the project.

Does Every Addition Need a Full Performance Calculation?

No.

This is an important distinction.

California provides prescriptive compliance options for qualifying additions.

Some additions can use applicable Certificate of Compliance forms rather than a complete whole-building performance model.

Other projects may benefit from or require performance analysis because of their size, design, glazing, equipment, or selected compliance strategy.

The project should be reviewed before assuming either that a full model is mandatory or that calculations are unnecessary.

When Will I Need Title 24 Calculations During a Remodel?

The word “remodel” alone does not determine the requirement.

A cosmetic project can be very different from an alteration that changes energy-regulated components.

Energy compliance can become relevant when the remodel changes:

• Windows
• Exterior doors
• Exterior walls
• Insulation
• Roof assemblies
• HVAC equipment
• Duct systems
• Water heating
• Commercial lighting

A limited alteration may use specific prescriptive forms rather than a complete performance calculation.

A more extensive remodel can require broader analysis.

When Will Window Changes Trigger Title 24 Requirements?

Windows can affect energy performance because the Energy Code regulates applicable fenestration characteristics.

Relevant values can include:

• U-factor
• Solar heat gain coefficient
• Window area
• Window orientation

The documentation needed depends on whether the window work is part of:

• New construction
• An addition
• A major remodel
• A more limited alteration

A stand-alone window alteration may not need the same performance model as an entire new house, but applicable Energy Code requirements can still apply.

When Will Insulation Changes Matter?

Changing the building envelope can trigger applicable requirements for:

• Exterior walls
• Roofs
• Ceilings
• Attics
• Floors

When those assemblies are part of a project being analyzed, the insulation values need to be represented accurately.

This becomes particularly important during additions, conversions, major remodels, or performance-based compliance.

When Will Roofing Work Affect Title 24?

Roof alterations can have Energy Code requirements depending on:

• Building type
• Roof construction
• Climate zone
• Roofing characteristics
• Scope of the alteration

Some roofing projects can involve applicable cool-roof or envelope provisions without requiring a complete whole-building performance calculation.

The roof scope should be evaluated before assuming no Title 24 documentation is involved.

When Will I Need Calculations Because of HVAC Work?

HVAC work can trigger energy-compliance requirements even when no building addition is being constructed.

Mechanical alterations can involve:

• Equipment type
• Heating efficiency
• Cooling efficiency
• Heat-pump systems
• Duct systems
• Controls
• Airflow
• Applicable field verification

Some HVAC projects use dedicated alteration forms rather than a full building energy model.

If mechanical equipment is being changed as part of a larger addition or remodel, it can also become an input in the broader project analysis.

When Will Duct Changes Matter?

Ductwork can affect energy performance and applicable verification requirements.

A project may need to address:

• Duct location
• Duct insulation
• Duct sealing
• Airflow
• Extension of existing duct systems

When ducts are added, moved, replaced, or extended, the mechanical scope should be evaluated for applicable Title 24 requirements.

When Will Water-Heating Changes Trigger Energy Requirements?

Water heating is a significant regulated energy use.

A project can involve requirements related to:

• Equipment type
• Energy source
• Efficiency
• Heat-pump water heaters
• Central systems
• Individual systems
• Hot-water distribution

A simple equipment alteration can use different documentation from a new building or major remodel.

If water heating is part of a broader performance analysis, the proposed system needs to be represented accurately.

When Will I Need Title 24 Calculations for a Multifamily Building?

Multifamily construction has dedicated Energy Code requirements.

Calculations or compliance documentation can become necessary for:

• New apartment buildings
• New multifamily developments
• Multifamily additions
• Apartment alterations
• Common-area improvements
• Mechanical-system changes
• Water-heating changes
• Lighting alterations

Multifamily buildings should be classified correctly because their compliance requirements differ from both detached single-family homes and ordinary nonresidential buildings.

When Will I Need Title 24 Calculations for a New Commercial Building?

New nonresidential construction is subject to applicable Energy Code requirements.

Depending on the project, the analysis can involve:

• Building envelope
• Windows and storefront glazing
• Mechanical systems
• Ventilation
• Service water heating
• Interior lighting
• Exterior lighting
• Lighting controls
• Other regulated systems

A project can use an applicable prescriptive or performance compliance method.

Performance compliance for the current Energy Code must use California Energy Commission-approved software.

When Will I Need Title 24 Calculations for a Tenant Improvement?

A commercial tenant improvement can trigger energy requirements even though the building already exists.

Projects can include:

• Office improvements
• Retail build-outs
• Restaurant renovations
• Medical offices
• Service-business spaces
• Warehouse office improvements

The tenant improvement may change:

• Lighting
• Lighting controls
• HVAC equipment
• Ventilation
• Water heating
• Storefront glazing

The previous energy documentation for the shell building should not automatically be assumed to cover the new tenant work.

When Will Commercial Lighting Require Title 24 Documentation?

Commercial lighting alterations can trigger Energy Code requirements.

Depending on the scope, the project may need documentation involving:

• Fixture types
• Fixture quantities
• Lighting power
• Occupancy controls
• Automatic shutoff controls
• Daylighting controls
• Exterior lighting

Lighting-only work does not necessarily require the same whole-building model as new construction.

Applicable nonresidential lighting documentation may still be required.

For professional commercial assistance, review Title 24 compliance services.

How Do I Know Whether I Need Prescriptive or Performance Calculations?

California provides both prescriptive and performance compliance methods.

Prescriptive Compliance

Prescriptive compliance follows applicable requirements established for the building components and systems included in the project.

Depending on the scope, those requirements can address:

• Insulation
• Windows
• Roofs
• HVAC systems
• Water heating
• Lighting
• Other applicable components

Performance Compliance

Performance compliance uses approved computer modeling to evaluate the proposed design against the applicable standard design or energy budget.

This approach can allow qualifying design tradeoffs and may be useful when the building does not follow a straightforward prescriptive configuration.

The project should be evaluated before choosing the compliance approach.

When Will Performance Calculations Be Especially Useful?

Performance modeling can be particularly useful when the project involves:

• Large amounts of glazing
• Unusual building geometry
• Multiple envelope assemblies
• Custom architectural features
• Design tradeoffs
• Complex HVAC systems
• A project that does not fit a simple prescriptive approach

The analysis allows different energy measures to be evaluated together.

For example, a design with more glazing may potentially compensate through other qualifying efficiency improvements.

When Will Prescriptive Forms Be Enough?

Some additions and alterations can demonstrate compliance using applicable prescriptive forms rather than a complete performance model.

The California Energy Commission provides dedicated forms for various types of:

• Residential additions
• Residential alterations
• Space-conditioning alterations
• Other eligible scopes

The exact form depends on the project and whether separate field verification is required.

Prescriptive compliance is still Title 24 compliance.

It should not be confused with an exemption.

Will I Need Calculations Just Because I Need a Building Permit?

Not necessarily in the same form for every project.

A building permit may require:

• A performance energy report
• Prescriptive forms
• Mechanical compliance documents
• Lighting forms
• Other project-specific energy documentation

The building permit itself does not automatically establish that a full whole-building performance model is required.

The construction scope determines the applicable energy documentation.

Can Title 24 Apply Even if I Do Not Need a Full Calculation?

Yes.

This is one of the most important points to understand.

A project can be subject to California’s Energy Code even when a full performance calculation is unnecessary.

For example, an alteration may need to satisfy:

• Mandatory requirements
• Prescriptive requirements
• Equipment requirements
• Installation requirements
• Verification requirements

using project-specific forms instead of a whole-building energy model.

When Might I Not Need a Full Title 24 Calculation?

Depending on the project, a full performance model may not be necessary for:

• Certain limited alterations
• Qualifying prescriptive additions
• Some HVAC-only projects
• Some lighting-only projects
• Some envelope alterations
• True repair work that falls outside applicable alteration requirements

The actual scope should be reviewed before an exemption or limited compliance path is assumed.

A Repair and an Alteration Are Not Always the Same Thing

Calling work a repair does not necessarily determine its Energy Code treatment.

Replacing a regulated component can sometimes constitute an alteration.

Examples can include:

• Window replacement
• HVAC replacement
• Duct replacement
• Water-heater replacement
• Roofing work

The actual work being performed determines which provisions apply.

When Should I Contact AES During the Design Process?

A good time to begin is when the basic building design is developed enough to identify:

• Project scope
• Building size
• Floor plans
• Exterior elevations
• Roof configuration
• Windows
• Envelope assemblies
• Proposed mechanical systems

The plans do not necessarily need every final product model at the first review.

Starting before the permit package is completely finished gives AES an opportunity to identify missing information before it creates a last-minute problem.

Why Waiting Until Permit Submission Can Create Problems

If energy analysis begins only after the architectural plans are considered complete, a compliance issue can force revisions to work that has already been coordinated.

Potential changes can involve:

• Window specifications
• Insulation
• Roof details
• HVAC equipment
• Mechanical notes
• Commercial lighting

Beginning earlier can give the architect, owner, contractor, and energy consultant more flexibility to resolve those questions.

When Do Calculations Need to Be Revised?

Title 24 calculations should be reviewed when the project changes an energy-related feature represented in the existing analysis.

Examples include:

• Increasing or decreasing conditioned floor area
• Changing room configuration
• Adding or removing windows
• Changing window performance
• Changing insulation
• Changing the roof assembly
• Changing HVAC equipment
• Changing duct locations
• Changing ventilation
• Changing water heating
• Changing commercial lighting

The significance of the revision depends on the extent of the design change.

Will I Need New Calculations After Building Department Corrections?

Sometimes.

A building-department correction may simply ask for clarification.

Another correction may identify a design conflict requiring a recalculation.

Energy-related comments can involve:

• Incorrect or missing forms
• Incorrect climate zone
• Floor-area discrepancies
• Window discrepancies
• Insulation discrepancies
• Mechanical changes
• Lighting-control information
• Differences between the report and plans

Send AES the complete correction notice and latest plans so the actual issue can be evaluated.

Will I Need New Calculations if My Contractor Changes Equipment?

Potentially.

A product substitution should be reviewed when it changes a value or system represented in the energy documentation.

Examples include:

• A different HVAC unit
• Different windows
• A different water heater
• A different insulation assembly
• A changed roof specification

A replacement product that performs the same basic function is not automatically equivalent for energy-compliance purposes.

Will I Need New Calculations if My Plans Change After Permit Approval?

A significant post-permit design change can require revised calculations and approval by the authority having jurisdiction.

The project should continue to correspond to the approved energy documentation during construction.

Notify the project team before making substantial changes to:

• Windows
• Insulation
• HVAC equipment
• Ductwork
• Water heating
• Commercial lighting
• Other modeled building features

What Energy Code Applies to Projects Now?

For applicable permit applications filed on or after January 1, 2026, the current statewide standard is the 2025 California Building Energy Efficiency Standards.

When the performance compliance method is used, the project must use California Energy Commission-approved software for the applicable 2025 Energy Code building category and project scope.

For official information, review the California Energy Commission 2025 Energy Code Compliance Software information.

The Permit Date Can Determine Which Code Cycle Applies

California updates the Energy Code on a three-year cycle.

The applicable code edition can depend on the permit circumstances.

Projects beginning under one code cycle should not automatically be converted to another simply because the calendar year changes.

If a project spans a code transition, confirm the applicable code edition with the building department and provide AES with any permit information already available.

What Should I Send Before Requesting Calculations?

The exact information depends on the project.

Useful documents can include:

• Floor plans
• Exterior elevations
• Building sections
• Roof plans
• Window schedules
• Window-performance information
• Insulation details
• HVAC specifications
• Duct-location information
• Ventilation information
• Water-heating specifications
• Commercial lighting plans when applicable
• Commercial lighting-control information when applicable
• Existing energy documentation
• Building-department correction comments

Not every project requires every item.

AES can review the available information and identify what is still needed.

Before sending files, review what AES will need from you.

What Happens After I Send My Plans?

The process generally begins by identifying the actual scope of work.

1. Determine the Project Type

AES identifies whether the project involves new construction, an ADU, addition, conversion, remodel, multifamily project, commercial tenant improvement, or another applicable scope.

2. Determine the Applicable Compliance Method

The project is reviewed to determine whether prescriptive documentation, performance calculations, or another applicable compliance path is appropriate.

3. Review the Plans and Specifications

Energy-related features of the proposed building are identified.

4. Identify Missing Information

AES can identify unanswered questions involving windows, insulation, mechanical systems, water heating, or other required project information.

5. Prepare the Applicable Analysis

The energy analysis or prescriptive documentation is prepared according to the project.

6. Coordinate the Results With the Plans

The applicable energy measures should agree with the construction documents before permit submission.

For more information about the technical process, review Title 24 energy calculations.

Why Choose Alternative Energy Systems?

Alternative Energy Systems provides Title 24 energy calculations, compliance documentation, revisions, and energy-related plan-check support throughout California.

AES brings more than 30 years of California energy-compliance experience to:

• New homes
• ADUs
• Garage conversions
• Additions
• Residential remodels
• Multifamily buildings
• Mixed-use projects
• Commercial construction
• Office tenant improvements
• Retail projects
• Restaurant projects
• Warehouse alterations
• HVAC projects
• Commercial lighting projects
• Energy-related plan-check corrections

AES evaluates the actual construction scope rather than assuming every project needs the same type of report.

Learn more through the About Us page or review company background on the clients page.

Find Out When Your Project Will Need Title 24 Calculations

Call (626) 365-1518 | Alternative Energy Systems

The best answer to When Will I Need Title 24 Calculations depends on what you plan to build or change.

Energy compliance commonly becomes relevant when your project involves:

• New conditioned space
• A new residential or commercial building
• An ADU
• A garage conversion
• An addition
• Energy-related remodeling
• Window or envelope changes
• HVAC or duct changes
• Water-heating changes
• Commercial lighting
• A multifamily project
• A commercial tenant improvement

The project may need a complete performance calculation, prescriptive compliance documentation, system-specific forms, or a combination of requirements.

The most effective time to determine that is before permit submission and before major energy-related products are ordered.

Alternative Energy Systems can review your plans and determine what information is needed for the applicable compliance path.

Call (626) 365-1518 or begin through the contact page.

When service and payment have already been arranged, payment can be completed through the AES payment page.

Frequently Asked Questions: When Will I Need Title 24 Calculations?

When Will I Need Title 24 Calculations?

You can need Title 24 calculations or related energy-compliance documentation when a California project involves applicable new construction, additions, alterations, conversions, or regulated energy-related building systems.

Do I need calculations for a new house?

New residential construction is subject to applicable Energy Code requirements and requires the appropriate compliance documentation.

Do I need calculations for an ADU?

Applicable ADUs require energy-compliance documentation. The exact method depends on whether the ADU is new, attached, detached, or created from existing space.

Do I need calculations for a garage conversion?

Garage conversions commonly require energy-compliance review because previously unconditioned space is being converted into conditioned living space.

Do I need calculations for an addition?

Applicable additions must comply with the Energy Code. Depending on the project, compliance may use a prescriptive or performance method.

Does a small addition require a full performance model?

Not necessarily. Some qualifying additions can use applicable prescriptive compliance forms.

Do I need calculations for a remodel?

Possibly. Remodels that alter windows, envelope assemblies, HVAC, ducts, water heating, roofing, commercial lighting, or other regulated systems can trigger applicable requirements.

Do replacement windows trigger Title 24?

Applicable window alterations can be subject to Energy Code requirements even when a complete whole-building performance model is unnecessary.

Does new insulation trigger Title 24?

Alterations to regulated envelope assemblies can be subject to applicable insulation and energy requirements.

Does reroofing trigger Title 24?

Roof alterations can have Energy Code requirements depending on building type, roof characteristics, climate zone, and project scope.

Will I need calculations when replacing HVAC equipment?

Mechanical alterations can trigger equipment, duct, control, and verification requirements. Some HVAC projects use specific alteration forms rather than a complete building model.

Will ductwork trigger Title 24?

Applicable duct additions or alterations can trigger requirements involving sealing, insulation, airflow, location, or field verification.

Will replacing a water heater trigger Title 24?

Applicable water-heating alterations can have Energy Code requirements depending on building type, equipment, and project scope.

Will a commercial tenant improvement need Title 24 calculations?

It can. Lighting, HVAC, ventilation, water heating, glazing, and other altered systems can trigger nonresidential requirements.

Will commercial lighting require Title 24 documentation?

Applicable commercial lighting alterations can require lighting-power and control documentation even without a whole-building performance model.

Will multifamily construction require Title 24 calculations?

Applicable new multifamily construction, additions, and alterations are subject to dedicated multifamily Energy Code requirements.

Does every building permit require a full Title 24 calculation?

No. Some permit scopes use prescriptive or system-specific compliance forms instead.

Can Title 24 apply even when I do not need a full energy model?

Yes. Mandatory, prescriptive, installation, or verification requirements can still apply.

What is prescriptive compliance?

Prescriptive compliance follows applicable component and system requirements established by the Energy Code.

What is performance compliance?

Performance compliance uses approved computer modeling to compare the proposed building with the applicable standard design or energy budget.

When is performance modeling useful?

It can be useful for new construction, complex projects, unusual glazing, design tradeoffs, or projects that do not fit a straightforward prescriptive approach.

When should I order Title 24 calculations?

It is generally best to begin energy review before the permit plans are considered completely final and before major energy-related products are purchased.

Can calculations begin before my plans are finished?

Preliminary review can begin with available drawings, but final calculations require enough information to accurately represent the proposed project.

Will I need revised calculations if my plans change?

Potentially. Changes to floor area, windows, insulation, roofing, HVAC, ducts, water heating, lighting, or other analyzed features can require revision.

Will I need revised calculations after plan-check corrections?

Sometimes. It depends on whether the correction requires clarification or an actual change to the analyzed project.

Will changing HVAC equipment require new calculations?

The report should be reviewed when substituted equipment changes an energy characteristic used in the existing analysis.

What Energy Code applies now?

For applicable permit applications filed on or after January 1, 2026, California uses the 2025 Building Energy Efficiency Standards.

Do performance calculations require approved software?

Yes. Performance compliance must use software approved by the California Energy Commission for the applicable code cycle, building type, and project scope.

What should I send AES first?

Current floor plans, elevations, sections, roof plans, window information, insulation details, HVAC specifications, water-heating information, commercial lighting information when applicable, and existing correction comments are useful starting documents.

How do I find out exactly what my project needs?

Call Alternative Energy Systems at (626) 365-1518 and provide the current plans and proposed construction scope for review.