HERS (Home Energy Rating System) testing is third-party field verification under Title 24, performed by certified raters (not the builder/contractor) to confirm installed features match the report. It uses diagnostic tools for:
- Duct leakage (≤5-15% depending on location).
- Refrigerant charge (for AC efficiency).
- Airflow (≥350 CFM/ton).
- Insulation depth/visual (Quality Installation—QI).
- Blower door (air infiltration).
Mandatory for new HVAC, ducts in unconditioned spaces, and high-performance credits. Raters document on CF3R forms; failure requires fixes before final inspection.