9.2 HERS Verification & Duct Testing Requirements

California C-20 HVAC Contractor License CSLB

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1 Chapter 1: Introduction & CA C-20 License Overview

1.1 About the California C-20 HVAC Contractor License & CSLB Exam Path 1.2 License Eligibility, Experience Requirements & Application Process 1.3 Exam Format, Scoring, Retakes & Bond/Insurance Activation

2 Chapter 2: CSLB Licensing Law & Business Organization

2.1 CSLB Structure, License Classifications & the C-20 Scope of Work 2.2 Business Entity Types, Qualifying Individuals & RME/RMO Rules 2.3 Advertising Rules, License Number Disclosure & Subcontracting 2.4 License Renewal, Inactive Status, Violations & Disciplinary Actions

3 Chapter 3: Business Finances & Taxes

3.1 Business Accounting Principles & Financial Statements 3.2 Cash Flow Management & Business Planning 3.3 Federal & California Tax Obligations for Contractors 3.4 Financial Reporting & Recordkeeping Requirements

4 Chapter 4: Contracts, Bidding & Estimating

4.1 Home Improvement Contract (HIC) Requirements & Mandatory Disclosures 4.2 Service & Repair Contracts, Cancellation Rights & Notice Requirements 4.3 Commercial Contracts, Bidding Procedures & Cost Estimating 4.4 Change Orders, Progress Payments & Contract Administration 4.5 Contract Breach, Warranties & Dispute Resolution

5 Chapter 5: Insurance, Bonds & Mechanics Liens

5.1 Contractor's License Bond & Qualifying Individual Bond Requirements 5.2 Workers' Compensation Insurance & Exemption Rules 5.3 Commercial General Liability & Property Insurance 5.4 Mechanics Liens, Preliminary Notices & Stop Payment Notices

6 Chapter 6: Employment Law, Payroll & Public Works

6.1 Hiring, Employee vs. Independent Contractor Classification 6.2 Wage & Hour Law, Overtime & Payroll Requirements 6.3 Employee Supervision, Training & Certified Payroll Recordkeeping 6.4 Termination, Final Pay & Employment Recordkeeping 6.5 Public Works: Prevailing Wage, Apprenticeship & DIR Compliance

7 Chapter 7: Cal/OSHA & Legal Safety Compliance

7.1 Cal/OSHA Injury & Illness Prevention Program (IIPP) & Recordkeeping 7.2 Jobsite Hazard Communication, PPE & Training Requirements 7.3 Asbestos, Lead & Hazardous Materials Handling Rules 7.4 Accident Reporting, Emergency Action Plans & Cal/OSHA Enforcement

8 Chapter 8: HVAC Planning, Load Calculations & Estimating

8.1 Jobsite Evaluation, Blueprint Reading & System Selection 8.2 Manual J Heat Load & Heat Gain Calculations 8.3 Psychrometrics & Air Properties for HVAC Design 8.4 Duct Design & Sizing (Manual D) & Airflow Balancing 8.5 Material & Labor Estimating for HVAC Projects

9 Chapter 9: California Title 24 Energy Code & Mechanical Code Compliance

9.1 Title 24 Part 6 Energy Code Requirements for HVAC Systems 9.2 HERS Verification & Duct Testing Requirements 9.3 California Mechanical Code (CMC) Key Provisions for C-20 Work 9.4 Permits, Inspections & Code Compliance Documentation

10 Chapter 10: Equipment Installation, Ductwork & System Startup

10.1 Equipment Setting, Mounting & Clearances 10.2 Ductwork Fabrication, Sealing & Insulation 10.3 Refrigerant Piping, Brazing & Soldering Techniques 10.4 Electrical & Control Wiring for HVAC Systems 10.5 System Charging, Combustion Venting & Startup/Commissioning

11 Chapter 11: Refrigeration Cycle, Heat Pumps & Solar-Thermal

11.1 Refrigeration Cycle Fundamentals & Components 11.2 Heat Pump Systems & Water Heating Heat Pumps 11.3 Solar-Thermal HVAC Integration

12 Chapter 12: Troubleshooting, Repair & Maintenance

12.1 Electrical Component Diagnostics & Thermostat/Control Troubleshooting 12.2 Mechanical Failure Analysis & Compressor/Motor Diagnostics 12.3 Refrigeration Cycle Diagnostics & Combustion/CO Troubleshooting 12.4 Preventive Maintenance Programs & Service Procedures

13 Chapter 13: Trade Safety & EPA Refrigerant Regulations

13.1 Cal/OSHA Jobsite Safety, PPE & Ladder/Fall Protection 13.2 EPA Section 608 Refrigerant Recovery, Recycling & Handling 13.3 Combustion Venting, Carbon Monoxide & Confined Space Safety 13.4 Hazardous Materials on HVAC Jobsites (Asbestos, Lead, Refrigerant Oil)

9.2 HERS Verification & Duct Testing Requirements

Key Takeaways Explain This Topic AI

A HERS (Home Energy Rating System) rater is an independent, CEC-approved third party -- not affiliated with the installing contractor -- who performs required diagnostic field tests and registers the results into a state-recognized system.

HERS verification is triggered by new construction, by duct alterations exceeding 40 linear feet of replaced ductwork, and by most HVAC equipment change-outs completed under the applicable alteration (ALT) compliance forms.

Duct systems that qualify as 'new' (75% or more new duct material, with up to 25% reused) must meet the tighter 5% new-construction leakage threshold; alterations that retain most of the existing ductwork are held to a looser 15% total leakage threshold.

Duct leakage is measured in CFM25 -- cubic feet per minute of leakage recorded while a calibrated duct blaster fan pressurizes the system to a standardized 25 pascals.

The 2025 cycle expanded mandatory HERS refrigerant-charge verification for heat pumps to every California climate zone and added mandatory airflow and fan efficiency testing for new HVAC systems.

Last updated: July 2026

What a HERS Rater Does

HERS stands for Home Energy Rating System , a diagnostic testing and rating framework that originated nationally through the Residential Energy Services Network (RESNET) and was adopted into California's Title 24 enforcement structure as the mechanism for confirming, in the field, that certain mandatory and prescriptive energy measures were actually built the way the paperwork claims. A HERS rater is an individual who has completed CEC-approved (and typically RESNET-accredited) training and certification to perform these tests. Note that in recent CEC communications the terminology has begun shifting toward " Energy Code Compliance (ECC) " branding for providers and raters; the underlying CF-form numbering and testing requirements discussed in this section continue regardless of which label a given jurisdiction or provider currently uses, so C-20 candidates should recognize both terms.

The defining feature of a HERS/ECC rater is independence : the rater must be a disinterested third party with no financial relationship to the installing contractor, which preserves the integrity of the verification. A rater is not part of the contractor's crew, does not report to the contractor, and is not paid contingent on the installation passing. In practice, the rater is typically engaged (and paid) by the contractor or builder as a required part of the project, but their certification and test results are filed independently into a state-recognized registry maintained by an approved HERS/ECC Provider organization.

On a jobsite, a HERS rater's core responsibilities include:

Duct leakage testing -- pressurizing the duct system with a calibrated fan and measuring the CFM25 leakage rate against the applicable threshold.

Refrigerant charge verification -- confirming the system was charged correctly (commonly via the superheat or subcooling method referenced against manufacturer specifications), now mandatory statewide for heat pumps under the 2025 cycle.

Airflow and fan watt draw testing -- confirming the system delivers its rated airflow and that fan energy consumption meets the applicable limit, mandatory on new HVAC systems under the 2025 cycle.

Registering results and issuing the CF3R -- the Certificate of Field Verification and Diagnostic Testing (fully covered in Section 9.4), which the local building department relies on before finaling the permit.

When HERS Verification Is Triggered

HERS/ECC verification is not limited to brand-new homes. C-20 contractors encounter it across several common scenarios:

New construction -- any system subject to the mandatory or prescriptive measures of the applicable Energy Code cycle requires field verification as a matter of course.

Duct replacement or extension -- testing is generally triggered once more than 40 linear feet of existing ductwork is replaced . Whether the tighter new-construction threshold or a looser alteration threshold applies depends on how much of the system is new material (see the table below).

Equipment change-outs -- most full replacements of a furnace, air conditioner, or heat pump trigger HERS verification of refrigerant charge and, where ductwork is involved, duct leakage, filed under the applicable alteration compliance forms (commonly labeled with an "-ALT" suffix, such as CF1R-ALT).

Substantial duct sealing work -- projects whose scope is specifically to seal and improve an existing duct system are verified to confirm the improvement was actually achieved, not merely claimed.

Duct Leakage Thresholds

Duct leakage testing measures air escaping the duct system in CFM25 -- cubic feet per minute of leakage recorded while a calibrated duct blaster fan pressurizes the system to a standardized 25 pascals test pressure. This standardized pressure allows results from different jobs, raters, and equipment to be compared consistently under the RESNET testing protocol that California's field verification procedures reference.

The allowable leakage percentage is not a single flat number -- it scales with how much of the duct system is new versus existing:

Scenario Maximum Total Leakage

All-new duct system (75% or more new material; up to 25% may be reused) -- treated the same as new construction 5%

Altered system retaining most existing ductwork (typical equipment change-out without a substantial duct replacement) 15%

• Duct extensions exceeding 25 linear feet 10% total, or 7% to the outside
• Ducts routed through an unconditioned garage 6%

Because duct leakage percentages have tightened across recent code cycles (the prior 2019/2022 cycle used a 6% new-construction threshold before the 2025 cycle reduced it to 5%), a contractor should always confirm the exact figure against the code cycle governing the permit in hand rather than relying on a number learned on a previous job -- the applicable cycle depends on the permit application date discussed in Section 9.1.

What Happens When a System Fails Testing

If a HERS/ECC rater's test results exceed the applicable threshold, or refrigerant charge is out of range, the system does not pass. The contractor must correct the deficiency -- commonly by sealing additional duct joints with mastic or by adjusting refrigerant charge to the manufacturer's specification -- and the rater must retest before a passing CF3R can be filed. Because a retest typically means scheduling a second rater visit at additional cost and delay, experienced C-20 contractors build a margin of safety into their own duct sealing and charging practices rather than aiming to just barely clear the threshold, treating the HERS test as a checkpoint to pass comfortably rather than a target to meet exactly.