Mandatory, Prescriptive and Performance: The Three Parts of Every Title 24 Report
Mandatory measures are the floor every building must meet. On top of that floor a building follows either the prescriptive recipe, a fixed table of values by climate zone, or the performance approach, a computer comparison against a standard design. Performance can trade features but never skips the mandatory floor.
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Think of layers, not three options
People often read the three words as a menu. The Standards stack them: a new single-family building meets the mandatory measures (Sections 110.0 to 110.10 and 150.0) and then one of two routes, performance (Sections 150.1(a) and (b)) or prescriptive (Sections 150.1(a) and (c)). Multifamily and nonresidential buildings follow the same two-step shape in their own sections (Section 100.0(e)2).
Layer one: the mandatory floor
These apply whatever route you choose. Examples include a minimum U-factor of 0.40 as the weighted average for fenestration (Section 150.0(q)) and an overall wall assembly U-factor of 0.095 for 2x4 framing (Section 150.0(c)). Because they apply on both routes, they are the rules a trade-off never touches.
Layer two, route A: prescriptive
A prescriptive building meets every requirement of Table 150.1-A for its climate zone, where "NA" means not allowed and "NR" means no requirement. It is rigid by design: for example, the space-conditioning system must be a heat pump (Section 150.1(c)6). A building that misses one value must change the design or switch routes.
Layer two, route B: performance
Here the proposed design is compared with a standard design built by applying the mandatory and prescriptive requirements to your building, so a strong feature can offset a weak one. Two things the model does not do for you: it cannot erase a mandatory measure, and the manual warns that software may not automatically check the mandatory measures, so that check still has to happen.
Which layer is your project probably using?
- New home: either route is open to it, and the choice is the designer's.
- Addition or alteration: generally prescriptive, with performance as an option (Section 150.2).
- Unsure: the form number says which one (CF1R-NCB-01 is prescriptive for new buildings, while performance reports come from compliance software), and how to read a CF1R walks through it.
For the cost of choosing, see the prescriptive versus performance comparison, and for the floor itself the residential mandatory measures. Our residential reports cover both routes.
Common Title 24 Questions
- What is Title 24?
- Do I need a Title 24 report?
- How much does a Title 24 report cost?
- How long does a Title 24 report take?
- What is included in a Title 24 report?
- What plans do I need to upload?
Frequently Asked Questions
No. Mandatory measures must be met on either route, and the software may not check them for you.
It does not use the table as a checklist. The standard design is built from the prescriptive requirements, and your proposed design has to use no more energy than that budget.
Explore What Is Title 24?
- What Are the Parts of Title 24, and Which Is the Energy Code?
- Residential vs Nonresidential Title 24: Which Rules Apply?
- Does Title 24 Require a Smart Thermostat?
- Title 24 Accessibility vs the Energy Code: Which Do You Mean?
- Where to Find the Title 24 Code PDF
View all What Is Title 24? guides → · Title 24 Guide · Title 24 guide