CALGreen · California Green Building Standards Code (CALGreen)

Which ACCA manuals are required/referenced for residential load, duct and equipment sizing?

Q: Do I have to buy ACCA manuals to comply?

No — the code requires using the methods in § 4.507.2 (Manual J/D/S or equivalent methods such as ASHRAE handbooks or approved software). However, the manual editions cited in the referenced standards list are Manual J–2016, Manual D–2016, Manual S–2014 ; using an equivalent method means you must document equivalence.

Q: Can I use different design temperatures than typical tables?

Yes — § 4.507.2 includes an Exception permitting alternate design temperatures necessary to ensure system function; be prepared to justify them.

Q: Are ASHRAE handbooks allowed instead of ACCA manuals?

Yes — § 4.507.2 permits ASHRAE handbooks or other equivalent design software or methods as alternatives.

Q: Does the Energy Code reference the same manuals?

Yes — the California Energy Code also references ACCA Manual J for loads and Manual S for equipment selection in its mandatory provisions (see referenced standards in the Energy Code).

For a homeowner: California CALGreen requires that HVAC systems be sized using industry load, duct and equipment methods — specifically Manual J for loads, Manual D for ducts, and Manual S for equipment (or ASHRAE/equivalent methods).

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

California CALGreen requires that residential heating and air‑conditioning systems be sized, designed and have equipment selected using recognized methods. The controlling provision is § 4.507.2 — which explicitly directs the use of ANSI/ACCA Manual J for loads, ANSI/ACCA Manual D for ducts, and ANSI/ACCA Manual S for equipment selection (alternatives such as ASHRAE handbooks or equivalent methods are permitted).

Use a proper Manual J load calculation, Manual D duct design, and Manual S equipment selection (or equivalent); that is the rule in § 4.507.2.

Requirements in detail

Which documents are named

Manual J (load calculations) — for establishing heat loss and heat gain. § 4.507.2 references ANSI/ACCA 2 Manual J—2016.
Manual D (duct sizing) — for sizing duct systems. § 4.507.2 references ANSI/ACCA 1 Manual D—2016.
Manual S (equipment selection) — for selecting heating and cooling equipment to meet the calculated loads. § 4.507.2 references ANSI/ACCA 3 Manual S—2014 (Manual S also appears in the California Energy Code references for equipment selection).

Why each is required (short)

Manual J determines the building’s required heating and cooling capacities so equipment isn’t undersized or oversized. § 4.507.2 mandates using Manual J (or ASHRAE/equivalent) to establish heat loss/gain.
Manual D produces the duct layout and sizes needed to deliver the airflows calculated in Manual J while meeting friction/velocity constraints. § 4.507.2 mandates Manual D (or ASHRAE/equivalent) for duct sizing.
Manual S matches the equipment to the load, considering performance at design conditions and installed capacity. § 4.507.2 mandates Manual S (or equivalent) for equipment selection.

Quick decision table

Decision / deliverable	Which ACCA manual (purpose)	Version referenced in code	Code Reference
Establish building heating & cooling loads	ANSI/ACCA 2 Manual J — Residential Load Calculations	Manual J — 2016	§ 4.507.2
Size supply & return ductwork	ANSI/ACCA 1 Manual D — Residential Duct Systems	Manual D — 2016	§ 4.507.2
Select heating/cooling equipment	ANSI/ACCA 3 Manual S — Residential Equipment Selection	Manual S — 2014 (Manual S also appears in CA Energy Code references)	§ 4.507.2

Acceptable alternatives / equivalence

The section allows ASHRAE handbooks or other equivalent design software or methods in lieu of the ACCA manuals; the code does not force only ACCA documents but names them as the specified references. § 4.507.2 (text) explicitly lists ASHRAE handbooks or equivalents as acceptable alternatives.

Exceptions & special cases

Alternate design temperatures: The code includes an Exception allowing use of alternate design temperatures necessary to ensure the systems function (i.e., you may use locally justified design temps different from standard values when required). This exception appears directly in § 4.507.2.
Equivalency: If you use an alternate method, be prepared to show equivalence to Manual J/D/S (documentation in the plans or submittal demonstrating the method’s basis). The code language permits equivalents but does not define an acceptance procedure here — the enforcing agency may require substantiation. § 4.507.2 permits equivalents.

Common mistakes

Relying on rules‑of‑thumb or contractor “thumb‑in‑the‑air” sizing rather than a documented Manual J load calculation (code requires a load method such as Manual J). § 4.507.2.
Selecting equipment by nameplate tonnage without confirming rated capacity at the project design conditions — Manual S is the code‑referenced method for proper selection. § 4.507.2.
Sizing ducts by shop drawings or experience alone without performing a Manual D layout/fitting/friction analysis — the code calls for Manual D (or equivalent). § 4.507.2.
Using outdated industry guides when the code references specific editions (the CALGreen referenced ACCA editions are shown in the referenced standards listing). Check the edition referenced by the adopting document and the enforcing agency.

Worked example — applying the rule with numbers

Steps (as required by § 4.507.2): run Manual J → Manual S → Manual D.

Scenario: single‑family home, 2,000 ft², winter design indoor 68°F, summer design indoor 75°F (typical inputs).

Manual J: calculate loads. Suppose Manual J outputs: Heating design load = 36,000 Btu/h and Cooling design load = 24,000 Btu/h (2.0 tons). (These are the results from running the Manual J procedure for the house geometry, envelope, infiltration, internal gains, and chosen design temps.)
Manual S: select equipment to meet the loads. For Cooling = 24,000 Btu/h, choose an outdoor unit whose net capacity at the site design conditions meets or slightly exceeds 24,000 Btu/h when combined with indoor coil performance and system effects (Manual S guides matching equipment to the Manual J loads and system conditions). Do not simply pick the next larger “rule‑of‑thumb” tonnage without checking rated capacity at the design conditions.
Manual D: size ducts to deliver the required airflow. If the selected equipment requires 800 CFM for cooling at design conditions, run Manual D to size trunk and branch ducts to deliver 800 CFM with acceptable velocities and friction losses, accounting for fittings and branches. The duct layout and sizes must be documented with the Manual D outputs (losses, friction rate, and duct sizes).

Notes: the example numbers are illustrative steps showing the sequence the code requires; § 4.507.2 mandates the methods (Manual J/D/S or equivalent) be used, not the specific numerical values.

Related provisions

§ 4.506.1 — Bathroom exhaust fan requirements (relevant to whole‑house ventilation/IAQ; found near the Environmental Comfort chapter).
§ 4.507.1 — Reserved (contextual location of the Environmental Comfort provisions).
§ 4.508 — Outdoor air quality (reserved in the code table, next section after 4.507).
Referenced standards list (Chapter 6 / referenced organizations) — shows the specific ANSI/ACCA editions the code cites for Manuals J, D and S tied to § 4.507.2.

Code references

Grounded in the retrieved California Green Building Standards Code (CALGreen) — click a citation to read the verbatim passage:

CALGreen § 4.507.2 High relevance — show source text
Suite 300, Arlington, VA 22206
www.acca.org|~~**ACCA~~ Air Conditioning Contractors of America, 2800 Shirlington Road, Suite 300, Arlington, VA 22206
www.acca.org| |ANSI/ACCA 1 Manual D–2016|Residential Duct Systems|4.507.2| |ANSI/ACCA 2 Manual J–2016|Residential Load Calculations|4.507.2| |ANSI/ACCA 3 Manual S–2014|Residential Equipment Selection|4.507.2| |ACI American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439
www.concrete.org|**ACI** American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439
www.concrete.org|**ACI** American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439
www.concrete.org| |ACI CT-21
|Concrete Terminology
|A5.405.5.2.1.1| |~~AHAM Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C. 20026-3627
http://www.aham.org|AHAM Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C. 20026-3627
http://www.aham.org|AHAM Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C. 20026-3627
http://www.aham.org| |ANSI/AHAM DW-1-2010|Household Electric Dishwashers|202| |ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 180 Technology Parkway NW, Peachtree Corners, GA 30092
www.ashrae.org|**ASHRAE**American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 180 Technology Parkway NW, Peachtree Corners, GA 30092
www.ashrae.org|**ASHRAE**American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 180 Technology Parkway NW, Peachtree Corners, GA 30092
www.ashrae.org| |ANSI/ASHRAE
Standard 52.2- 2017
|Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency
by Particle Size
|5.504.1| |ASME~~ American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990
www.asme.org|~~ASME~~ American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990
www.asme.org|~~ASME**~~ American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990
www.asme.org| |ASME A112.18.1|Plumbing Supply Fittings|5.303.6| |ASME A112.19.2|Ceramic Plumbing Fixtures|WS-2| |ASME A112.19.

CALGreen § 6-1 High relevance — show source text

2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 6-1

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6-2 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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6 REFERENCED ORGANIZATIONS AND STANDARDS

SECTION 601—GENERAL

601.1 This chapter lists the organizations and standards that are referenced in various sections of this document. The standards are listed according the promulgating agency of the standard.

STANDARD ACRONYM or NUMBER	STANDARD NAME or TITLE	REFERENCED SECTION
~~AABC ~~Associated Air Balance Council, 1518 K St NW, Washington, DC 20005www.aabc.com	~~AABC ~~Associated Air Balance Council, 1518 K St NW, Washington, DC 20005www.aabc.com	~~AABC ~~Associated Air Balance Council, 1518 K St NW, Washington, DC 20005www.aabc.com
National Standards, 1989	Total System Balance	5.410.4.3.1, A5.410.5.3.1
~~ACCA~~ Air Conditioning Contractors of America, 2800 Shirlington Road, Suite 300, Arlington, VA 22206 www.acca.org	~~ACCA~~ Air Conditioning Contractors of America, 2800 Shirlington Road, Suite 300, Arlington, VA 22206 www.acca.org	~~ACCA~~ Air Conditioning Contractors of America, 2800 Shirlington Road, Suite 300, Arlington, VA 22206 www.acca.org
ANSI/ACCA 1 Manual D–2016	Residential Duct Systems	4.507.2
ANSI/ACCA 2 Manual J–2016	Residential Load Calculations	4.507.2
ANSI/ACCA 3 Manual S–2014	Residential Equipment Selection	4.507.2
ACI American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439 www.concrete.org	ACI American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439 www.concrete.org	ACI American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 48331-3439 www.concrete.org
ACI CT-21	Concrete Terminology	A5.405.5.2.1.1
~~AHAM ~~Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C. 20026-3627 http://www.aham.org	~~AHAM ~~Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C. 20026-3627 http://www.aham.org	~~AHAM ~~Association of Home Appliance Manufacturers, 1119 19th Street NW, Suite 402, Washington, D.C.

CALGreen § 4.507.1 High relevance — show source text

4.507.1 Reserved.

2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 4-17

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RESIDENTIAL MANDATORY MEASURES

4.507.2 Heating and air-conditioning system design. Heating and air-conditioning systems shall be sized, designed and have their equipment selected using the following methods:

The heat loss and heat gain is established according to ANSI/ACCA 2 Manual J—2016 ( Residential Load Calculation ), ASHRAE handbooks or other equivalent design software or methods.
Duct systems are sized according to ANSI/ACCA 1 Manual D—2016 ( Residential Duct Systems ), ASHRAE handbooks or other equivalent design software or methods.
Select heating and cooling equipment according to ANSI/ACCA 3 Manual S—2014 ( Residential Equipment Selection ) or other equivalent design software or methods.

Exception: Use of alternate design temperatures necessary to ensure the systems function are acceptable.

SECTION 4.508—OUTDOOR AIR QUALITY (RESERVED)

4-18 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE

CHAPTER 5 – NONRESIDENTIAL MANDATORY MEASURES

DIVISION 5.1 – PLANNING AND DESIGN

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	OSHPD	Col11	Col12	Col13	Col14	Col15	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting agency	BSC	BSC- CG	SFM	1	2	1/AC	AC	SS	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt entire CA chapter		X
Adopt entire chapter as amended (amended sections listed below)
Adopt only those sections that are listed below								X
Chapter/Section
5.101								X
5.102 Definitions								X
5.105								X
5.105.1 Scope								X
5.106.4.2 and subsections		†						X
5.106.5.6 and subsections		†						X
5.106.

CALGreen § 506.1 High relevance — show source text
ENERGY STAR fans ducted to terminate outside the building.
2. Fans must be controlled by a humidity control (separate or built-
in); OR functioning as a component of a whole-house ventilation
system.
3. Humidity controls with manual or automatic means of
adjustment, capable of adjustment between a relative humidity
range of≤ 50 percent to a maximum of 80 percent.||||
|
|
| |A4.506.1 Reserved.||||||| |A4.506.2 [HR] Provide filters on return air openings rated MERV 8 or
higher during construction when it is necessary to use HVAC
equipment.||||||| |A4.506.3 Direct-vent appliances shall be used when equipment is
located in conditioned space; or the equipment must be installed in
an isolated mechanical room.||||||| |Environmental Comfort||||||| |4.507.2 Duct systems are sized, designed and equipment is selected
using the following methods:
1. Establish heat loss and heat gain values according to ANSI/ACCA 2
Manual J-2016 or equivalent.
2. Size duct systems according to ANSI/ACCA 1 Manual D-2016
or equivalent.
3. Select heating and cooling equipment according to ANSI/ACCA 3
Manual S-2014 or equivalent.||||||| |Outdoor Air Quality
Reserved||||||| |Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions|Innovative Concepts and Local Environmental Conditions| |A4.509.1 Items in this section are necessary to address innovative
concepts or local environmental conditions.||||||| |Item 1||
|
|
|
|
| |Item 2||
|
|
|
|
| |Item 3||||||| |Installer and Special Inspector Qualifications||||||| |Qualifications|Qualifications|Qualifications|Qualifications|Qualifications|Qualifications|Qualifications| |702.1 HVAC system installers are trained and certified in the proper
installation of HVAC systems.||||||| |702.2 Special inspectors employed by the owner or owner's agent
must be qualified and able to demonstrate competence in the
discipline they are inspecting to the enforcing agency.
CALGreen § 390-2021 High relevance — show source text
AHRI Standard 340/360 2022 (I-P) 2022 Standard for Performance Rating of Commercial and Industrial Unitary Air-conditioning and Heat Pump Equipment

ANSI/AHRI Standard 365 (I-P) 2009 Standard for Performance Rating of Commercial and Industrial Unitary Air-Conditioning Condensing Units

ANSI/AHRI Standard 390-2021 (I-P) 2021 Standard for Performance Rating of Single Package Vertical Air-conditioners And Heat Pumps

ANSI/AHRI Standard 400 (I-P) 2015 Standard for Performance Rating of Liquid to Liquid Heat Exchangers

AHRI Standard 420-2023 (I-P) 2023 Standard for Performance Rating of Forced-circulation Free-delivery Unit Coolers

AHRI Standard 430-2020 (I-P) 2020 Standard for Performance Rating of Central Station Air-handling Unit Supply Fans

AHRI Standard 440 (I-P) 2019 Standard for Performance Rating of Fan-coil Units

ANSI/AHRI Standard 460 2005 Standard for Performance Rating of Remote Mechanical-Draft Air-Cooled Refrigerant Condensers

ANSI/AHRI Standard 550/590-2023 2023 Standard for Performance Rating of Water-Chilling and Heat Pump Water-heating Packages Using the Vapor Compression Cycle

AHRI Standard 560-2023 (I-P) 2023 Standard for Performance Rating of Water-cooled Lithium Bromide Absorption Waterchilling and Water-heating Packages

AHRI Standard 680 (I-P) 2017 Standard for Performance Rating of Residential Air Filter Equipment

AHRI Standard 920 (I-P) with Addendum 1 2020 Standard for Performance Rating of Direct Expansion-Dedicated Outdoor Air System Units

AHRI Standard 1060-2023 (I-P) 2023 Standard for Performance Rating of Air-to-Air Exchangers for Energy Recovery Ventilation Equipment

AHRI Standard 1230-2023 (I-P) 2023 Standard for Performance Rating of Variable Refrigerant Flow (VRF) Multi-split Airconditioning and Heat Pump Equipment

AHRI Standard 1240-2017 (R2023) (I-P) 2017 (R2023) Standard for Performance Rating of Active Chilled Beams

AHRI Standard 125 0 2020 Standard for Performance Rating of Walk-in Coolers and Freezers

AHRI Standard 1360-2022 (I-P) 2022 Standard for Performance Rating of Computer and Data Processing Room Air Conditioners

Available from: Air-Conditioning, Heating and Refrigeration Institute 2311 Wilson Blvd., Suite 400 Arlington, VA 22203 (703) 524-8800

2025 CALIFORNIA ENERGY CODE 287

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STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

AIR-CONDITIONING CONTRACTORS OF AMERICA

ANSI/ACCA 2 Manual J-2016 Manual J—Residential Load Calculation, Eighth Edition

ANSI/ACCA 2 Manual S 2023 Manual S—Residential Equipment Selection, Third Edition

Available from: Air-Conditioning Contractors of America, Inc. 2800 Shirlington Road, Suite 300 Arlington, VA 22206 (703) 575-4477

www.acca.org

AMERICAN ARCHITECTURAL MANUFACTURERS ASSOCIATION

CANADIAN STANDARDS ASSOCIATION

WINDOW AND DOOR MANUFACTURERS ASSOCIATION
CALGreen § 1230-2023 High relevance — show source text
AHRI Standard 1230-2023 (I-P) 2023 Standard for Performance Rating of Variable Refrigerant Flow (VRF) Multi-split Airconditioning and Heat Pump Equipment

AHRI Standard 1240-2017 (R2023) (I-P) 2017 (R2023) Standard for Performance Rating of Active Chilled Beams

AHRI Standard 125 0 2020 Standard for Performance Rating of Walk-in Coolers and Freezers

AHRI Standard 1360-2022 (I-P) 2022 Standard for Performance Rating of Computer and Data Processing Room Air Conditioners

Available from: Air-Conditioning, Heating and Refrigeration Institute 2311 Wilson Blvd., Suite 400 Arlington, VA 22203 (703) 524-8800

2025 CALIFORNIA ENERGY CODE 287

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

AIR-CONDITIONING CONTRACTORS OF AMERICA

ANSI/ACCA 2 Manual J-2016 Manual J—Residential Load Calculation, Eighth Edition

ANSI/ACCA 2 Manual S 2023 Manual S—Residential Equipment Selection, Third Edition

Available from: Air-Conditioning Contractors of America, Inc. 2800 Shirlington Road, Suite 300 Arlington, VA 22206 (703) 575-4477

www.acca.org

AMERICAN ARCHITECTURAL MANUFACTURERS ASSOCIATION

CANADIAN STANDARDS ASSOCIATION

WINDOW AND DOOR MANUFACTURERS ASSOCIATION

AAMA/WDMA/CSA 101/I.S.2/A440-22 North American Fenestration Standard/Specification for windows, doors, and skylights

Available from: AAMA 1827 Walden Office Square, Suite 550 Schaumburg, IL 60173-4268 (847) 303-5664 www.aamanet.org

CSA 5060 Spectrum Way, Suite 100 Mississauga, ON, Canada L4W 5N6 (800) 463-6727

www.csagroup.org

WDMA 2025 M Street, NW, Suite 800 Washington, DC 20036-3309 (202) 367-1157 www.wdma.com

AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS

2024 TLVs and BEIs Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices

Available from: ACGIH 1330 Kemper Meadow Drive Cincinnati, Ohio 45240 (513) 742-2020 www.acgih.org

AMERICAN NATIONAL STANDARDS INSTITUTE

ANSI/AMCA Standard 208-18 Calculation of the Fan Energy Index (2018)

ANSI/AMCA Standard 210-16/ASHRAE Standard 51-16 Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating

ANSI/AMCA Standard 220-21 Laboratory Methods of Testing Air Curtain Units for Aerodynamic Performance Rating

ANSI/AMCA Standard 500-D-18 Laboratory Methods of Testing Dampers For Rating

ANSI/ASABE S640 JUL2017 (R2022) Quantities and Units of Electromagnetic Radiation for Plants (Photosynthetic Organisms)

ANSI/ASSP Z9.5-2022 Laboratory Ventilation

ANSI/CTA-2045-B: 2021 Modular Communications Interface for Energy Management
CALGreen § 504.2 High relevance — show source text
504.2**Install VOC compliant resilient flooring systems.
Tier 1. At least 90 percent of the resilient flooring installed shall comply.
**Tier 2.**100 percent of the resilient flooring installed shall comply.||2|2|
|
|
| |A4.504.3Thermal insulation installed in the building shall meet the
following requirements:
Tier 1. Install thermal insulation in compliance with VOC limits.
Tier 2. Install insulation which contains no-added formaldehyde
(NAF) and is in compliance with Tier 1.||2|2|||| |Interior Moisture Control||||||| |4.505.2Vapor retarder and capillary break is installed at slab-on-
grade foundations.||||||| |4.505.3 Moisture content of building materials used in wall and floor
framing is checked before enclosure.||||||| |Indoor Air Quality and Exhaust||||||| |4.506.1 Each bathroom shall be provided with the following:
1. ENERGY STAR fans ducted to terminate outside the building.
2. Fans must be controlled by a humidity control (separate or built-
in); OR functioning as a component of a whole-house ventilation
system.
3. Humidity controls with manual or automatic means of
adjustment, capable of adjustment between a relative humidity
range of≤ 50 percent to a maximum of 80 percent.||||
|
|
| |A4.506.1 Reserved.||||||| |A4.506.2 [HR] Provide filters on return air openings rated MERV 8 or
higher during construction when it is necessary to use HVAC
equipment.||||||| |A4.506.3 Direct-vent appliances shall be used when equipment is
located in conditioned space; or the equipment must be installed in
an isolated mechanical room.||||||| |Environmental Comfort||||||| |4.507.2 Duct systems are sized, designed and equipment is selected
using the following methods:
1. Establish heat loss and heat gain values according to ANSI/ACCA 2
Manual J-2016 or equivalent.
2. Size duct systems according to ANSI/ACCA 1 Manual D-2016
or equivalent.
3. Select heating and cooling equipment according to ANSI/ACCA 3
Manual S-2014 or equivalent.
CALGreen § 160.3 High relevance — show source text
e. Excess outdoor air.

viii. The FDD system shall be certified to the Energy Commission as meeting the requirements of Sections 160.3(a)2Hi through 160.3(a)2Hvii in accordance with Section 110.0 and JA6.3. Exception to Section 160.3(a)2Hviii: FDD algorithms based in direct digital control systems are not required to be certified to the Energy Commission. I. Direct digital controls (DDC). Direct digital controls to the zone shall be provided as specified by Table 160.3-C. i. The provided DDC system shall meet the control logic requirements of Sections 160.3(a)2E and 160.3(a)2G, and be capable of the following: ii. Monitoring zone and system demand for fan pressure, pump pressure, heating and cooling; iii. Transferring zone and system demand information from zones to air distribution system controllers and from air distribution systems to heating and cooling plant controllers; iv. Automatically detecting the zones and systems that may be excessively driving the reset logic and generate an alarm or other indication to the system operator; v. Readily allow operator removal of zone(s) from the reset algorithm; vi. For new buildings, trending and graphically displaying input and output points; and vii. Resetting heating and cooling setpoints in all noncritical zones upon receipt of a signal from a centralized contact or software point as described in Section 160.3(a)2G. J. Optimum start/stop controls. Space-conditioning systems with DDC to the zone level shall have optimum start/stop controls. The control algorithm shall, as a minimum, be a function of the difference between space temperature and occupied setpoint, the outdoor air temperature, and the amount of time prior to scheduled occupancy. Mass radiant floor slab systems shall incorporate floor temperature onto the optimum start algorithm. Exception to Section 160.3(a)2J: Systems that must operate continuously.

(b) Dwelling unit space-conditioning and air distribution systems.
1. Building cooling and heating loads. Building heating and cooling loads shall be determined using a method based on any one of the following, using cooling and heating loads as two of the criteria for equipment sizing and selection: A. The ASHRAE Handbook, Equipment Volume, Applications Volume and Fundamentals Volume; or B. The SMACNA Residential Comfort System Installation Standards Manual; or
C. The ACCA Manual J.

Exception to Section 160.3(b)1: Block loads, the total load for all rooms combined that are served by the central equipment, may be used for the purpose of system sizing for additions. NOTE: Heating systems are required to have a minimum heating capacity adequate to meet the minimum requirements of the CBC.
1. Design conditions . Design conditions shall be determined in accordance with the following: A. For the purpose of sizing the space-conditioning (HVAC) system, the indoor design temperatures shall be 68°F for heating and 75°F for cooling. B. Outdoor design conditions shall be selected from one of the following: i. Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X; or ii. The ASHRAE Handbook Fundamentals Volume; or
iii. The ACCA Manual J.

C. The outdoor design temperatures for heating shall be no lower than the 99.0 percent Heating Dry Bulb or the Heating Winter Median of Extremes values.
CALGreen § 601.0 High relevance — show source text
136 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

CHAPTER 6

DUCT SYSTEMS

601.0 General.

601.1 Applicability. Ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system shall comply with the requirements of this chapter, Chapter 5 for exhaust ducts, and Chapter 7 for combustion air ducts. 601.2 Sizing Requirements. Duct systems shall be sized in accordance with applicable standards in Chapter 18 or by other approved methods.

Exception: Residential duct systems shall be sized in accordance with ACCA Manual D, ACCA Manual Zr, as applicable, or by other approved methods.

601.2.1 California Energy Code Residential Return Duct Sizing Requirements. California Energy Code Tables 150.0-B and 150.0-C specify return duct sizing requirements for single return and multiple return duct systems, respectively, that are applicable as an alternative to confirming system airflow via field verification and diagnostic testing. See California Energy Code Section 150.0(m)13 for provisions applicable to newly con- structed buildings, and Section 150.2(b)(1)(F)(ii)(a) for alterations.

602.0 Material.

602.1 General. Materials used for duct systems shall comply with Section 602.2 through Section 602.7 as applicable. Exception: [OSHPD 1, 1R, 2, 3, 4 & 5] See Section 407.4.2.

[Not permitted for OSHPD 1, 1R, 2, 3, 4 & 5] Concealed building spaces or independent construction within buildings shall be permitted to be used as ducts or plenums. Gypsum board shall not be used for positive pressure ducts.

Exception: In healthcare facilities, concealed spaces shall not be permitted to be used as ducts or plenums.

602.2 Combustibles Within Ducts or Plenums. Materials exposed within ducts or plenums shall be noncombustible or shall have a flame spread index not to exceed 25 and a smoke-developed index not to exceed 50, where tested as a composite product in accordance with ASTM E84 or UL 723. Plastic piping installed in plenums shall be tested in accordance with all requirements of ASTM E84 or UL 723. Mounting methods, supports and sample sizes of materials for testing that are not specified in ASTM E84 or UL 723 shall be prohibited.

Exceptions:

(1) Return-air and outside-air ducts, plenums, or concealed spaces that serve a dwelling unit.

(2) Air filters in accordance with the requirements of Section 311.2.

(3) Water evaporation media in an evaporative cooler.

(4) Charcoal filters where protected with an approved fire suppression system.

(5) Products listed and labeled for installation within plenums in accordance with Section 602.2.1 through Section 602.2.4.

(6) Smoke detectors in accordance with the requirements of Section 609.0.

(7) Duct insulation, coverings, and linings and other supplementary materials installed in accordance with Section 605.0.
CALGreen § 150.0 High relevance — show source text
1. In Climate Zones 14 and 16, a Class I or Class II vapor retarder shall be installed on the conditioned space side of all insulation in all exterior walls, vented attics and unvented attics with air-permeable insulation.
(h) Space-conditioning equipment.
1. Building cooling and heating loads. Building heating and cooling loads shall be determined using a method based on any one of the following: A. The ASHRAE Handbook, Equipment Volume, Applications Volume and Fundamentals Volume; or B. The SMACNA Residential Comfort System Installation Standards Manual; or
C. The ACCA Manual J.

Exception 1 to Section 150.0(h)1: Block loads, the total load for all rooms combined that are served by the central equipment, may be used for the purpose of system sizing for additions. 2. Design conditions. Design conditions shall be determined in accordance with the following: A. For the purpose of sizing the space-conditioning (HVAC) system, the indoor design temperatures shall be 68°F for heating and 75°F for cooling. B. Outdoor design conditions shall be selected from one of the following: i. Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X; or ii. The ASHRAE Handbook, Fundamentals Volume; or

iii. The ACCA Manual J.

C. The outdoor design temperatures for heating shall be no lower than the 99.0 percent Heating Dry Bulb or the Heating Winter Median of Extremes values.

D. The outdoor design temperatures for cooling shall be no greater than the 1.0 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.
1. Outdoor condensing units. A. Clearances. Installed air conditioner and heat pump outdoor condensing units shall have a clearance of at least five (5) feet (1.5 meters) from the outlet of any dryer vent. B. Liquid line drier. Installed air conditioner and heat pump systems shall be equipped with liquid line filter driers if required, as specified by manufacturer’s instructions.
2. Central forced-air heating furnaces. A. Temperature rise. Central forced-air heating furnace installations shall be configured to operate in conformance with the furnace manufacturer’s maximum inlet-to-outlet temperature rise specifications.
3. System selection. A. Equipment sizing and selection shall meet the cooling and heating loads of Sections 150.0(h)1 and 2. B. Systems shall be sized based on ACCA Manual S-2023 in accordance with these requirements: i. Cooling capacity: There is no limit on the minimum capacity. ii. Furnaces: Heating capacity shall be sized based on ACCA Manual S-2023, Table N2.5.
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SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

iii. Heat pump heating capacity: a. Minimum: Heating systems are required to have a heating capacity meeting the minimum requirements of the CBC, not including any supplementary heating. b. Maximum: There is no limit on the maximum heating capacity.
1. Defrost.
CALGreen § 4.506 High relevance — show source text
1. At least three random moisture readings shall be performed on wall and floor framing with documentation acceptable to the enforcing agency provided at the time of approval to enclose the wall and floor framing.
Insulation products which are visibly wet or have a high moisture content shall be replaced or allowed to dry prior to enclosure in wall or floor cavities. Wet-applied insulation products shall follow the manufacturers’ drying recommendations prior to enclosure.

SECTION 4.506—INDOOR AIR QUALITY AND EXHAUST

4.506.1 Bathroom exhaust fans. Each bathroom shall be mechanically ventilated and shall comply with the following:
1. Fans shall be ENERGY STAR compliant and be ducted to terminate outside the building.
2. Unless functioning as a component of a whole house ventilation system, fans must be controlled by a humidity control. a. Humidity controls shall be capable of adjustment between a relative humidity range of ≤ 50 percent to a maximum of 80 percent. A humidity control may utilize manual or automatic means of adjustment. b. A humidity control may be a separate component to the exhaust fan and is not required to be integral (i.e., built-in).
Notes:
1. For the purposes of this section, a bathroom is a room which contains a bathtub, shower or tub/shower combination.
2. Lighting integral to bathroom exhaust fans shall comply with the California Energy Code.
SECTION 4.507—ENVIRONMENTAL COMFORT

4.507.1 Reserved.

2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 4-17

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RESIDENTIAL MANDATORY MEASURES

4.507.2 Heating and air-conditioning system design. Heating and air-conditioning systems shall be sized, designed and have their equipment selected using the following methods:
1. The heat loss and heat gain is established according to ANSI/ACCA 2 Manual J—2016 ( Residential Load Calculation ), ASHRAE handbooks or other equivalent design software or methods.
2. Duct systems are sized according to ANSI/ACCA 1 Manual D—2016 ( Residential Duct Systems ), ASHRAE handbooks or other equivalent design software or methods.
3. Select heating and cooling equipment according to ANSI/ACCA 3 Manual S—2014 ( Residential Equipment Selection ) or other equivalent design software or methods.
Exception: Use of alternate design temperatures necessary to ensure the systems function are acceptable.

SECTION 4.508—OUTDOOR AIR QUALITY (RESERVED)

4-18 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE

CHAPTER 5 – NONRESIDENTIAL MANDATORY MEASURES

DIVISION 5.1 – PLANNING AND DESIGN

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CALGreen § 4.1 High relevance — show source text
4.1||||||||||†||†|†|†|†|||||||||| |603.4.1.1||||||||||X||X|X|X|X|||||||||| |603.9.2||||†|†|||||||||||||||||||| |603.9.2.1|||||||||||||||||||||X|||| |605.1||||||||||X|X|X|X|X|X|||||||||| |605.2||||||||||X|||X|X|X|||||||||| |605.3||||||||||X||X||X|X|||||||||| |606.1||||X|X|||||||||||||||||||| |606.4.1|||X|||||||||||||||||||||| |607.1.1||||||||||X|X|X|X|X|X|||||||||| |609.1|||X|||||||||||||||||||||| |609.1.1|||X|||||||||||||||||||||| |609.2|||X||||||||||||||||||||||

This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

2025 CALIFORNIA MECHANICAL CODE 135

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

136 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

CHAPTER 6

DUCT SYSTEMS

601.0 General.

601.1 Applicability. Ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system shall comply with the requirements of this chapter, Chapter 5 for exhaust ducts, and Chapter 7 for combustion air ducts. 601.2 Sizing Requirements. Duct systems shall be sized in accordance with applicable standards in Chapter 18 or by other approved methods.

Exception: Residential duct systems shall be sized in accordance with ACCA Manual D, ACCA Manual Zr, as applicable, or by other approved methods.

601.2.1 California Energy Code Residential Return Duct Sizing Requirements. California Energy Code Tables 150.0-B and 150.0-C specify return duct sizing requirements for single return and multiple return duct systems, respectively, that are applicable as an alternative to confirming system airflow via field verification and diagnostic testing. See California Energy Code Section 150.0(m)13 for provisions applicable to newly con- structed buildings, and Section 150.2(b)(1)(F)(ii)(a) for alterations.

602.0 Material.

602.1 General. Materials used for duct systems shall comply with Section 602.2 through Section 602.7 as applicable. Exception: [OSHPD 1, 1R, 2, 3, 4 & 5] See Section 407.4.2.

Frequently asked questions

Do I have to buy ACCA manuals to comply?

No — the code requires using the methods in § 4.507.2 (Manual J/D/S or equivalent methods such as ASHRAE handbooks or approved software). However, the manual editions cited in the referenced standards list are Manual J–2016, Manual D–2016, Manual S–2014; using an equivalent method means you must document equivalence.

Can I use different design temperatures than typical tables?

Yes — § 4.507.2 includes an Exception permitting alternate design temperatures necessary to ensure system function; be prepared to justify them.

Which comes first: equipment selection or load calc?

Load calculation (Manual J) always comes first, then equipment selection (Manual S), then duct sizing (Manual D) to match the selected equipment and required airflow — the sequence follows the methods named in § 4.507.2.

Are ASHRAE handbooks allowed instead of ACCA manuals?

Yes — § 4.507.2 permits ASHRAE handbooks or other equivalent design software or methods as alternatives.

Does the Energy Code reference the same manuals?

Yes — the California Energy Code also references ACCA Manual J for loads and Manual S for equipment selection in its mandatory provisions (see referenced standards in the Energy Code).

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