CALGreen · California Green Building Standards Code (CALGreen)

What are the mandatory indoor air quality, exhaust and moisture control measures?

Homeowners: CALGreen requires an ENERGY STAR bathroom fan that vents outdoors and is controlled by an adjustable humidity sensor (unless you have whole‑house ventilation). It also requires slab and framing moisture controls — do not enclose framing over **19%** moisture and follow the code’s capillary‑break options — and requires residential HVAC to be sized and ducts/equipment selected using accepted Manuals (Manual J, D, S).

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Last reviewed: July 6, 2026

What the code requires — plain English

CALGreen requires that each bathroom have a mechanically ventilating ENERGY STAR exhaust fan that vents outdoors and (unless the fan is part of a whole‑house ventilation system) is controlled by a humidity control adjustable from ≤ 50% to 80% (§ 4.506.1). For moisture control CALGreen includes slab and framing moisture controls (see slab vapor retarder / capillary break and framing moisture‑content verification), and mechanical systems must be sized and selected using recognized residential HVAC methods (ANSI/ACCA Manual J, D, and S) (§ 4.507.2; see also the slab and framing rules in 4.505.2–4.505.3).

The single most important practical rule: each bathroom must have an ENERGY STAR exhaust fan that vents outside and is controlled by an adjustable humidity control (unless it’s served by whole‑house ventilation). § 4.506.1.

Requirements in detail

Bathroom exhaust — mandatory

  • Each bathroom (a room containing a bathtub, shower or tub/shower) must be mechanically ventilated. Fans must be ENERGY STAR compliant and ducted to terminate outside the building. § 4.506.1.
  • Control requirement: unless the bathroom fan functions as part of a whole‑house ventilation system, the fan must be controlled by a humidity control. The humidity control may be separate from the fan (not required to be integral), and must be adjustable between ≤ 50% and 80% RH (manual or automatic). § 4.506.1.

Indoor moisture control — mandatory items available in Chapter 4

  • Slab vapor retarder & capillary break: Slab‑on‑grade floors that are already required by the CBC/CRC to have a vapor retarder must also comply with CALGreen’s additional capillary‑break requirements. One accepted method is a 4‑inch (101.6 mm) compacted base of 1/2‑inch (12.7 mm) or larger clean aggregate with the vapor retarder in direct contact with the concrete. Other equivalent methods approved by the enforcing agency or a licensed design professional’s slab design are allowed. § 4.505.2 / 4.505.2.1.
  • Framing moisture content before enclosure: Wall and floor framing shall not be enclosed when framing members exceed 19% moisture content. Moisture must be measured with a probe‑type or contact‑type moisture meter at a point 2 ft to 4 ft from the grade‑stamped end of the member, and at least three random readings must be performed and documented for approval to enclose. Insulation that is visibly wet or has high moisture content must be replaced or allowed to dry prior to enclosure. § 4.505.3.

HVAC design / environmental comfort — mandatory

  • Heating and air‑conditioning systems for residential occupancies must be sized and designed using established methods: determine heat loss/gain with ANSI/ACCA Manual J—2016 (or ASHRAE handbooks/equivalent), size ducts per ANSI/ACCA Manual D—2016, and select equipment per ANSI/ACCA Manual S—2014 (or equivalents). § 4.507.2. (Exception: use of alternate design temperatures when necessary is permitted.)

Quick decision table (values and where to look)

Measure Key value / action Applicability / when to use Code Reference
Bathroom exhaust fan ENERGY STAR; duct to outdoors Every bathroom (tub/shower present) § 4.506.1
Humidity control for bathroom fans Adjustable ≤ 50% to 80% RH; manual or automatic; may be separate component Required unless fan is part of whole‑house ventilation § 4.506.1
Slab capillary break 4 in. base of 1/2 in. or larger clean aggregate OR equivalent method Slab‑on‑grade requiring vapor retarder under CBC/CRC § 4.505.2 / 4.505.2.1
Framing moisture limit before enclosure 19% maximum moisture content; measurements 2–4 ft from grade end; ≥3 random readings documented Before enclosing wall/floor framing § 4.505.3
HVAC sizing & equipment selection Use Manual J (heat loss/gain), Manual D (ducts), Manual S (equipment selection) New residential HVAC design / replacement § 4.507.2

Exceptions & special cases

  • The bathroom fan humidity control requirement does not apply if the fan is functioning as a component of a whole‑house ventilation system; in that case the whole‑house system controls ventilation per its design. § 4.506.1.
  • For the capillary break, the code allows “other equivalent methods approved by the enforcing agency” or a slab design by a licensed design professional in lieu of the 4‑inch aggregate method. § 4.505.2.1.
  • For HVAC design, CALGreen accepts equivalent design software or methods to ANSI/ACCA Manuals; and the code explicitly permits alternate design temperatures when needed to ensure system function. § 4.507.2.

If you need compliance documentation for specific appliances or materials (e.g., ENERGY STAR certification, moisture‑meter logs, Manual J/D/S reports), the enforcing agency will typically require those at plan check or final approval (see the verification requirements in the CALGreen matrices and appendices).

Common mistakes

  • Installing a fan that is not ducted to the outside (terminating into attics or soffits instead of outdoors). § 4.506.1.
  • Using a non‑ENERGY STAR bathroom fan where required. § 4.506.1.
  • Relying on a fan without a humidity control (or one that cannot be adjusted to the ≤ 50%–80% RH range) when not using whole‑house ventilation. § 4.506.1.
  • Enclosing framing with moisture readings above 19%, or failing to document the three required random readings at the specified location 2–4 ft from the grade end. § 4.505.3.
  • Specifying HVAC equipment without producing a Manual J / Manual D / Manual S (or equivalent) calculation package for system sizing/selection. § 4.507.2.

Worked example — single‑family bathroom + framing check

Scenario: New single‑family house with one main bathroom containing a shower. Wall/floor framing about to be enclosed; HVAC being designed.

  1. Bathroom exhaust:

    • Select an ENERGY STAR bathroom fan rated for the expected airflow. Install the fan with a rigid/insulated duct that terminates outside (not into attic). Add a humidity control (stand‑alone control wired to the fan) set to turn on at 60% RH and off at a lower setpoint (within the allowed ≤ 50%–80% range). This satisfies § 4.506.1.

  2. Framing moisture check:

    • Before drywall, take ≥3 random moisture readings of wall studs using a probe meter 2–4 ft from the grade‑stamped end. Measured results: 12%, 16%, 21%.
    • Because one reading is 21% (>19%), you must not enclose that framing member. Remove/replace or allow drying and re‑check. This follows § 4.505.3.

  3. HVAC design:

    • A Manual J calculation (or equivalent) determines a cooling load of 36,000 Btu/h (3 ton) for the home. Use Manual D to size ducts to deliver the required flows without excessive friction/pressure drop, then use Manual S to select equipment that meets the calculated loads and operating conditions. Document the Manuals’ output on the plans per § 4.507.2. (If an alternate design temperature is required for the local microclimate, document and justify it under the § exception.)

Related provisions (in CALGreen)

  • § 4.506.1 — Bathroom exhaust fans (primary IAQ/exhaust rule)
  • § 4.505.2 — Concrete slab foundations: vapor retarder and capillary break requirements
  • § 4.505.3 — Moisture content verification for wall and floor framing (19% limit, measurement points, documentation)
  • § 4.507.2 — Heating and air‑conditioning system design: use Manual J, D, S (or equivalents)
  • § 5.504.5 — Filters in mechanically ventilated nonresidential buildings (MERV 13 requirement) — related to building filtration and IAQ (nonresidential)
  • Appendix A4.506.2 — Construction filters (provide MERV 8 on return air openings during construction) — voluntary/residential appendix guidance

Code references

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

  • 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.

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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 § 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 § 4.506 High relevance — show source text

    Indoor Air Quality And Exhaust 4.506, 5.506 Bathroom exhaust fans 4.506.1 Carbon dioxide monitoring 5.506.2 Carbon dioxide (CO 2 ) monitoring in classrooms 5.506.3

    Filters 5.504.5, A4.506.1 Outside air delivery 5.506.1 Indoor Moisture Control 4.505, 5.505.1 Concrete slab foundations 4.505.2

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    INDEX

    Appendix A6.1 (OSHPD), Table A5.504.8.5 Covering of duct openings and protection of mechanical equipment during construction 4.504.1, 5.504.3 Environmental tobacco smoke control 5.504.7, Appendix A6.1 (OSHPD), A5.504.9 Finish material pollutant control 4.504.2, 5.504.4 Hazardous particulates and chemical pollutants A5.504.5 Indoor air quality (IAQ) during construction 5.504.1, A5.504.1 IAQ Post-construction A5.504.2 Paints and coatings 4.504.2.2, 5.504.4.3 Resilient flooring systems 4.504.4, 5.504.4.6, A4.504.2, A5.504.4.7 Thermal insulation 5.504.4.7, A4.504.3,

    A5.504.4.8

    Product GWP Limits Table 5.409.3

    Referenced Organizations and Standards Chapter 6 Renewable Energy A5.211

    Site Development 4.106, 5.106, A4,106, A5.106 Bicycle parking and changing rooms 5.106.4, A5.106.4.3, Table A5.106.4.3 Bird friendly building design A5.107 Building orientation Appendix A6.1 (OSHPD), A5.106.9 Designated parking for clean air vehicles A5.106.5.1 Exterior wall shading A5.106.7 Grading and paving 4.106.3, 5.106.10 Heat island effect – cool roof Tables A4.106.5(1) – (4), A5.106.11.2, Table

  • CALGreen § 504.1 High relevance — show source text

    APPENDIX A4-28 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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    APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES

    SECTION A4.602—RESIDENTIAL OCCUPANCIES APPLICATION CHECKLIST—continued

    FEATURE OR MEASURE LEVELS
    APPLICANT TO SELECT ELECTIVE MEASURES    		 Col3 Col4 VERIFICATIONS
    ENFORCING AGENCY TO SPECIFY
    VERIFICATION METHOD    		 Col6 Col7
    FEATURE OR MEASURE Mandatory Prerequisites and electives1 Prerequisites and electives1 Enforcing
    Agency

    All    		 Installer or
    Designer

    All    		 Third
    party

    All
    FEATURE OR MEASURE Mandatory Tier 1 Tier 2 Tier 2 Tier 2 Tier 2
    A4.504.1Use composite wood products made with either California
    Air Resources Board approved no-added formaldehyde (NAF) resins
    or ultra-low emitting formaldehyde (ULEF) resins.


    A4.504.2Install 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.
  • CALGreen § 403.3 High relevance — show source text

    ENERGY STAR equipment and appliances Appendix A6.1(OSHPD), A4.403.3, A5.204.1 General 4.201, 5.201, A5.201 Performance approach A4.203, A5.203 Outdoor lighting A5.203.1.1.1 Prescriptive approach Appendix A6.1(OSHPD), 203.3.1.2 Alterations to existing buildings A4.204.1, A4.204.1.2, A5.204.1,

    A5.204.1.1 Energy Efficient Steel Framing A5.213 Environmental Comfort 4.507, 5.507,

    A5.507

    Acoustical control A4.507, A5.507.5 Daylight A5.507.2 Lighting and thermal comfort controls A5.507.1

    Views A5.507.3

    Fireplaces 4.503, 5.503 Foundation Systems A4.403 Frost protected foundation systems A4.403.1

    Reduction in cement use A4.403.2 Framing, Energy Efficient Steel A5.213 Framing Techniques, Efficient A4.404, A5.404 Building systems A4.404.3 Lumber size A4.404.1

    Pre-cut materials and details A4.404.4 Wood framing A5.404.1

    Green Building Chapter 3 Mixed occupancy buildings 302 Phased projects 303 Voluntary tiers 304, 305 Voluntary measures 306

    HVAC Design, Equipment and Installation Appendix A6.1 (OSHPD), A5.207

    Indoor Air Quality And Exhaust 4.506, 5.506 Bathroom exhaust fans 4.506.1 Carbon dioxide monitoring 5.506.2 Carbon dioxide (CO 2 ) monitoring in classrooms 5.506.3

    Filters 5.504.5, A4.506.1 Outside air delivery 5.506.1 Indoor Moisture Control 4.505, 5.505.1 Concrete slab foundations 4.505.2

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    INDEX

    Appendix A6.1 (OSHPD), Table A5.504.8.5 Covering of duct openings and protection of mechanical equipment during construction 4.504.1, 5.504.3 Environmental tobacco smoke control 5.504.7, Appendix A6.1 (OSHPD), A5.504.9 Finish material pollutant control 4.504.2, 5.504.4 Hazardous particulates and chemical pollutants A5.504.5 Indoor air quality (IAQ) during construction 5.504.1, A5.504.1 IAQ Post-construction A5.504.2 Paints and coatings 4.504.2.2, 5.504.4.3 Resilient flooring systems 4.504.4, 5.504.4.6, A4.504.2, A5.504.4.7 Thermal insulation 5.504.4.7, A4.504.3,

    A5.504.4.8

  • CALGreen § 5.5 High relevance — show source text

    5**
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Verification of compliance|5.504.4.8.1||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Filters (with exceptions)|5.504.5||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Filters: labeling|5.504.5.1||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Environmental tobacco smoke (ETS) control|5.504.7||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Indoor moisture control|5.505.1||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Outside air delivery|5.506.1|||||

    2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A5-59

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    APPENDIX A5 — NONRESIDENTIAL VOLUNTARY MEASURES

    CHAPTER 5
    DIVISIONS    		 Col2 Col3 SECTION TITLE CODE
    SECTION    		 Y N O PLAN SHEET,
    SPEC OR
    ATTACH
    (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 Mandatory Carbon dioxide (CO2) monitoring 5.506.2
    (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 Mandatory Carbon dioxide (CO2) monitoring in classrooms 5.506.3
    (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 (continued)
    DIVISION 5.5
    Environmental
    Quality
    Select Three Electives    		 Mandatory Acoustical control (with exception) 5.507.4
    (continued)
    **DIVISION 5.
  • CALGreen § 506.1 High relevance — show source text

    See California Department of Public Health’s website for certification programs and testing labs.

    https://www.cdph.ca.gov/Programs/CCDPHP/DEODC/EHLB/IAQ/Pages/VOC.aspx

    Tier 2. Install insulation which complies with Tier 1 plus does not contain any added formaldehyde.

    Note: Documentation must be provided that verifies the materials are certified to meet the pollutant emission limits in this section.

    SECTION A4.505—INTERIOR MOISTURE CONTROL (RESERVED)

    SECTION A4.506—INDOOR AIR QUALITY AND EXHAUST

    A4.506.1 Reserved.

    A4.506.2 Construction filter. [HR] Provide filters on return air openings rated at MERV 8 or higher during construction.

    A4.506.3 Direct-vent appliances. Direct-vent heating and cooling equipment shall be utilized if the equipment will be located in the conditioned space or install the space heating and water heating equipment in an isolated mechanical room.

    2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A4-19

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    APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES

    SECTION A4.507—ENVIRONMENTAL COMFORT (RESERVED)

    SECTION A4.508—OUTDOOR AIR QUALITY (RESERVED)

    SECTION A4.509 —INNOVATIVE CONCEPTS AND LOCAL ENVIRONMENTAL CONDITIONS

    A4.509.1 Innovative concepts and local environmental conditions. The provisions of this code are not intended to prevent the use of any alternate material, appliance, installation, device, arrangement, method, design or method of construction not specifically prescribed by this code. This code does not limit the authority of city, county, or city and county government to make necessary changes to the provisions contained in this code pursuant to Section 101.7.1.

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    A4 RESIDENTIAL VOLUNTARY MEASURES

    DIVISION A4.6 – TIER I AND TIER 2

    SECTION A4.601—GENERAL

    A4.601.1 Scope. The measures contained in this appendix are not mandatory unless adopted by a city, county, or city and county as specified in Section 101.7. The provisions of this section outline means of achieving enhanced construction or reach levels by incorporating additional green building measures. In order to meet one of the tier levels designers, builders or property owners are required to incorporate additional green building measures necessary to meet the threshold of each level.

    A4.601.2 Prerequisite measures. Tier 1 and Tier 2 thresholds require compliance with the mandatory provisions of this code and incorporation of the required prerequisite measures listed in Section A4.601.4.2 for Tier 1 and A4.601.5.2 for Tier 2. Prerequisite measures are also identified in the Residential Occupancies Application Checklist in Section A4.602.

  • CALGreen § 504.4.5.3 High relevance — show source text

    504.4.5.3||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Resilient flooring systems|5.504.4.6||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Resilient flooring: verification of compliance|5.504.4.6.1||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Thermal insulation|5.504.4.7||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Verification of compliance|5.504.4.8.1||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Acoustical ceilings and wall panels|5.504.4.8||||| |DIVISION 5.5
    Environmental
    Quality
    (continued)|Mandatory|Verification of compliance|5.504.4.8.1|||||

    APPENDIX A5-46 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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    APPENDIX A5 — NONRESIDENTIAL VOLUNTARY MEASURES

    CHAPTER 5
    DIVISIONS    		 Col2 SECTION TITLE CODE
    SECTION    		 Y N/A O PLAN SHEET,
    SPEC OR
    ATTACH
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Filters (with exceptions) 5.504.5
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Filters: labeling 5.504.5.1
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Environmental tobacco smoke (ETS) control 5.504.7
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Indoor moisture control 5.505.1
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Outside air delivery 5.506.1
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Carbon dioxide (CO2) monitoring 5.506.2
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Carbon dioxide (CO2) monitoring in classrooms 5.506.3
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Acoustical control (with exception) 5.507.4
    (continued)
    DIVISION 5.5
    Environmental
    Quality    		 Mandatory Exterior noise transmission, prescriptive method
    (with exceptions)    		 5.507.4.
  • CALGreen § 5.504.4.7 High relevance — show source text

    5.504.4.7 Thermal insulation . Comply with the requirements of the California Department of Public Health, “Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers,” Version 1.2, January 2017 (Emission testing method for California Specification 01350).

    See California Department of Public Health’s website for certification programs and testing labs. https://www.cdph.ca.gov/Programs/CCDPHP/DEODC/EHLB/IAQ/ Pages/VOC.aspx#material

    5.504.4.7.1 Verification of compliance. Documentation shall be provided verifying that thermal insulation materials meet the pollutant emission limits.

    5.504.4.8 Acoustical ceilings and wall panels . Comply with the requirements of the California Department of Public Health, “Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers,” Version 1.2, January 2017 (Emission testing method for California Specification 01350).

    See California Department of Public Health’s website for certification programs and testing labs. https://www.cdph.ca.gov/Programs/CCDPHP/DEODC/EHLB/IAQ/Pages/VOC.aspx#material

    5.504.4.8.1 Verification of compliance. Documentation shall be provided verifying that acoustical finish materials meet the pollutant emission limits.

    5.504.5 Filters. In mechanically ventilated buildings, provide regularly occupied areas of the building with air filtration media for outside and return air that provides at least a Minimum Efficiency Reporting Value (MERV) of 13. MERV 13 filters shall be installed prior to occupancy, and recommendations for maintenance with filters of the same value shall be included in the operation and maintenance manual.

    Exception: Existing mechanical equipment.

    5.504.5.1 Labeling. Installed filters shall be clearly labeled by the manufacturer indicating the MERV rating.

    5.504.6 Reserved.

    5.504.7 Environmental tobacco smoke (ETS) control. Where outdoor areas are provided for smoking, prohibit smoking within 25 feet of building entries, outdoor air intakes and operable windows and within the building as already prohibited by other laws or

    2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 5-35

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

    NONRESIDENTIAL MANDATORY MEASURES

    regulations; or as enforced by ordinances, regulations or policies of any city, county, city and county, California Community College, campus of the California State University, or campus of the University of California, whichever are more stringent. When ordinances, regulations or policies are not in place, post signage to inform building occupants of the prohibitions.

    SECTION 5.505—INDOOR MOISTURE CONTROL

    5.505.1 Indoor moisture control. Buildings shall meet or exceed the provisions of California Building Code, CCR, Title 24, Part 2, Sections 1202 (Ventilation) and Chapter 14 (Exterior Walls). For additional measures, see Section 5.407.2 of this code.

    SECTION 5.506—INDOOR AIR QUALITY

  • CALGreen § 5.504.5 High relevance — show source text

    5**
    Environmental
    Quality|Mandatory|Filters (with exceptions)|5.504.5||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Filters: labeling|5.504.5.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Environmental tobacco smoke (ETS) control|5.504.7||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Indoor moisture control|5.505.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Outside air delivery|5.506.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Carbon dioxide (CO2) monitoring|5.506.2||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Carbon dioxide (CO2) monitoring in classrooms|5.506.3||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Acoustical control (with exception)|5.507.4||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Exterior noise transmission, prescriptive method
    (with exceptions)|5.507.4.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Noise exposure where noise contours are not readily
    available|5.507.4.1.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Performance method|5.507.4.2||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Site features|5.507.4.2.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Documentation of compliance|5.507.4.2.2||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Interior sound transmission (with note)|5.507.4.3||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Ozone depletion and greenhouse gas reductions|5.508.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Chlorofluorocarbons (CFCs)|5.508.1.1||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Halons|5.508.1.2||||| |(continued)
    DIVISION 5.5
    Environmental
    Quality|Mandatory|Supermarket refrigerant leak reduction for retail food
    stores 8,000 square feet or more|5.508.

  • CALGreen § 4.505.2 High relevance — show source text

    4.505.2 Concrete slab foundations. Concrete slab foundations required to have a vapor retarder by the California Building Code, Chapter 19 or concrete slab-on-ground floors required to have a vapor retarder by the California Residential Code, Chapter 5, shall also comply with this section.

    4.505.2.1 Capillary break. A capillary break shall be installed in compliance with at least one of the following:

    1. A 4-inch-thick (101.6 mm) base of [1] / 2 inch (12.7 mm) or larger clean aggregate shall be provided with a vapor retarder in direct contact with concrete and a concrete mix design, which will address bleeding, shrinkage and curling, shall be used. For additional information, see American Concrete Institute, ACI 302.2R-06.

    2. Other equivalent methods approved by the enforcing agency.

    3. A slab design specified by a licensed design professional.

    4.505.3 Moisture content of building materials. Building materials with visible signs of water damage shall not be installed. Wall and floor framing shall not be enclosed when the framing members exceed 19 percent moisture content. Moisture content shall be verified in compliance with the following:

    1. Moisture content shall be determined with either a probe-type or contact-type moisture meter. Equivalent moisture verification methods may be approved by the enforcing agency and shall satisfy requirements found in Section 101.8 of this code.

    2. Moisture readings shall be taken at a point 2 feet (610 mm) to 4 feet (1219 mm) from the grade stamped end of each piece to be verified.

    3. 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

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

    RESIDENTIAL MANDATORY MEASURES

  • CMC § 2025 High relevance — show source text

    The building’s structural stability is protected by the regulations for cutting and notching of structural members.

    Chapter 4 Ventilation Air. Chapter 4 regulates the minimum requirements for ventilation air supply, exhaust, and makeup air for occupiable spaces within a building. Building ventilation is one important factor affecting the relationship between airborne transmission of respiratory infections and the health and productivity of workers. Ventilation air may be composed of mechanical or natural ventilation, infiltration, recirculated air, transfer air, or a suitable combination of these. Providing a comfortable and healthy indoor environment for building occupants is of primary concern. When determining ventilation rates, typical and unusual significant sources of indoor pollution need to be controlled. Areas such as kitchens, bathrooms, and laundries are all built to allow specific functions. These spaces produce pollutants such as moisture, odors, volatile organic compounds, particles, or combustion byproducts. The purpose of local exhaust is to control concentrates of these pollutants in the room into which they were emitted and to reduce the spread of pollutants into other parts of the occupancy. Local exhaust ventilation is the source control for pollution that is expected in certain rooms. Using local exhaust to extract contaminants before they mix with the indoor environment is essential.

    Chapter 5 Exhaust Systems. Chapter 5 regulates the minimum requirements for exhaust systems. Chapter 5 contains two parts: Part I provides exhaust requirements for environmental air ducts and product conveying systems; Part II provides exhaust requirements for commercial hoods and kitchen ventilation. Environmental air ducts include exhaust ducts used for transporting the air from domestic kitchens, bathrooms, shower rooms, locker rooms, janitor’s closets, and clothes dryers. Systems that carry nonabrasive exhaust, such as smoke, moderate abrasives such as sawdust, and high abrasives such as manganese or acid vapors use product-conveying ducts. Part II provides the minimum fire safety requirements related to the design, installation, inspection, and maintenance of grease-type operations, such as cooking, for both fuel-gas and solid fuel. Cooking produces a significant amount of smoke, fumes, vapors, heat, and other pollutants. Therefore, acceptable kitchen ventilation is necessary to prevent fires from the build-up of grease and to provide the occupants protection from smoke, unpleasant odors, pollutants, and dangerous gases. There are two types of exhaust hoods (Type I and Type II) used in commercial kitchen applications.

    xiv 2025 CALIFORNIA MECHANICAL CODE

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

    FORMAT OF THE UNIFORM MECHANICAL CODE

    Type I hoods are intended to be installed above equipment or appliances that generate grease or smoke. Type II hoods are intended to be installed above equipment or appliances that generate steam, vapor, heat, or odors and do not generate grease or smoke.

    Chapter 6 Duct Systems. Chapter 6 regulates requirements for ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system. This chapter contains material and installation requirements for metal, gypsum, factory-made, flexible, and plastic ducts. It also contains provisions for duct insulation, dampers, fire protection, and automatic shutoff for the building’s air distribution system. It is worth noting that exhaust ducts are regulated by Chapter 5, and combustion air ducts are regulated by Chapter 7.

  • CALGreen § 120.10 High relevance — show source text

    4(f)2 Variable Air volume (VAV) 120.10(a), 140.4(c)2, 140.4(d), 140.9(c)4, 141.0(a)2, 141.0(b)3, 160.2(c)7, 170.2(c)4A, 170.2(c)4B, Table 170.2-B, Table 170.2-C, Table 180.2-D Capacity heat pump (VCHP) 150.1(b)3, 170.1(d)2 Exhaust 140.9(c)3 Flow control 140.4(k)6, 160.3(d), 170.2(c)4I Fluid flow 140.4(k)1, 170.2(c)4I Speed 120.6(a), 120.6(b)5 Speed compressor 120.6(a)3, 120.6(a)7, 150.0(m)13, 160.3(b)5L Speed control 140.4(k)6, 140.9(b) Speed drive 120.6(e), 120.9(b), 140.4(c)1, 140.4(k)6, 160.4(e), 170.2(c)4I Speed fan 120.6(a)4, 120.6(a)8, 120.6(b)1, 150.0(o), 160.2(b)2 Ventilation 150.0(o), 160.2(b)2A Vending Machine 140.6(a)3J, K, L Vent Damper 110.2(d), 110.2(f) Vented Attic 150.0(a), 150.0(g), 150.2(b)1J, 160.1(a), 160.1(d), 180.2(b)1 Vented Range Hood 150.0(o), Table 150.0-E, 150.0(v), 160.2(b)2B, Table 160.2-E Ventilated Attic 150.1(c)9, 170.2(c), 180.2(a)1 Ventilation 120.1, 140.4(b)4, 150.0(o), 160.3(d)2 Air 120.1(d), 120.2(e), 130.1(f), 140.4(e), 140.4(m), 140.9(b), 150.0(o), 150.1(b), 150.2(a)2C, 160.2(b)2B, 160.2(c), 160.5(b), 170.1(d), 170.2(c), 180.1(a), 180.3(a) And indoor air quality 120.1, 150.0(o), 160.2(b)2 Cooling 150.1(b)3, 150.1(c)12, 150.2(a), 170.1(d) Dampers 150.0(m)8, 160.3(b) Device 10-103(b), 120.1(d), 160.2(c)5 Doors 120.6(f) Fan 120.6(f), 150.2(b)1L, 180.2(b) Load 140.4(b)4, 170.2(c) Only 120.1(h)

  • CALGreen § 1-5 Medium relevance — show source text

    102 Construction Documents

    and Installation Verification . . . . . . . . . . . . . . . . . . . .1-5

    103 Building Standards Commission. . . . . . . . . . . . . . . . . . .1-5 104 Department of Housing and Community Development. . . . . . . . . . . . . . . . . .1-6 105 Division of the State Architect . . . . . . . . . . . . . . . . . . . . .1-6

    106 Office of Statewide Health Planning and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6

    CHAPTER 2 DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

    201 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

    202 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

    CHAPTER 3 GREEN BUILDING . . . . . . . . . . . . . . . . . . . . . . . . 3-3

    301 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

    302 Mixed Occupancy Buildings . . . . . . . . . . . . . . . . . . . . . . .3-4 303 Phased Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4 304 Voluntary Tiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4 305 CALGreen Tier 1 and CALGreen Tier 2 . . . . . . . . . . . . . .3-4

    306 Voluntary Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

    CHAPTER 4 RESIDENTIAL MANDATORY MEASURES . . . . . . 4-3

    4.1 Planning and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3 4.2 Energy Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7 4.3 Water Efficiency and Conservation . . . . . . . . . . . . . . . . .4-9 4.4 Material Conservation and Resource Efficiency . . . . 4-11 4.5 Environmental Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

    CHAPTER 5 NONRESIDENTIAL MANDATORY MEASURES . . 5-3

  • CALGreen § 120.4 Medium relevance — show source text

    120.4(a), 140.4(c), 140.4(e), 140.4(f), 140.4(n),

    Shut-off 120.2(g), 120.6(d), 120.9(a), 130.1(c), 130.4(a), 130.5(d), 140.4(n), 160.3(a), 160.4(e), 160.5(b), 160.5(e), 160.6(d), 170.2(c) Shut-Off and Reset 120.2(e), 160.3(a)2 Sidelit Daylit Zone 130.1(d), 140.3(a)5, 140.3(c), 140.6(a), Table 140.6-A, 160.5(b)4D, 170.2(a)3, 170.2(b), 170.2(e) Siding 150.2(a)1B, 180.1(a) Sign 130.2(b), 140.7(a), 140.7(c) Double-faced signs 140.8(a), 170.2(e)7 Electronic Message Center (EMC) 110.12(d), 130.3(a), 140.8(b)6, 160.5(d) Externally illuminated sign 140.8(a), 140.8(b)6, 141.0, 141.0(b)2F, G, H, 141.0(b)2M, N, O, 170.2(e)7, 180.0, 180.2(b)4 Internally illuminated sign 140.8(a), 140.8(b)6, 141.0(b)2F, G, H, 141.0(b)2M, N, O, 150.0(k)4, 170.2(e)7 Traffic sign 140.7(a), 140.7(c), 140.8(b)6 Unfiltered neon 140.8(a), 170.2(d)7 Significant Contaminant 160.2(c)8 Single Family buildings 150.0, 150.1, 150.2, 110.10(a), 110.10(b)1A, 110.10(c), 110.6(a)6, 110.8(d)1, 150.0(k)3, 150.0(s), 150.1(a), 150.1(c)1, 150.1(c)11, 150.1(c)14, 150.2(a) Phase 120.6(a)3 Pole circuit breaker space 150.0(n), 160.4(a) Pole double throw 140.6(a)1, 170.2(e)2 Side opening 160.2(c)2 Zone air conditioner 160.3(d)1 Zone central forced air system 150.0(m)13, 160.3(b)G-L Zone damper 120.1(d), 160.2(c)5 Zone heat pump 120.2(b) Zone space conditioning system 120.4(g), 140.4(a) cabinet 140.4(c)1 Site-Recovered 140.4(d), 140.4(g) Site-Solar Energy 140.4(d), 140.4(g) Sizing(Equipment) 140.4(a), 150.0(h), 160.3(b)2, 170.

  • CALGreen § 3-4 Medium relevance — show source text

    302 Mixed Occupancy Buildings . . . . . . . . . . . . . . . . . . . . . . .3-4 303 Phased Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4 304 Voluntary Tiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4 305 CALGreen Tier 1 and CALGreen Tier 2 . . . . . . . . . . . . . .3-4

    306 Voluntary Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4

    CHAPTER 4 RESIDENTIAL MANDATORY MEASURES . . . . . . 4-3

    4.1 Planning and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3 4.2 Energy Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7 4.3 Water Efficiency and Conservation . . . . . . . . . . . . . . . . .4-9 4.4 Material Conservation and Resource Efficiency . . . . 4-11 4.5 Environmental Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

    CHAPTER 5 NONRESIDENTIAL MANDATORY MEASURES . . 5-3

    5.1 Planning and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3 5.2 Energy Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15 5.3 Water Efficiency and Conservation . . . . . . . . . . . . . . . 5-19 5.4 Material Conservation and Resource Efficiency . . . . 5-23 5.5 Environmental Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31

    CHAPTER 6 REFERENCED ORGANIZATIONS

    AND STANDARDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

    601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3

    CHAPTER 7 INSTALLER AND SPECIAL

    INSPECTOR QUALIFICATIONS . . . . . . . . . . . . . . . . . . . . . . 7-3 701 General (Reserved) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3 702 Qualifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3

Frequently asked questions

Do bathroom fans always need a humidity control?

Not if the fan is functioning as a component of a whole‑house ventilation system. Otherwise a humidity control adjustable between ≤ 50% and 80% RH is required. § 4.506.1.

What moisture reading prevents enclosure of framing?

If any framing member reads > 19% moisture content (measured 2–4 ft from the grade end), that member cannot be enclosed until dried or replaced. § 4.505.3.

Must HVAC designers literally use Manual J, D and S?

The code requires sizing and selection using those methods or equivalent design software or methods; document the calculations (Manual J for load, Manual D for ducts, Manual S for equipment). § 4.507.2.

Can an ENERGY STAR fan's integral light follow different rules?

Lighting integral to bathroom exhaust fans must comply with the California Energy Code (separate energy requirements), while the exhaust and humidity control requirements remain under § 4.506.1.

Is there a mandatory filter requirement in CALGreen?

For nonresidential mechanically ventilated buildings, CALGreen mandates MERV 13 for outside/return air filtration (§ 5.504.5). Construction‑period filter guidance (MERV 8) appears in Appendix A (voluntary/residential guidance).

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