This page is a collection of resources to help you understand the rules and codes that apply when building an ADU in California, technical guidance on how to build greener, energy-efficient, high-performing ADUs, and resources to make ADUs more accessible to you, your family and neighborhood.

Sections include:

ADU Building Rules, Codes & Guidance

State and local guidance on energy and building codes that apply to ADUs
Play Video
For a written summary of the presentation, go here.
2019 Title 24, Part 6 (Energy Code) for ADUs

California Energy Commission (CEC) Energy Specialists Amie Brusseau walks us through a presentation of what components of the 2019 energy code apply to ADUs, from new construction to alterations and additions.

CEC Hotline

For specific technical question, reach out to:

[email protected]

(800) 772-3300

Resources mentioned in the presentation

Energy Code Ace Guide

Two page quick reference on ADU building specifications for Title 24, Part 6 energy code.


Housing and Community Development (HCD) ADU Handbook Guide

Relevant rules from the California HCD for ADUs and JADUs including all zoning districts that allow single-family and multifamily uses, limited exemptions or reductions in impact fees, and reduced parking requirements.


California Energy Center (CEC) Online Resource Center Website

Website that provides Building Energy Efficiency Standards (Energy Code) educational assistance. Resources include fact sheets, energy videos and presentations organized by topic (e.g. water heating, solar, lighting, building envelope and HVAC).

Other Helpful Resources

Guide to Garage Conversions

Simplifies the process and rules that apply to one of the more cost effective types of ADUs.

Symbium Build

Learn instantly if you can have an ADU on your property

Facebook Group: How to ADU

A community of ADU homeowners and builders navigating the process of building an ADU in California.

Green Building Techniques for ADUs

Above and beyond: reach codes for healthy, sustainable homes.

A research report with findings that a reduced home size and/or addition of an ADU is an effective strategy for reducing both energy consumption and material waste, and provides flexibility and adaptability for different family configurations over time.


A practical homeowner and developer guide with efficient electric alternatives to replace existing gas appliances. Helpful inspiration also for all-electric, new construction ADUs. Sections include a cost benefit analysis, case studies on lessons learned from retrofitted homes, and an extensive product guide.

Professional Services for ADUs

Directories to help identify companies and professionals who offer ADU services

ADU Builders, Architects, and Designers in California and nationally – Volunteer-managed list aggregating self identified companies that offer ADU services.

ADU Specialists – Accredited professionals that have completed training to help homeowners with site eligibility, development process and cost, and return on investment for ADUs.

Finance and Incentives for ADUs

Other organizations supporting ADUs

Alex Coba

Communications Associate

As a proud California native from Stockton, Alex brings a wealth of experience and a versatile skill set. He has a solid communication background with a Bachelor of Arts in Journalism and Public Relations from California State University, Chico. Alex is adept at strategic communications and media relations, with experience gathering and sharing stories from his local communities that uplift the unique spirit and values of those places. He is excited to join Build It Green, where he can apply his talents to further BIG’s mission to help communities across California thrive.