# §110.8: Mandatory installation requirements
What it requires
§110.8 is the "quality of installation" section — it sets minimum standards for how insulation, fenestration, HVAC equipment, ducts, and air barriers must physically be installed. A spec sheet that lists R-21 walls doesn't satisfy §110.8 if the batts are stuffed in around wiring with gaps and compressions; the installed assembly has to actually deliver the rated performance.
The headline rules:
- Insulation installation quality — Grade I, II, or III per RESNET, with Grade I being the field-verifiable baseline. Compression, gaps, and missed studs drop the assembly into Grade II or below.
- Fenestration installation — flashing, weather-stripping, and rough-opening sealing per manufacturer specs.
- Duct sealing — mastic at every joint, no cloth-backed duct tape.
- HVAC commissioning — refrigerant charge, airflow per ton, and outdoor / indoor coil match per Reference Joint Appendix JA1.
- Air barrier continuity — drywall, sheathing, and joints sealed so the air barrier is contiguous around the conditioned envelope.
§110.8 hands the field verification to the ECC Rater (CHEERS field- verification credential) for the items that the AHJ inspector can't practically check — refrigerant charge, airflow, duct leakage, blower-door test.
When it applies
- Every California residential project — new construction, additions, and alterations.
- Field-verified items are listed on the CF1R as required CF3R measures.
How we use it
The Title 24 compliance verification report lists every §110.8 field- verified measure that applies to your project — typically envelope blower- door test, duct leakage test, refrigerant charge, airflow, and HPWH verification when applicable. We coordinate the field verification through our ECC Rater credential as part of project close-out.
The designer-CF1R checklist surfaces the §110.8 items the designer must sign for before the report goes out (insulation grade, fenestration installation per spec, etc.).
Common gotchas
- Insulation rated "R-21" that's installed at Grade II — the de-rated effective R-value drops the assembly below the prescriptive target and the project fails compliance even though the spec sheet was fine.
- HVAC equipment installed to manufacturer specs but with no commissioning report — §110.8 requires the JA1 commissioning data on file before final.
- Air-barrier continuity broken at the rim joist between floors — the wall and floor each test fine, but the seam between them isn't sealed and the §110.7 blower-door test fails.