01Key facts / TL;DR
Yes, a newly constructed detached ADU generally follows the new single-family Energy Code path.
Yes, creating conditioned space from an unconditioned garage can trigger addition requirements even without expanding the footprint.
It depends which components change when already-conditioned space becomes an ADU or JADU.
No, an ADU planning approval or a small unit size does not itself waive Part 6 documentation.
Garage conversion matrix
ADU, habitable accessory space or storage
A reference for how intended use shapes which energy documents may apply. No row is a universal form list, a requirement for a full model, or a permit exemption.
| Scenario | Documents, scope and what to send |
|---|---|
| Garage to ADUA separate dwelling unit | Documents: Possibly a CF1R, depending on project classification and regulated scope. Not automatically a full model. What decides it: Classification, conditioning, permit application date and the AHJ. Send: Floor plan, elevations, window schedule, proposed HVAC and water heating. |
| Habitable accessory spaceNot a separate dwelling | Documents: Possibly a CF1R or alteration documentation, depending on how the space is classified. What decides it: Whether the space becomes conditioned and how the AHJ classifies it. Send: Floor plan, wall, ceiling and window changes, and any conditioning equipment. |
| Unconditioned storageParking, tools or storage | Documents: Not an automatic exemption. Lighting or other altered scope in the permit may still need documentation. What decides it: Whether it stays unconditioned and what the permit actually alters. Send: Floor plan and any lighting or electrical scope. |
Educational information, not legal advice or a compliance determination. Confirm requirements and the applicable code cycle for your permit application date with your building department (AHJ).
02The planning label is not the energy classification
ADU is a useful housing description, but the energy decision needs the physical scope and existing conditions. The CEC’s 2025 ADU FAQs distinguish newly constructed detached buildings, additions and alterations. Those distinctions help determine the applicable requirements before a preparer chooses forms or a model boundary.
A new detached structure generally follows the new single-family path. An attached ADU or conversion of unconditioned space can be an addition for energy purposes. Conversion of already-conditioned space can instead be an alteration, with requirements triggered by changed regulated components. Do not treat every garage conversion as the same category or every interior conversion as exempt.
A JADU has an Energy Code definition; the word on a rental listing does not establish compliance treatment. Describe the proposed arrangement, prior conditioning, connections and changed systems. Ask the AHJ and project team to resolve classification questions rather than selecting the certificate that looks shortest.
03A detached/attached/conversion/JADU decision checklist
Use the checklist to define what is being approved—not to determine zoning eligibility.
- +New detached: is this a building that has never been used or occupied, or a conversion of an existing structure? Provide site/building plans, not just a proposed unit area.
- +Attached work: show common walls/floors/ceilings, added conditioned area and how systems connect to the original dwelling. Do not hide a new unit inside an undifferentiated house total.
- +Garage conversion: document previous conditioning and permitted conditions, retained envelope, proposed insulation, new openings and HVAC/hot-water scope. Do not invent existing assembly values.
- +JADU/conditioned conversion: identify existing conditioned boundaries, proposed layout and changed components. A retained floor area can still contain regulated alterations.
- +Mixed work: separate main-house alterations, additions and the new unit; identify dwelling count, systems served and application history for the whole submitted scope.
04Do I need a full model, or another compliance path?
Applicable mandatory requirements remain whether the chosen approach is prescriptive or performance. A new detached ADU can use the appropriate supported approach, while additions/conversions follow the provisions for their classification. A small building is not automatically outside the Energy Code or entitled to a simplified path regardless of design.
Performance modeling can help evaluate supported design options, but it is not the same question as whether energy documentation is required. Before ordering a full model, identify the applicable approach, building boundary and available inputs. Existing-plus-addition analysis should not be selected merely because a different boundary appears to produce a favorable answer.
The detailed ADU guide explains these pathways further. This intent page supplies the first decision and packet to request; the service page explains preparation after scope is agreed. Do not use a neighboring permit’s form set or an old garage report as proof that the current application needs the same records.
Detailed ADU energy-compliance guideADU/garage-conversion serviceEnergy-modeling support
05Worked decision: a new detached unit versus a garage conversion
ILLUSTRATIVE ONLY: compare a proposed 550 sq ft new detached ADU with a 550 sq ft conversion of an existing unconditioned garage. Equal area does not make them the same energy scope. The first is newly constructed; the second involves a conversion to conditioned space that the CEC describes within its addition framing.
The preparer asks for new-building inputs in the first case and supported existing/proposed conditions in the second. The team also checks applicable PV provisions: the CEC distinguishes new detached ADUs from additions and describes exceptions and qualifying new PV. No universal array size, exemption or passing result is inferred from 550 sq ft.
If the garage was already conditioned, the classification question changes again. If its prior use or permit status is unclear, ask the AHJ how to establish the compliance basis. Do not use a photograph of a heater as proof of an accepted conditioned building. The useful output is a documented scope decision before final report production.
06Application record, CF1R and ECC are separate decisions
The 2025 California Energy Code applies to building-permit applications on or after January 1, 2026. Confirm the recorded date; a prior ADU planning conversation, property purchase or drawing date is not automatically the building application date. Ask the AHJ about refiling, legalization or amendments rather than choosing the older edition by preference.
Where the single-family family applies, CF1R records design compliance and must align with plans, equipment and opening schedules. Applicable CF2R are installer records; required CF3R are qualified ECC-Rater verification. ECC is current terminology, with HERS remaining relevant as legacy/older-cycle wording. Report preparation is not the field visit.
Coordinate registration when required by the selected measures and document pathway. Do not assume that any downloaded unregistered PDF is sufficient or that every ADU needs every verification measure. Keep the design, installer and verification responsibilities visible before construction handoff.
CF1R documentation and responsibilitiesCEC single-family forms
07What to send before requesting the ADU quote
Include existing/proposed plans and sections, unit/building boundaries, conditioned area, dwelling count, opening schedules with U-factor/SHGC, assemblies and HVAC/hot-water information. Identify whether equipment is separate, shared, extended or replaced and who supplies its design. Mark provisional selections rather than inventing ratings.
Attach application history, prior reports and complete plan-check comments where applicable. Clearly identify main-house changes so they are not accidentally excluded. Use published residential square-footage/unit-count pricing as the starting point rather than expecting an invented ADU-only menu or a price that includes all testing and agency fees.
08Six ADU decisions
Does an ADU planning approval replace the energy package?
No. Planning entitlement and building-energy documentation are different matters. Identify the actual building work, classification and recorded application date before selecting the applicable design records.
Can a garage conversion be an addition without expanding the building?
Yes. Converting unconditioned space to conditioned space can increase conditioned area/volume. The CEC ADU FAQs explain this framing; document the existing condition and confirm the project basis.
Is a conversion of an already-conditioned room always exempt?
No. It can be an alteration, and changed regulated components can trigger requirements. Identify equipment, lighting, envelope and other work rather than relying only on unchanged floor area.
Does a JADU automatically use a different energy exemption?
No automatic exemption is established here. Use the Energy Code definition, existing conditioning and actual changed scope. Confirm the applicable requirements and documents with the AHJ.
Does every ADU require the same PV installation?
No. The CEC distinguishes newly constructed detached ADUs from additions and describes applicable provisions/exceptions. Do not copy an array size or claim an existing system without reviewing the actual requirements.
Can one house report automatically cover the ADU and all alterations?
Do not assume that. Provide buildings, units, system boundaries and main-house changes for scope review. The package must accurately represent the approved work and applicable form families.
09Choose the next documentation step
Use the published residential/commercial square-footage menu to understand report pricing, then send a scoped request rather than assuming a full model is necessary. Field testing, acceptance testing, registry fees, CALGreen and AHJ permit fees are separate. Intake is not payment, production acceptance or permit approval. This is educational information, not legal advice; confirm the applicable requirements and documentation with the authority having jurisdiction (AHJ).
Start with the Title 24 decision hubDo I need Title 24 for addition?Do I need Title 24 for new construction?Do I need Title 24 for remodel?Confirm the application’s code editionWhat to send for an energy reviewCF1R versus installation/verification recordsSee published PricingGet a Quote / upload plans