Why Did My Title 24 Calculation Change? Seven Reasons the Result Moves

Start with what the two reports print

A performance CF1R shows the calculation date and time on every page, and a registered one carries a revision digit that rises each time it is re-registered (JA7.5.2.3 and JA7.5.6.2). Two dates with two results already narrows the search. Then read the special features list, which names what must be installed for the building to comply.

Seven causes

1. The plans moved. Section 10-109(c)1A generates the standard design automatically from the inputs describing the proposed building, so an added window or new heater changes the target too.
2. Glass passed 20 percent. In a new building the standard design matches your glass only up to 20 percent of conditioned floor area, spreads it evenly over four sides and gives it no overhangs, so extra west glass costs more than its area suggests.
3. Orientation or address. Orientation is the actual azimuth of the front of the building, and climate zone follows the address or ZIP code. Correcting either changes the weather and the budget.
4. A software update. The modeling rules are revised no more than twice a year, in January and July, and an earlier software version expires 60 or 90 days after its replacement is approved (Section 10-116(d)).
5. The existing house was treated differently. In an alteration, Table 150.2-G sets the standard design for an altered component with or without third-party verification of existing conditions, and the two columns give different answers.
6. A verified feature came or went. Performance above the minimum has to be field verified (Section 150.1(b)2B), so dropping that test removes the credit.
7. The scope changed. Components not altered are held at existing conditions, so adding one altered component adds a requirement.

What to do with the answer

If the new result relies on something the drawings do not show, the plans must match it; the architect-changes page explains. A report is tied to its edition and design (how long a report is valid), and the guide to reading a CF1R maps each block. Residential Title 24 reports include revisions until the project complies.

Common Title 24 Questions

1. What is Title 24?
2. Do I need a Title 24 report?
3. How much does a Title 24 report cost?
4. How long does a Title 24 report take?
5. What is included in a Title 24 report?
6. What plans do I need to upload?

Frequently Asked Questions

Can the same house pass one week and fail the next?

Does a new software version always change the result?

Explore Title 24 Reports

1. Remodeling a Condo: Title 24 for Unit Owners
2. A Landlord's Guide to Title 24 Upgrades
3. SB 9 Lot Splits and Title 24
4. Title 24 for House Flippers and Investors
5. The Title 24 Joint Appendices, JA1 to JA18

View all Title 24 Reports guides → · Reports and Calculations · Title 24 guide