Title 24 Compliance for HVAC Systems in San Francisco

Title 24, Part 6 of the California Code of Regulations establishes the mandatory energy efficiency standards that govern HVAC equipment selection, duct design, mechanical ventilation, and commissioning in California buildings. In San Francisco, these state-level requirements intersect with local reach codes, the city's all-electric construction mandates, and the Department of Building Inspection's permit review process to create a compliance environment more demanding than the state baseline alone. This page maps the regulatory structure, mechanics, and classification boundaries that define Title 24 HVAC compliance specifically within San Francisco's jurisdiction.

• Definition and scope
• Core mechanics or structure
• Causal relationships or drivers
• Classification boundaries
• Tradeoffs and tensions
• Common misconceptions
• Checklist or steps (non-advisory)
• Reference table or matrix
• References

Definition and scope

Title 24, Part 6 of the California Code of Regulations is California's formally designated energy efficiency code, administered by the California Energy Commission (CEC). It is updated on a triennial cycle; the 2022 California Energy Code took effect on January 1, 2023. For HVAC systems, Part 6 is the primary governing document, establishing prescriptive and performance-based requirements for heating, cooling, ventilation, and duct systems across all occupancy types.

Part 11 of Title 24 — the CALGreen Code, administered by the California Building Standards Commission (CBSC) — supplements the energy code with green building mandates including refrigerant management, commissioning thresholds for mechanical systems, and indoor air quality prerequisites. Both parts apply concurrently to HVAC work in San Francisco.

Geographic and jurisdictional scope of this page: This reference covers HVAC-related Title 24 compliance requirements as they apply within the City and County of San Francisco. San Francisco's Department of Building Inspection (DBI) enforces Title 24 through its permit review and inspection process. Adjacent jurisdictions — Oakland, Daly City, San Mateo County — operate under the same state code but administer enforcement independently and are not covered here. California state agencies, including the CEC and CBSC, set baseline standards; San Francisco's local amendments and reach codes apply on top of the state floor and are enforced by DBI and the San Francisco Environment Department. Federal programs, military installations, and tribal lands within or near San Francisco are outside this scope.

The HVAC provisions of Title 24, Part 6 apply to:

• New residential construction (single-family and multifamily)
• New nonresidential construction (commercial, retail, mixed-use)
• Alterations and replacements that meet defined thresholds (e.g., replacement of the entire HVAC system or duct system serving conditioned space)
• Additions to conditioned floor area exceeding the thresholds set in Section 100.0 of the California Energy Code

Equipment-only swap replacements of identical capacity in existing systems may qualify for a limited-scope exemption, but duct modifications or changes in fuel source typically trigger full compliance review. The San Francisco permit and inspection framework governs when a permit is required regardless of Title 24 threshold determinations.

Core mechanics or structure

Title 24 Part 6 provides two compliance pathways for HVAC systems: prescriptive and performance.

Prescriptive compliance requires that each system component meets explicit minimum standards defined in the applicable tables and sections of the code. For HVAC, the primary prescriptive requirements include:

• Minimum equipment efficiency ratings: Heating seasonal performance factor (HSPF2) for heat pumps, seasonal energy efficiency ratio (SEER2) for cooling equipment, and annual fuel utilization efficiency (AFUE) for gas-fired furnaces — all governed by Section 150.1 for residential and Section 140.4 for nonresidential occupancies of the 2022 California Energy Code.
• Duct sealing and insulation: Ducts in unconditioned spaces must meet specific leakage rates verified by a HERS (Home Energy Rating System) rater. The 2022 code requires total duct leakage of no more than 15% of system airflow for altered duct systems and 6% for new duct systems — verified through a pressure test conducted by a HERS rater certified by the California Energy Commission.
• Mechanical ventilation: Systems must comply with ASHRAE 62.2 (residential) or ASHRAE 62.1-2022 (nonresidential) ventilation rates, with California amendments. Demand-controlled ventilation (DCV) is required in certain occupancies under Section 120.1.
• Thermostatic controls and setback capability: Section 110.2 requires programmable or smart thermostat capability in all new and replacement HVAC installations.

Performance compliance uses energy modeling software — principally CEC-approved software such as EnergyPlus or CBECC-Res — to demonstrate that the proposed building design will consume no more energy than the standard design baseline. Performance compliance provides flexibility in trading off component efficiency against other measures (envelope insulation, window performance, lighting) and is commonly used in San Francisco's older building stock where prescriptive duct requirements are impractical. The relationship between San Francisco's climate and HVAC sizing decisions affects the baseline inputs used in performance modeling.

HERS verification is a mandatory third element: certain measures — duct leakage testing, refrigerant charge verification, fan airflow measurement — require field verification by a certified HERS rater before the Certificate of Compliance is issued and the permit can close.

Causal relationships or drivers

The stringency of Title 24 HVAC provisions in California — and particularly in San Francisco — is driven by four identified policy and technical factors:

1. California's climate zone classification: San Francisco falls within CEC Climate Zone 3, characterized by mild temperatures, marine influence, high summer fog frequency, and low cooling degree days. Climate zone assignment directly determines the prescriptive minimum equipment efficiency tiers and the heating/cooling load assumptions embedded in the performance baseline. Zone 3 thresholds differ materially from inland zones. The fog and humidity profile of San Francisco is a structural factor in these zone definitions.

2. Senate Bill 100 and the 2045 clean energy mandate: California's SB 100 (2018) requires that retail electricity be 100% zero-carbon by 2045. The CEC has embedded this trajectory into successive Title 24 cycles by raising electric heat pump efficiency thresholds and reducing the assumed carbon intensity credit given to gas-fired equipment in performance compliance calculations.

3. San Francisco's all-electric reach code: Adopted under authority granted by California's Building Standards Law (Health and Safety Code Section 17958.7), San Francisco's Ordinance 201-20 and subsequent amendments prohibit natural gas infrastructure in most new construction. This reach code does not replace Title 24 — it operates alongside it, narrowing the fuel-choice options available within the prescriptive pathway. All-electric HVAC conversions in San Francisco are directly shaped by this overlay.

4. Bay Area Air Quality Management District (BAAQMD) rules: The BAAQMD regulates combustion emissions from HVAC equipment operating within the Bay Area Air Basin. Regulation 9, Rule 4 (NOx emissions from space heating equipment) imposes appliance-level emissions limits that constrain the permissible gas-fired heating equipment options regardless of Title 24 efficiency compliance.

Classification boundaries

Title 24 HVAC compliance requirements branch along two primary classification axes: occupancy type and system type.

By occupancy:
- Low-rise residential (≤3 stories): Governed by Section 150.0–150.2 of the California Energy Code. HERS verification is mandatory for most mechanical measures.
- High-rise residential (≥4 stories) and nonresidential: Governed by Sections 140.4 and 120.x. Nonresidential systems require a mechanical engineer of record and separate commissioning documentation.
- Mixed-use: Each occupancy portion is evaluated under its applicable residential or nonresidential section. San Francisco's dense mixed-use stock frequently requires split compliance documentation.

By system type:
- Split systems and packaged units: Subject to SEER2/HSPF2 minimums and refrigerant charge verification.
- Variable refrigerant flow (VRF) systems: Evaluated under the nonresidential pathway; minimum efficiency expressed as energy efficiency ratio (EER) and coefficient of performance (COP).
- Hydronic systems: Boiler efficiency (AFUE or thermal efficiency) requirements apply; pipe insulation is required per Section 120.3. Hydronic heating systems in San Francisco carry specific compliance considerations for zoning and control equipment.
- Ductless mini-split systems: Covered under the same SEER2/HSPF2 thresholds as ducted equipment; duct leakage testing is not applicable but refrigerant charge verification remains required. Ductless mini-split systems in San Francisco represent a growing share of new residential installs.
- Ventilation-only systems (ERVs, HRVs, exhaust fans): Governed by Section 150.0(o) for residential. Minimum sensible recovery effectiveness thresholds apply to energy recovery ventilators. Nonresidential ventilation-only systems are evaluated against ASHRAE 62.1-2022 requirements as adopted with California amendments under Section 120.1.

Tradeoffs and tensions

Prescriptive vs. performance pathway: The prescriptive path offers administrative simplicity but is inflexible with San Francisco's aging housing stock. Victorian and Edwardian buildings typically lack accessible attic or wall cavities for duct runs meeting the prescriptive sealing requirements; performance modeling allows designers to offset with envelope measures. The tradeoff is that performance modeling requires a licensed energy consultant and extends the permit preparation timeline, adding cost before construction begins. The HVAC considerations for San Francisco Victorian homes context illustrates where this friction is most acute.

Equipment efficiency vs. installed performance: High-SEER2 equipment certified at the nameplate level can underperform compliance assumptions when installed in systems with oversized ducts, poor refrigerant charge, or improper airflow — all of which occur in retrofit conditions. Title 24's HERS verification requirement exists precisely to close this gap, but HERS scheduling delays are a real administrative friction point in San Francisco's active permit queue.

State Title 24 vs. San Francisco reach code: The state energy code sets a floor; San Francisco's reach codes set a narrower corridor. A system that satisfies Title 24 prescriptively with a high-efficiency gas furnace may nonetheless require all-electric equipment to satisfy the local reach code. These two compliance layers are not always reconciled cleanly in DBI permit review, and projects occasionally require supplemental documentation to satisfy both.

Refrigerant transition: The CEC's 2022 code cycle began incorporating language anticipating EPA Section 608 low-GWP refrigerant mandates. Equipment using R-410A, the dominant residential refrigerant, faces a manufacturing phasedown beginning in 2025 under EPA rules (EPA HFC phasedown, AIM Act, 2021). Contractors specifying equipment for projects that will not complete construction until 2025–2026 face forward compatibility uncertainty.

Common misconceptions

Misconception: Title 24 compliance is automatic if equipment carries an ENERGY STAR label.
ENERGY STAR certification and Title 24 compliance are separate determinations. ENERGY STAR uses nationally uniform thresholds; Title 24 sets California-specific and climate-zone-specific minimums. In Climate Zone 3, Title 24 may require efficiency ratings that exceed or differ from ENERGY STAR thresholds for the same equipment category.

Misconception: Only new construction requires Title 24 HVAC compliance.
Alterations trigger compliance when they cross defined thresholds. Replacing a duct system, adding conditioned square footage, or changing the HVAC fuel source in an existing building all trigger applicable portions of Title 24. The 2022 California Energy Code explicitly defines alteration thresholds in Sections 141.0 and 150.2.

Misconception: A licensed HVAC contractor can self-certify HERS measures.
HERS field verification must be performed by a rater certified through the CEC's HERS program and registered with a CEC-approved HERS provider. The installing contractor cannot self-verify measures on their own project.

Misconception: Performance compliance means no minimum equipment efficiency requirement.
Even under performance compliance, specific measures remain prescriptively mandatory regardless of the modeling outcome. These include mandatory measures enumerated in Section 110.x of the California Energy Code — thermostat setback capability, duct insulation minimums in certain configurations, and refrigerant charge verification — which cannot be traded away through performance modeling credits.

Misconception: San Francisco's fog-driven mild climate means air conditioning equipment is exempt from Title 24 efficiency requirements.
Cooling equipment installed in Climate Zone 3 buildings must meet SEER2 minimums regardless of whether cooling load is expected to be low. The code applies to installed equipment capacity, not to predicted run-hours.

Checklist or steps (non-advisory)

The following sequence describes the standard Title 24 HVAC compliance workflow as structured by DBI permit requirements and CEC program rules. This is a reference description of the process — not professional advice.

1. Determine applicable code cycle: Confirm whether the 2022 California Energy Code (effective January 1, 2023) or an earlier adopted edition governs the project based on permit application date.

2. Identify occupancy classification and system scope: Classify the building as low-rise residential, high-rise residential, or nonresidential. Identify whether the project is new construction, an alteration, or an addition to determine which sections of Title 24 apply.

3. Select compliance pathway: Choose prescriptive or performance compliance. Mixed-fuel projects (if any are still permissible under San Francisco's reach code) may require separate pathway analysis. Document pathway selection on CEC Compliance Form CF1R (residential) or CF1N (nonresidential).

4. Specify equipment to minimum efficiency standards: For the prescriptive pathway, confirm that all HVAC equipment meets the applicable SEER2, HSPF2, AFUE, EER, or COP minimums for Climate Zone 3 per the 2022 California Energy Code tables.

5. Design duct system to leakage standards: For new systems, target ≤6% total duct leakage; for altered systems, target ≤15%. Document duct routing, insulation R-value, and sealing specifications in permit drawings.

6. Identify required HERS verification measures: List all measures requiring HERS field verification — typically duct leakage, refrigerant charge, fan airflow, and verified refrigerant charge (VRC) — on the CF2R form.

7. Submit permit package to DBI: Include completed CF1R/CF1N, mechanical plans, equipment cut sheets, and any energy modeling output files if using the performance pathway. San Francisco DBI requires plan check approval before installation begins.

8. Schedule HERS rater for field verification: Engage a CEC-certified HERS rater before inspection scheduling. Rater submits field verification data (CF3R) to the approved HERS provider's registry.

9. Pass DBI mechanical inspection: DBI mechanical inspector reviews installation against permit drawings and verified HERS data. Certificate of Occupancy cannot be issued until all mechanical inspection items are cleared.

10. Obtain Certificate of Compliance: The completed CF1R/CF2R/CF3R forms constitute the official record of Title 24 compliance. These must be available on-site and retained for the life of the building per CEC record-keeping requirements.