ADU Questions · 2026
ADU Title 24 Energy Requirements
Title 24 is California’s statewide energy code, and it sets efficiency standards for insulation, windows, HVAC equipment, water heating, and lighting on new construction, including new ADUs. It is separate from, but related to, California’s rooftop solar mandate, which is its own narrower requirement layered on top for certain new construction.
The short version: Title 24 governs how energy-efficient your ADU’s building envelope and mechanical systems have to be. It applies to new construction ADUs, and a related but distinct solar requirement may also apply depending on your ADU’s size, type, and roof conditions. Your plan set will spell out exactly what applies to your build.
What Title 24 actually regulates
Title 24, Part 6 of the California Building Standards Code, is the state’s energy code. Its goal is straightforward: reduce how much energy a building uses to heat, cool, light, and run itself, year after year.
For a new ADU, that shows up in a handful of concrete places:
| Building system | What Title 24 addresses |
|---|---|
| Insulation and building envelope | How well walls, ceilings, and the roof hold conditioned air in |
| Windows and doors | Efficiency ratings that limit heat gain and heat loss |
| HVAC equipment | Minimum efficiency standards for heating and cooling systems |
| Water heating | Efficiency requirements for the water heater |
| Lighting | Efficient fixtures and controls |
| Rooftop solar | A related, separate mandate for certain new construction, covered below |
None of this is unique to ADUs. It is the same energy code that applies to new single-family homes across the state. An ADU built as new construction gets held to the same bar as any other new home.
Title 24 energy efficiency versus the solar mandate
These two pieces get talked about together so often that people assume they are the same rule. They are not.
The insulation, window, and HVAC efficiency standards are about how the building itself performs, how well it keeps conditioned air where it belongs and how efficiently its systems run. These standards apply broadly to newly constructed ADUs, the same way they apply to any new single-family home.
Rooftop solar is a separate, narrower piece. Generally, newly constructed detached ADUs where the permit application was submitted on or after January 1, 2020 must include solar panels, similar to new single-family homes. But there are real exemptions:
- A small-ADU exemption, which in practice often exempts smaller detached ADUs, depending on the calculated solar requirement for your specific home.
- A limited-solar-access exemption, for lots where very little usable roof area actually gets enough sun.
- Attached ADUs and conversions, meaning units built within an existing structure’s footprint (a garage, basement, attic, or an addition), which are treated as alterations rather than new construction and are generally not subject to the solar requirement at all.
Whether solar applies to your specific ADU depends on its size, your local climate zone, and your roof conditions. That is not a one-size-fits-all answer, and it is one of the things your plan set confirms in detail.
What this means while you are planning
If you are building a new detached ADU, budget for a home that meets modern efficiency standards on insulation, windows, and HVAC as a baseline, and confirm early whether the solar piece applies to your specific footprint and roof. If you are converting an existing structure, like a garage conversion, the solar mandate generally will not apply, though the project still moves through the same ministerial permit process as any other ADU.
Either way, Title 24 compliance is not something you calculate yourself. It is built into your plan set and reviewed as part of your permit, alongside the setback, height, and parking rules covered in our overview of California ADU laws.
How Framework First handles Title 24
This is one of the clearer advantages of building in a factory instead of on a site. Roughly 97% of every Framework First home is built in our Salinas facility, then crane-delivered to the property in a single day. Because every home comes off the same production line to the same specifications, insulation, windows, and mechanical systems are installed the same way every time, rather than varying by crew, weather, or site conditions the way they can on a stick-built job.
That consistency matters for energy code compliance specifically. A factory environment does not have the same day-to-day variability a site-built crew deals with, so the building envelope and systems that Title 24 cares about get built the same way on every unit. Our all-inclusive pricing, which runs $180,000 to $557,000 across our 14 models and carries a permitting budget confirmed exactly for your address in the feasibility study, already accounts for a design and build process that meets these requirements as part of the plan, not as an add-on. You can see how this compares to site-built construction in our prefab versus site-built ADU guide.
Frequently asked questions
Does Title 24 apply to every ADU?
The energy efficiency standards (insulation, windows, HVAC) generally apply to newly constructed ADUs, the same as any new single-family home. The separate solar mandate is narrower and depends on whether your ADU is new construction, its size, your climate zone, and your roof conditions, with real exemptions for smaller units and for attached ADUs or conversions.
Is the solar requirement the same as Title 24?
No. Solar is a related but distinct piece layered on top of the broader Title 24 energy code. Title 24 as a whole covers insulation, windows, HVAC, water heating, and lighting efficiency. The solar mandate is a separate rule that applies to some, but not all, newly constructed detached ADUs.
Does a garage conversion need solar panels?
Generally, no. Attached ADUs and conversions built within an existing structure’s footprint are treated as alterations rather than new construction, and are generally not subject to the solar requirement. Confirm your specific situation with your plan set, since exact applicability depends on your project’s details.
How do I find out if my ADU is exempt from solar?
The small-ADU exemption and the limited-solar-access exemption both depend on calculations specific to your home’s size, roof area, and climate zone. Your plan set will confirm exactly which exemptions, if any, apply. This is exactly the kind of detail we walk through during a feasibility study.
Does meeting Title 24 cost extra on top of the sticker price?
With Framework First, meeting Title 24 itself is not a separate line item. It is built into the standard design and build process, the same as the foundation, the factory build, delivery, utility hookups, appliances, and final inspection, and every price already carries a permitting budget for that work. What can move the number is the permit itself, since exact permit costs are set by your city or county and get confirmed for your address in the feasibility study.
See which of our 14 models fits your lot and budget. Start with a feasibility study or browse our models to get started.