California’s Title 24 energy code is designed to reduce wasteful and unnecessary energy consumption in both newly constructed and existing buildings. The California Energy Commission updates the building energy efficiency standards (Title 24, Parts 6 and 11) every three years by working with stakeholders in a public and transparent process.
Created by the California Building Standards Commission in 1978 as a response to legislation mandating the reduction of California's energy consumption, the California Building Standards Code has resulted in notable advances in the state's energy policy.
Three general components make up the structure of California's energy code - mandatory requirements, performance standards, and prescriptive standards.
Mandatory Requirements: These measures cover subjects from infiltration control and lighting to minimum insulation levels and equipment efficiency. Occasionally these minimum levels are superseded by stricter prescriptive or performance requirements. If mandatory measures specify R-22 ceiling insulation and prescriptive compliance is being used, then R-30 or R-38 insulation (depending on climate zone) must be installed.
Prescriptive Method: This approach utilizes a set of predefined performance levels. While using prescriptive standards is the simplest route it is also the least flexible. With this method each building component must meet or exceed the minimum efficiency levels specified in California's energy code.
Performance Method: The performance method, while more complicated, offers considerably more design flexibility. Also known as the computer compliance method, energy compliance is met here using an approved software program to model proposed construction and compare it to a calculated energy budget. This method is far more popular because of its flexibility and ability to provide the most cost-effective compliance solution. Performance compliance is based on the following factors:
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Glazing efficiency and orientation
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Shading from overhangs
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Space conditioning system efficiency
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Water heating system efficiency
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Insulation values
Excerpted from the CEC Title 24 energy compliance manual
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California Climate Zones
The energy commission split California into 16 zones and has established standard climate data for each. These zones allow for standardized calculations and provide a basis for presenting prescriptive requirements. To determine which climate zone your project is in the CEC developed the EZ Building Climate Zone Search Tool.
