Understanding CA's Residential Energy Code: An easy-to-read Summary


As of July 1st 2014, California’s newest version of the Energy Efficiency Standards Code will be in effect.  Since it’s revised every 5 years or so and aims to reduce energy consumption by ±25% each time, let’s just call this what it is:  “a big deal”.

All projects submitted to the Building Department after June 30th 2014 must comply with the updated version of this Code, including:  New Construction, Additions, Alterations, and Repairs.


Over the years, California has implemented and regularly updated these standards in order to reduce buildings' consumption of electricity and natural gas, for the benefit of the Homeowner, the Economy, and the Environment.  According to California's Energy Commission, Californians have saved “more than $74 billion in reduced electricity bills since 1977" as a result of these standards (calculated by multiplying annual cumulative savings by the average electricity rate that year).

Focus of this Article:

The focus of this particular article is to better understand the "low-rise" residential standards, although it should be noted that commercial buildings certainly play a big part of the energy demand reduction equation.  The term "low-rise" refers to:  all single-family dwellings, all duplexes, and multi-family buildings with three or fewer habitable stories.

Code Title Terminology (feel free to skip this paragraph):

In effect as of July 1st 2014 are the “2013 Title 24 California Building Energy Efficiency Standards” (the most recent update since the 2008 version that was adopted in January of 2009).  The complete "2013 Residential Compliance Manual" is more than 550 pages long, not including the Forms, and intended as a supplementary guide to the overarching and larger "2013 Title 24 California Building Energy Efficiency Standards” document.

Building Components & Assemblies:

Here’s a general overview of some of the characteristics, components, and assemblies that affect Residential Building Energy Demand, and therefore are inherently regulated in some way by this Code:

> GENERAL CHARACTERISTICS such as:  Climate; Building Orientation; Consideration for Existing Conditions of Additions, Alterations, and Repairs (through Third-Party Verification)

> BUILDING ENVELOPE such as:  Construction Assemblies; Materials; Insulation; Air Leakage & Infiltration; Thermal Mass; Passive Solar Design; Overhangs & Shading Devices; Fenestration & Glazing (size, properties, location); Glazing Properties; Roofing Material; Solar Reflectance; Emissivity; Thermal Emittance; Radiant Barrier; Air Barrier; Attic Space & Conditioning; Floor Construction; Crawl Space; Basements, Garages, & Storage Space

> MECHANICAL SYSTEM such as:  Heating & Cooling Equipment; Distribution (Ducts, Plenums, Fans);  Duct Leakage, Design Diagnostics, & 3rd Party Verification & Testing; Indoor Air Quality; Ventilation (Natural vs. Mechanical); Conditioned Floor Area; Ceiling Heights; User Controls (Thermostats & Zoning)

> DOMESTIC HOT WATER such as:  Water Heating System; Distribution (Piping); Heat Element Source; Insulation; Solar Water Heating; Swimming Pool & Spa Heating

> LIGHTING & ELECTRICAL such as:  Switching Devices & Controls (Dimmers, Vacancy Sensors, etc.); Efficacy of Fixtures; Type of Luminaire (ie, LED); Lighting by Room (Kitchen, Bathroom, Garage, Laundry, Utility); Outdoor Lighting; Solar Power

How to Comply:

If this seems complicated so far, not to worry:  Your Architect will coordinate the entire process and will consult with an energy consultant as necessary to ensure your project is designed in compliance, which will be represented on a variety of forms within the Construction Drawing package that is submitted to the local regulatory agency for plan check and permitting.  Inspections and Certifications during construction will be coordinated by your Contractor and checked off by the building inspector.

MANDATORY MEASURES:  There are two different compliance “approaches” described below, but in either case, the project must at a minimum comply with the Mandatory Measures.  This includes things like lighting control, lighting efficiency, minimum insulation levels, infiltration control, equipment efficiency, third-party verification for mechanical duct sealing and leaking, airflow and fan efficacy, and certain ventilation system requirements.

Beyond the list of (minimum) Mandatory Measures, one of the two following “approaches” is also required for compliance.

THE PRESCRIPTIVE APPROACH:  (AKA “Package A”) This approach offers a Package of pre-defined requirements for building components based on the project's location (by Climate Zones).  Generally speaking, it’s an easy-to-use checklist, but because each individual component or item on the list is required to comply with a certain minimum efficiency, there is very little design flexibility.  Consider, as an example, a non-negotiable requirement such as this:  the total allowed amount of west-facing fenestration (windows) is allowed to be no more than five percent of the project's overall conditioned floor area.  What if your property boasts a sweet west-facing view of the Pacific Ocean and you wanted a giant window-wall facing west?  [Answer:  use the Performance Approach instead!]

THE PERFORMANCE APPROACH:  This approach is admittedly more complicated, and requires certain computer software to actually model building performance to calculate and verify that the proposed design’s energy use will meet its allowed energy budget.  The budget is derived from a similar model of the exact same building if it were to theoretically comply via the prescriptive approach’s list of requirements.  The performance approach, however, factors in the type of energy used (electricity, gas, etc.) and the time at which it is used.  For example, energy at times of peak demand is valued higher than energy at times of greater supply.  Because trade-offs are available, there is much more design flexibility with this approach.  Using the same example as above, with the performance approach, you can have your giant west-facing window wall if we save energy another way, such as using super high-performance glass, or providing a large shade overhang, etc. 

Although the Performance approach may sound more complex than the Prescriptive approach, the cost for the computer modeling (as low as just a few hundred dollars) is often dwarfed by potential savings stemming from being able to make trade-offs in seeking the more cost-effective design solution.


This Energy Code update, although seemingly complicated and cumbersome, is most certainly a necessary evil.  It is California’s goal to one day require all new buildings, or renovated portions thereof, to use no more energy than they create, and this Code with its periodic updates is the mechanism through which this will be possible.

Your Architect will gladly guide and facilitate your project’s compliance, as this Code change is still only one very small piece of the much larger puzzle that is building or renovating a house.  If you have any questions or need help with your project, contact us at TrèSpace Studio anytime.


Source: http://www.energy.ca.gov/title24/