Title 24 Requirements in California

What Title 24 Part 6 covers

Title 24 is the California Building Standards Code, and Part 6 within it is the Energy Code. The California Energy Commission updates it every three years. The 2025 edition was adopted by the Commission in September 2024, approved by the Building Standards Commission in December 2024, and applies to buildings whose permit applications are submitted on or after 1 January 2026. It is the code in force today; what changed from 2022 is covered in what changed in the 2025 Energy Code.

Section 100.0 sets the scope. Part 6 applies to buildings of Occupancy Groups A, B, E, F, H, I, L, M, R, S and U that need a building permit, conditioned or not. It regulates the envelope, space conditioning, water heating, pools and spas, solar-ready provisions, lighting, electrical power distribution and signs.

It covers newly constructed buildings, additions and alterations. Repairs are outside it, but replacing a regulated component, such as a water heater or a window, is an alteration. A few buildings are partly or wholly exempt, and whether your own scope needs a report is answered in do I need a Title 24 report.

Three building types, three sets of sections

Beyond the general Sections 100.0 to 110.12, each building type has its own sections.

• Single-family: Group R-3 dwellings of any height, including duplexes, townhouses and ADUs. Sections 150.0 to 150.2.
• Multifamily: Group R-2 buildings other than hotels and motels, Group R-4, and some congregate residences, at any height. Sections 160.0 to 180.4.
• Nonresidential: offices, shops, schools, warehouses, restaurants and the other nonresidential occupancies, plus hotels and motels. Sections 120.0 to 141.1.

A mixed-use building complies part by part, unless one occupancy makes up at least 80 per cent of the conditioned floor area; then its envelope, HVAC and water heating may follow that occupancy's rules.

The three layers: mandatory, prescriptive and performance

Under Section 100.0(e), every newly constructed building must satisfy the mandatory measures, and then either the prescriptive approach or the performance approach.

Mandatory measures apply whichever route is taken. For a single-family home they include minimum insulation of R-15 in 2x4 wood-framed walls and R-21 in 2x6 walls, a maximum area-weighted window U-factor of 0.40, and dwelling ventilation to ASHRAE Standard 62.2 as amended by the code. A design cannot trade its way out of these.

The prescriptive approach is a package of component requirements for the building's climate zone: insulation levels, window performance, equipment types and efficiencies. Each item must be met. Miss one and the design does not comply prescriptively, however well the building performs overall.

The performance approach uses software approved by the Energy Commission to model the proposed design against a standard design built to the prescriptive package. The building complies if its modelled energy use is no greater than that energy budget, measured in long-term system cost and, for new buildings, source energy as well. This is the route that lets a large glazed wall be offset by better insulation or equipment elsewhere. Prescriptive vs performance compliance compares the two.

How climate zone changes the requirements

California is divided into 16 building climate zones, defined in Reference Joint Appendix JA2. The Energy Commission assigns an energy budget to each building type in each zone, and the zone follows the project's location.

• In the single-family package (Table 150.1-A), the maximum window U-factor for most new homes is 0.27 in zones 1 to 5, 11 to 14 and 16, and 0.30 in the rest.
• A whole-house fan is part of the single-family package in zones 8 to 14 only. Cool roof and radiant barrier requirements also vary by zone.
• Nonresidential solar sizing uses capacity factors that differ by zone, in Table 140.10-A.

The same design can therefore comply in one city and fail in the next. California climate zones explains how a zone is assigned.

Single-family homes and ADUs

For single-family homes, the largest 2025 change is a heat pump baseline. Under the prescriptive approach, in every climate zone, the space-conditioning system must be a heat pump. Water heating must be a 240-volt heat pump water heater, a qualifying higher-tier heat pump water heater, or solar water heating with electric backup. The Energy Commission does not mandate a fuel type: a home with gas equipment can still comply, through the performance approach.

• Electric-ready: a gas or propane furnace, water heater, cooktop or clothes dryer needs a dedicated 240-volt circuit or receptacle nearby and reserved panel space, so it can later be replaced with an electric appliance.
• Solar: the prescriptive package requires a PV system on a newly constructed home, sized by formula and capped by the roof area suitable for panels. No system is required where the minimum works out below 1.8 kWdc, and the size may be reduced by 25 per cent when a qualifying battery is installed.
• Battery-ready: a new home with one or two dwelling units and electrical service greater than 125 amps must be wired ready for a future battery, unless a battery is installed.
• Ventilation: whole-dwelling mechanical ventilation rates were revised for 2025, and opening windows does not count as the ventilation method.
• Verification: refrigerant charge verification now applies to heat pumps in all climate zones.

The Energy Code has no separate category for accessory dwelling units. A new detached ADU is a newly constructed building and meets the same requirements as a new house, solar included. An ADU built as an addition, such as a unit over an existing garage, or created inside existing space, follows the additions and alterations rules instead, and PV is not required for additions. See ADU Title 24 reports and residential Title 24 reports.

Multifamily buildings

Multifamily buildings have their own mandatory measures (Section 160.0 onward), prescriptive package (170.2) and performance approach (170.1). For 2025:

• Heat pumps: low-rise buildings with individual water heaters in each dwelling unit now have a heat pump water heater baseline, adding to the heat pump space-heating baseline introduced in 2022.
• Electric-ready: where gas or propane serves space heating, cooking, clothes drying or water heating, including central water heating, a new building must provide the circuits and panel space for an electric replacement.
• Ventilation: requirements were strengthened to improve indoor air quality. See multifamily ventilation requirements.
• Solar and batteries: under the prescriptive package, buildings of up to three habitable storeys need a PV system, and buildings of more than three habitable storeys need PV and battery storage.

Nonresidential buildings

Nonresidential buildings meet the mandatory measures in Sections 120.0 to 130.5, then either the prescriptive requirements in Sections 140.2 to 140.10 or the performance approach in Section 140.1. For 2025:

• Heat pumps: the heat pump baselines for space conditioning extend to more newly constructed nonresidential building types.
• Solar and batteries: the newly constructed building types listed in Table 140.10-A, including offices, retail, schools, warehouses, restaurants, hotels and libraries, need a PV system and battery storage, with exceptions for small systems and limited roof area. For 2025 the list adds assembly buildings such as places of worship and sports and recreation facilities. See commercial solar and battery requirements.
• Electric-ready: newly constructed commercial kitchens must now be electric-ready, unless they are all-electric or in a healthcare facility.
• Envelope: prescriptive roof and wall U-factors are tighter, and a mandatory vestibule requirement applies at public entrances to buildings of Occupancy Groups A, B, E, I and M, with exceptions.
• Mechanical: HVAC efficiency and control requirements are updated, including a new prescriptive requirement to use ASHRAE Guideline 36.
• Existing buildings: a replacement single-zone rooftop unit in an existing retail, school, office or library building must be a heat pump or another high-efficiency option, depending on the climate zone (Table 141.0-E-1). See rooftop unit replacement.

New nonresidential buildings also carry commissioning requirements under Section 120.8, in full from 10,000 square feet of conditioned nonresidential space. See commercial Title 24 reports.

Additions and alterations

For an existing building, the requirements attach to what the project adds or changes, not to the whole building.

• Additions increase conditioned floor area and volume, which includes turning a garage into conditioned space. A single-family addition meets the applicable mandatory measures and either the prescriptive requirements, which for additions over 700 square feet follow the new-home package with modifications, or the performance approach, modelling the addition alone or with the existing house. PV is not required for additions.
• Alterations change the envelope, space conditioning, water heating, lighting or electrical power distribution without adding floor area. Under the prescriptive approach, the altered component and any new equipment serving it must meet the applicable requirements.

Nonresidential additions and alterations follow Section 141.0, and multifamily ones Section 180.0. A change of occupancy brings the requirements for the new occupancy, and a project that strips out all the wallboard, insulation and exterior walls may be classed as new construction. See room additions, remodels and commercial alterations vs new construction.

How compliance is shown

Compliance is documented on standard certificates. The design-stage certificate of compliance is the document submitted for plan check.

• CF1R for single-family homes, duplexes, townhouses and ADUs
• LMCC for multifamily buildings of up to three habitable storeys
• NRCC for nonresidential buildings, hotels and motels, and multifamily buildings of four or more habitable storeys

Later certificates record installation (CF2R, LMCI, NRCI), nonresidential acceptance tests (NRCA) and field verification by an ECC-Rater (CF3R, LMCV, NRCV). Residential projects that rely on field verification register them with an ECC provider data registry such as CHEERS. See Title 24 forms, and for the order in which it all happens, Title 24 compliance in California.

Who enforces it

The Energy Commission writes the standards but does not enforce them project by project. The local enforcement agency does: usually the city or county building department, and for public schools the Division of the State Architect. Under Part 1, Section 10-103(d), it may not issue a permit until it has determined in writing that the design complies with the Part 6 requirements in effect on the date the permit was applied for, and it inspects the work before final sign-off.

Cities and counties may also adopt stricter local standards, if they find them cost effective and the Energy Commission finds they require buildings to use less energy than Part 6 allows. See what is a reach code and who enforces Title 24.

Frequently Asked Questions

Is the 2025 Energy Code in effect now?

Does the 2025 Energy Code ban gas appliances?

Does a new ADU need solar panels?

Which certificate does an apartment building use?

Do Title 24 requirements apply to repairs?