Title 24 for an Older Home With Unknown Insulation
Unknown insulation does not block a permit. For an altered component the performance method can assume code-level values, or an ECC-Rater can verify the existing insulation before construction. Which route pays better depends on how poor the old insulation really is.
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The default: no verification
Table 150.2-G sets the standard design for an altered ceiling, wall or raised floor. Without third-party verification it is the mandatory insulation requirements of Section 150.0(a), (c) and (d). This is the route the software takes when verification is not selected, and the compliance manual adds that where installed features are unknown, default values may be used based on the year of construction. Features you do not alter are modeled the same in the proposed and standard designs, so they cost nothing.
The option: verify before construction
With verification, the standard design becomes the existing R-value, and credit is measured against what was really in the wall or attic. The compliance manual says the existing features must be verified before construction begins and before the permit application. The ECC-Rater inspects the home, and a registered verification certificate (CF3R-EXC-20-H) is a prerequisite for registering the CF1R. Verification covers altered components only: existing walls that enclose newly conditioned space count as new.
Where the prescriptive path needs an attic reading
Altering a vented attic ceiling triggers the Section 150.2(b)1J requirements. The whole list is excepted where the dwelling already has at least R-38 at the ceiling. It is also excepted where the alteration would directly disturb asbestos, or where knob and tube wiring sits in the vented attic. To claim the R-38 exception, someone has to establish the depth. Ducts built, insulated or sealed with asbestos are excepted from the duct sealing rule.
What to do on site
- Record what you can see at an access hatch or open stud bay, and whether insulation was added later.
- Ask the department what evidence it accepts for an existing R-value.
- Decide on verification before demolition, because the rater must see the original condition.
The numbers are on insulation requirements, and what an ECC-Rater does describes who verifies. Single glazing raises the same choice, covered in existing single-pane windows. Missing drawings are covered in no existing plans. Our residential Title 24 reports use the verified route when you choose it.
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. Without verification the model uses the Table 150.2-G assumptions for altered components, and no inspection of the existing condition is needed. Ask the department what evidence it wants for any exception you claim.
No. It is optional. Without it the performance model uses the table values for altered components.
Explore Insulation
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- Attic Insulation Certificate: What the Contractor Must Give You
View all Insulation guides → · Windows and Building Envelope · Title 24 guide