01Key facts / TL;DR
Yes, conditioned additions typically need Energy Code compliance documentation for permit.
It depends which prescriptive or performance path fits the size and actual scope.
No, addition-alone and existing-plus-addition models are not interchangeable shortcuts.
It depends whether a conversion creates new conditioned area even without a larger footprint.
02Answer the need question before choosing the model
An addition is not just a contractor’s label for extra construction. For energy purposes, identify whether conditioned floor area and volume increase and how the proposed space relates to the existing building. A new bedroom, enclosed living area and a conversion can involve different existing conditions. An unconditioned structure is not automatically treated like a conditioned home addition, and this page does not grant it an exemption.
For a typical conditioned single-family addition, plan for applicable Part 6 design documentation. That does not mean every case requires the same full-house performance model. The CEC provides addition pathways and certificate families; size, system connections and changes to existing components can affect the approach. Have the preparer and AHJ identify the applicable path using the actual drawings.
The first paid task may be a scope decision or preliminary option study rather than final permit production. Make that distinction explicit. A report that assumes the wrong existing boundary can be unhelpful even if its inputs produce a favorable result. Start with the building and work, not the model option that appears easiest.
03Addition scope checklist
Separate these quantities and decisions before requesting final documentation:
- +Added conditioned area and volume: show dimensions and boundaries on proposed plans, not only a cover-sheet total or the property’s listing area.
- +Existing retained space: identify what remains untouched and provide supported conditions where the chosen approach needs them. Unknown insulation is not automatically a favorable assumed value.
- +Existing altered components: mark windows, walls, roofs and equipment changed outside the addition. An addition report does not silently resolve every separate alteration.
- +Systems served: show whether equipment serves only the addition or also existing rooms; identify new, extended, replaced and retained systems and the responsible designer.
- +Application/classification: provide the recorded permit date, reviewing agency, dwelling count and whether the new space is an ADU, another unit or part of the original dwelling.
04Addition-alone versus existing-plus-addition: a scoping choice
Addition-alone analysis focuses on the applicable new-work scope. Existing-plus-addition analysis includes a broader existing-building boundary under the relevant method. Neither label permits unsupported existing conditions or the omission of required measures. The appropriate choice follows project scope, the applicable pathway and available evidence.
This intent guide deliberately does not reproduce the detailed modeling comparison. Use the linked technical guide to understand how boundaries affect inputs and design decisions. Then ask the preparer which path is supported for this permit and what existing information it needs. If a broader option study is requested, keep it separate from an assumed permit requirement.
Size provisions and exceptions can matter, but a number from an older form or a different city is not a universal waiver. Confirm the edition-specific requirements and local layer before relying on a threshold. A small conditioned addition is not automatically outside the Energy Code.
Detailed addition-alone versus existing-plus-addition guideEnergy-modeling service
05Worked decision: a bedroom extension and new windows
ILLUSTRATIVE ONLY: a homeowner proposes a 450 sq ft conditioned bedroom addition and replaces some windows in the existing house. The architect labels the new area and the separate window alterations. The mechanical designer identifies which spaces the proposed equipment serves. The applicant records the application date and obtains direction on unresolved scope questions.
The preparer determines the supported addition approach and identifies separate altered-component documentation where applicable. The team does not treat 450 sq ft as a statewide exemption or presume that the addition’s model covers every existing-house change. A broader comparison can be discussed if it serves a defined design question, but no invented pass/fail result is supplied.
The final schedules and report must describe the same window and equipment choices. If the owner later expands the addition or changes the HVAC scope, the preparer reviews the affected documentation instead of reusing the earlier certificate unchanged. A permit package is specific to its coordinated revision.
06Forms, date and field verification
The 2025 California Energy Code applies to building-permit applications on or after January 1, 2026. Confirm the AHJ-recorded date and treatment of amendments or refiling; the addition’s drawing date and construction start do not decide the edition. Use software and forms appropriate to that basis.
Where the single-family family applies, CF1R records design compliance. The CEC catalog distinguishes addition forms and applicable registration conditions. Contractors complete applicable CF2R; qualified ECC-Raters complete required CF3R verification. ECC is current terminology; older-cycle HERS records retain their context. Not every addition has the same verification measures, and preparing CF1R is not performing those tests.
If the proposed addition creates a separate dwelling or affects a multifamily building, confirm classification before assuming the single-family sequence. Unit count, common systems and existing conditioning matter. CF1R is not a universal certificate for every space described as residential.
07What to send for an addition decision
Send dimensioned existing/proposed plans, sections, elevations, opening schedules with U-factor/SHGC, assemblies/insulation and affected equipment information. Identify retained versus new conditions and who can resolve unknowns. Include application history, prior accepted reports and any complete correction letter. A sketch can support a preliminary conversation but is not automatically enough for final output.
The additions service explains production deliverables after scope is agreed. This guide answers why documentation is usually needed and which questions should come first. It does not provide architectural/mechanical design, establish concealed conditions or control plan-check timing. Ask the AHJ about any claimed exception rather than treating a generic website answer as approval.
Additions/remodels serviceExisting additions/alterations guide
08Six addition questions
Does every conditioned bedroom addition need consideration under Part 6?
Typically yes. Identify the actual new conditioned area, altered existing components and application basis, then determine the applicable documents. Do not assume a small floor area is a universal exemption.
Must the energy model include the entire existing house?
Not automatically. Addition-alone and broader existing-plus-addition approaches have different boundaries and evidence needs. The project scope and applicable method determine the supported path.
Can a conversion count as an addition without new outside walls?
Yes, converting unconditioned space can increase conditioned floor area/volume. Document prior conditioning and proposed use. Do not classify the energy scope solely from whether the footprint grows.
Does the addition report cover replacement windows elsewhere?
Do not assume so. Mark those changes separately and ask which altered-component documentation or coordinated analysis applies. The report must represent its actual boundary and work.
What if one HVAC system will serve old and new rooms?
Show the served areas and supported equipment/distribution design. The responsible designer and preparer must coordinate system and model boundaries; the equipment’s location alone does not settle them.
Does a registered CF1R finish construction verification?
No. Design registration, installer records and required ECC verification are distinct stages. Confirm applicable measures and participants before affected construction is concealed.
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 remodel?Do I need Title 24 for adu?Do I need Title 24 for windows?Confirm the application’s code editionWhat to send for an energy reviewCF1R versus installation/verification recordsSee published PricingGet a Quote / upload plans