Title 24 and HVAC Replacements in California: What Your Contractor Is Required to Tell You

Replacing your HVAC system in California isn’t just about picking a new AC or furnace. It is a regulated process tied to energy efficiency, safety, and performance standards under Title 24 of the California Code of Regulations. If a contractor skips steps or fails to explain the requirements, that is a red flag.

This guide explains what your contractor should cover before installation, helping you avoid costly mistakes.

Why Title 24 Matters for HVAC Replacement

Title 24 sets minimum efficiency and installation standards for HVAC systems in California homes. It’s enforced through permits, inspections, and third-party testing.

In practical terms, this means your contractor is legally required to:

• Size the system properly using load calculations.
• Evaluate and often modify ductwork.
• Meet minimum efficiency ratings.
• Pull permits and schedule inspections.
• Complete HERS (Home Energy Rating System) testing when required.

The California Energy Commission replaced the HERS program with the Energy Code Compliance (ECC) program, effective January 1, 2026. It is designed to reduce energy waste and ensure systems perform as intended in real homes.

If your contractor overlooks these key requirements, they are not in compliance with state law.

What a Legitimate HVAC Contractor Explains Before Installation

1. Load Calculations (Not Guesswork)

A proper HVAC replacement starts with a Manual J load calculation. It determines the exact heating and cooling needs of your home. Factors include:

• Square footage
• Insulation levels
• Window type and orientation
• Air leakage

Oversized systems are a common problem. They short-cycle, waste energy, and fail to control humidity.

According to ASHRAE guidelines, accurate load calculations are essential for system efficiency and comfort.

A trustworthy contractor will explain why your new system may differ in size from your old one.

2. Ductwork Evaluation and Sealing

Ductwork isn’t optional in a replacement. Title 24 often requires duct sealing and testing. This is especially true if:

• The system is over a certain capacity.
• Ducts are located in unconditioned spaces (attics, crawlspaces)

Leaky ducts can waste up to 30% of airflow.

A professional will check:

• Air leakage
• Duct sizing
• Insulation levels

If needed, they will recommend duct repair or full ductwork replacement. It is not just about swapping the unit.

When comparing options, pay attention to the estimated details. A low bid often skips duct upgrades entirely.

3. Permits and Code Compliance

Every HVAC replacement in California requires a permit for code compliance.

A legitimate contractor will:

• Pull the permit before work begins.
• Schedule city or county inspections
• Ensure all work meets Title 24 requirements.

Skipping permits may save money upfront, but creates major risks:

• Failed home inspections during resale
• Insurance issues
• Safety hazards

TheCalifornia Contractors State License Board notes that unpermitted work is a violation of Business and Professions (B&P) Code sections 7110 and 7090.

4. HERS, Now ECC Testing and Acceptance Documentation

Many HVAC replacements require verification through HERS, now ECC testing.

This includes:

• Duct leakage testing.
• Airflow verification.
• Refrigerant charge verification.

You should receive documentation proving the system passed these tests.

A contractor who says “you don’t need that” without explanation is either misinformed or cutting corners.

5. Equipment Efficiency and AHRI Matching

Your system must meet minimum efficiency standards under Title 24.

This typically includes:

• SEER2 (cooling efficiency) requirements.
• AFUE ratings for furnaces.
• Proper matching of indoor and outdoor components.

According to the California Energy Commission, the system must be AHRI-certified as a matched combination to comply with Title 24 standards. (Source: CEC). Mixing components incorrectly can void warranties and fail inspections.

6. Airflow, Thermostat, and Controls

Airflow is one of the most overlooked parts of HVAC replacement.

A qualified contractor will explain:

• Required airflow (CFM per ton).
• Static pressure limits.
• Filter sizing.

They should also discuss thermostat compatibility, especially when upgrading to a smart thermostat.

Improper airflow leads to:

• Reduced efficiency.
• Uneven temperatures.
• Premature equipment failure.

Real Example: What a Code-Compliant Replacement Looks Like

Kaleend Dharia, a homeowner, wanted a system replacement but needed clarity and flexibility throughout the process.

Instead of pushing a quick install, our team walked him through options and handled a full system upgrade that included relocating the unit to the attic, replacing ductwork, and installing a new thermostat. As he put it, “He worked with me, answered all my questions. Didn’t try to push or sell me and was fully committed to making sure I was a lifelong customer.” Read his full Google review here.

During the project, adjustments were made according to his preferences. The team addressed these modifications professionally while maintaining code compliance.

The result was a properly installed system that met code requirements and was ready for inspection. Just as important, Kaleend felt confident in the process and outcome. This combination of technical accuracy and clear communication separates a compliant installation from a risky one.

Common Red Flags to Watch For

Homeowners often get burned when contractors skip required steps. Watch for:

• No mention of permits.
• “Same size as your old unit” without calculations.
• No duct inspection.
• Prices that seem too low.
• No discussion of testing or inspections.

These shortcuts usually lead to higher long-term costs.

What You Should Expect Before Signing a Contract

Before you agree to an HVAC replacement, your contractor should clearly explain:

• System sizing and options.
• Title 24 code compliance.
• Ductwork condition and recommendations.
• Total cost, including permits and testing.
• Timeline and inspection process.
• Warranty details.

If any details are unclear, ask questions. Reputable contractors welcome inquiries.

Get a Code-Compliant HVAC Replacement Estimate

Thomson AC has 20+ years of experience, providing cooling and heating solutions as a complete, code-compliant project, not just a quick equipment swap. That means you get a system that performs correctly, passes inspection, and holds up over time.

Here’s what’s included in a proper replacement estimate with our team:

• Manual J load calculation to size your system accurately.
• Full duct evaluation with sealing or replacement if needed.
• AHRI-matched equipment selection for efficiency and warranty protection.
• Permit handling so your installation is legal and documented.
• HERS, ECC testing coordination when required under Title 24.

Just as important, we take the time to explain everything before the work begins. No vague answers. No pressure. No skipped steps.

If you want to avoid failed inspections, comfort issues, or costly rework later, schedule your code-compliant HVAC replacement estimate with Thomson AC today.

FAQs

Do all HVAC replacements in California require permits?

Yes, permits are required for system replacements to ensure compliance with Title 24 and local building codes.

What is HERS testing, and do I need it?

HERS testing verifies system performance, such as airflow and duct leakage; many replacements require it, depending on the scope of work.

Can I replace my HVAC system without changing the ductwork?

Sometimes, but only after proper testing. If ducts leak or are undersized, replacement or sealing is often required.

How do I know if my system is properly sized?

A contractor should do a Manual J load calculation. Without this, the sizing is likely a guess.

Why are some HVAC replacement quotes much cheaper?

Lower quotes often exclude permits, ductwork, or testing, which can lead to failed inspections and poor system performance.