Title 24 Compliance
There are two methods for achieving Title 24 compliance in California. The most flexible method of Title 24 compliance is the performance method.
- Prescriptive Method: The simplest approach to Title 24 compliance where each individual component of the proposed building must meet a prescribed minimum energy requirement. The prescriptive approach is the least flexible yet simplest compliance path. It is simple because an applicant need only show that a building meets each minimum or maximum level prescribed in the set of requirements contained in a package. Unlike the performance method the prescriptive method imposes an upper limit on the number of windows allowed. The prescriptive method is not recommended for new homes or larger additions, and can result in higher construction costs.
- Performance Method: The use of Energy Commission-approved computer methods provides the most flexibility and accuracy when seeking Title 24 compliance. Detailed accounting of energy trade-offs between measures is possible with this compliance approach. While this approach requires the most effort, it also provides the greatest flexibility. The computer program automatically calculates the energy budget for space conditioning. The budget is determined from the standard design, a version of the building, which is upgraded or downgraded to achieve minimum compliance with the prescriptive package conservation features.
With the performance method the energy budget for space conditioning is expressed in thousands of Btu (kBtu) per square foot per year. The program also calculates the budget for water heating energy use in kBtu per dwelling unit. The water-heating budget is translated into a kBtu per square foot per year value and added to the space-conditioning budget to yield the combined energy budget. To comply with the Standards, the predicted combined "Energy Use" of the Proposed Design cannot exceed the combined "Energy Budget" of the Standard Design.
Mandatory Measures and Title 24 Compliance
With either of these Title 24 compliance paths, there are mandatory measures that still must be installed. The mandatory measures require minimum ceiling, wall, and raised floor insulation; minimum HVAC (heating, ventilating and air conditioning) and water heating equipment efficiencies, and other requirements. The mandatory measures are required features with either the prescriptive or performance standards. Where superseded by a more stringent requirement to achieve compliance with the energy budget or prescriptive package, the more stringent feature becomes mandatory.
(Excerpted from the CEC Title 24 Residential Compliance Manual)