CRC · California Residential Code

What glazing and exhaust requirements apply to bathrooms and similar rooms?

For homeowners: small bathrooms must either have 3 square feet of windows (with half that area able to open) or have artificial lighting and a mechanical exhaust fan. If the room has a tub or shower, a mechanical fan is required for humidity control — a window alone isn’t enough; exhaust must vent to the outdoors (see § R325.2 and § R325.2.1) .

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Bathrooms, water‑closet compartments and similar rooms must have an aggregate glazing area of not less than 3 square feet (0.3 m²), one‑half of which must be openable unless the artificial‑light plus local‑exhaust exception is used (§ R325.2) . If the glazed area is omitted under the exception, a local exhaust system is required at 50 cfm (25 L/s) intermittent or 20 cfm (10 L/s) continuous, and exhaust must discharge directly to the outdoors (§ R325.2) . In addition, any bathroom that contains a bathtub, shower or tub/shower combination must be mechanically ventilated for humidity control — window operation alone is not acceptable (§ R325.2.1) .

The single most important rule: provide either the required glazing (3 ft², half openable) or provide a compliant mechanical exhaust system sized and ducted to outdoors; bathrooms with bathing fixtures always need mechanical ventilation for humidity control (§ R325.2 and § R325.2.1) .

Requirements in detail

Glazing (natural light / natural ventilation)

  • Required aggregate glazing area: 3 square feet (0.3 m²). One‑half must be openable (i.e., 1.5 ft² openable) — § R325.2 .
  • The glazing requirement is specific to bathrooms, water‑closet compartments and similar rooms — § R325.2 .

Mechanical exhaust (when glazing is omitted or for humidity control)

  • Exception to glazing: glazed areas are not required where artificial light and a local exhaust system are provided — § R325.2 .
  • Minimum local exhaust rates required by the exception:
    • 50 cfm (25 L/s) — intermittent operation, or
    • 20 cfm (10 L/s) — continuous operation.
      These rates are stated in the exception to § R325.2 and reference the California Mechanical Code, Chapter 4 .
  • Exhaust air from the space shall be exhausted directly to the outdoors (no recirculation) — § R325.2 .
  • Independent requirement for bathrooms with bathing fixtures: each bathroom containing a bathtub, shower or tub/shower combination shall be mechanically ventilated for humidity control in accordance with the California Mechanical Code; window operation is not a permissible method for this humidity control — § R325.2.1 .

Decision‑relevant summary table

Decision factor Required value / threshold Code Reference
Aggregate glazing area for bathroom or similar room 3 ft² (0.3 m²) § R325.2
Openable portion of glazing ≥ one‑half (i.e., ≥1.5 ft²) § R325.2
Allowed alternative to glazing Artificial light + local exhaust § R325.2
Local exhaust — intermittent 50 cfm (25 L/s) § R325.2
Local exhaust — continuous 20 cfm (10 L/s) § R325.2
Exhaust termination Directly to outdoors (no recirculation) § R325.2
Bathrooms with tub/shower — humidity control Mechanically ventilated; window not acceptable § R325.2.1

Exceptions & special cases

  • The glazing minimum is waived only when both artificial lighting and a compliant local exhaust system are provided; you cannot remove glazing solely by providing ventilation or lighting alone — § R325.2 .
  • The stated exhaust rates in the exception are minimums; the California Mechanical Code may provide additional or alternative methods for calculating ventilation and capture efficiency (referenced by § R325.2 and by Chapter 4 of the Mechanical Code) .
  • Regardless of glazing or exhaust choice, bathrooms that contain bathing fixtures (bathtub, shower, tub/shower) require mechanical ventilation for humidity control; a window does not satisfy that humidity‑control requirement (§ R325.2.1) .
  • Exhaust air required by the exception must be ducted and terminated directly outdoors; make sure exhaust terminations comply with other CRC/CMC placement and screen requirements (see related provisions) — § R325.2 .

Common mistakes

  • Relying on an operable window alone to meet humidity‑control requirements for a bathroom with a tub or shower. The code explicitly disallows window operation for humidity control — § R325.2.1 .
  • Providing a recirculating/ductless fan and claiming compliance. The exception requires exhaust directly to the outdoors — § R325.2 .
  • Installing insufficient fan capacity (e.g., specifying a 30 cfm intermittent fan when 50 cfm intermittent is required, unless continuous 20 cfm operation is used) — check the intermittent vs continuous thresholds in § R325.2 .
  • Forgetting that the glazing requirement is an aggregate area — multiple small windows that together total less than 3 ft² do not comply; ensure the total glazed area meets or exceeds 3 ft² and that half of that area is openable — § R325.2 .
  • Omitting proper duct termination or routing (exhaust must discharge outdoors; location and screening requirements in other R325 sections and the CMC must be followed) — § R325.2 and related sections .

Worked example

Scenario: Detached dwelling bathroom with a bathtub, floor area 36 ft².

  1. Because the bathroom contains a bathtub, it must be mechanically ventilated for humidity control — § R325.2.1 . A window alone will not satisfy this requirement.
  2. Option A — Provide glazing: you could also provide natural light/ventilation. If you choose glazing instead of using the exception, the room must have 3 ft² total glazed area, 1.5 ft² of which must be openable — § R325.2 . But recall R325.2.1 still requires mechanical ventilation for humidity control because the room has a tub/shower.
    • Conclusion: even if you provide the 3 ft² glazing (with 1.5 ft² openable), because the room contains a tub/shower you still need mechanical ventilation for humidity control per § R325.2.1 .
  3. Option B — Use the exception (no glazing required): provide artificial lighting plus a local exhaust fan sized 50 cfm intermittent or 20 cfm continuous, ducted directly to outdoors — § R325.2 . This option also satisfies the mechanical ventilation requirement in § R325.2.1 for humidity control provided the fan meets the Mechanical Code/CalGreen requirements referenced by the CRC (see § R325.2.1) .

Practical installer decision: for a bathroom with bathtub, the straightforward compliance path is to install a mechanical exhaust fan sized at 50 cfm (intermittent) or 20 cfm (continuous), duct it to the exterior, and provide artificial lighting — that meets both § R325.2 and § R325.2.1 .

Related provisions

  • § R325.3 — Ventilation air rates are to comply with the California Mechanical Code (see CRC cross‑reference) .
  • § R325.4 / R325.4.1 / R325.4.2 — Location rules for intake and exhaust openings, and separation from contaminants; exhaust shall not be directed onto walkways — these affect where bathroom exhaust can terminate .
  • California Mechanical Code, Chapter 4 — referenced by CRC for ventilation and airflow rate methodology and definitions (bathroom exhaust rates and mechanical ventilation requirements) .
  • California Energy / CALGreen (local mechanical exhaust requirements and demand/continuous control options) — referenced by CRC and the Building/Energy chapters for system control and performance in some occupancies .

Code references

Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:

  • CRC § 1.9 High relevance — show source text

    1. Natural ventilation shall not be required in kitchens where a local exhaust system is installed in accordance with the California Mechanical Code .

    2. Required ventilation openings shall be permitted to open into a thermally isolated sunroom or roofed porch, deck, or patio where not less than 40 percent of the roofed area perimeter is open to the outdoor air.

    3. Required ventilation openings shall be permitted to open into a thermally isolated sunroom provided there is an openable area between the adjoining room and the sunroom of not less than one-tenth of the floor area of the interior room and not less than 20 square feet (1.9 m [2] ). The minimum openable area of the sunroom to outdoor air shall be based on the total floor area of the adjoining room and the sunroom. 5. The windows, doors, louvers and other approved closeable openings not required by Section R319 may open into a passive solar energy collector for ventilation required by this section. The area of ventilation openings to the outside of the passive solar energy collector shall be increased to compensate for the openings required by the interior space.

    R325.1.3 Adjoining rooms. For the purpose of determining light and ventilation requirements, rooms shall be considered to be a portion of an adjoining room where not less than one-half of the area of the common wall is open and unobstructed and provides an opening of not less than one-tenth of the floor area of the interior room and not less than 25 square feet (2.3 m [2] ).

    R325.2 Bathrooms. Bathrooms, water closet compartments and other similar rooms shall be provided with aggregate glazing area in windows of not less than 3 square feet (0.3 m [2] ), one-half of which shall be openable.

    Exception: The glazed areas shall not be required where artificial light and a local exhaust system are provided. The minimum local exhaust rates shall be 50 cubic feet per minute (25 L/s) for intermittent ventilation or 20 cubic feet per minute (10 L/s) for contin- uous ventilation in accordance with the California Mechanical Code, Chapter 4 . Exhaust air from the space shall be exhausted directly to the outdoors.

    R325.2.1 Bathroom exhaust fans. Each bathroom containing a bathtub, shower or tub/shower combination shall be mechanically ventilated for purposes of humidity control in accordance with the California Mechanical Code, Chapter 4; and the California Green Building Standards Code, Chapter 4, Division 4.5.

    Note: Window operation is not a permissible method of providing bathroom exhaust for humidity control.

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    BUILDING PLANNING

    R325.3 Ventilation. Ventilation air rates shall be in compliance with the California Mechanical Code.

    R325.4 Opening location. Outdoor intake and exhaust openings shall be located in accordance with Sections R325.4.1 and R325.4.2.

    R325.4.1 Intake openings. Mechanical and gravity outdoor air intake openings shall be located not less than 10 feet (3048 mm) from any hazardous or noxious contaminant, such as vents, chimneys, plumbing vents, streets, alleys, parking lots and loading docks.

    For the purpose of this section, the exhaust from dwelling unit toilet rooms, bathrooms and kitchens shall not be considered as hazardous or noxious.

  • CRC § 2.1 High relevance — show source text

    Exception: The glazed areas shall not be required where artificial light and a local exhaust system are provided. The minimum local exhaust rates shall be 50 cubic feet per minute (25 L/s) for intermittent ventilation or 20 cubic feet per minute (10 L/s) for contin- uous ventilation in accordance with the California Mechanical Code, Chapter 4 . Exhaust air from the space shall be exhausted directly to the outdoors.

    R325.2.1 Bathroom exhaust fans. Each bathroom containing a bathtub, shower or tub/shower combination shall be mechanically ventilated for purposes of humidity control in accordance with the California Mechanical Code, Chapter 4; and the California Green Building Standards Code, Chapter 4, Division 4.5.

    Note: Window operation is not a permissible method of providing bathroom exhaust for humidity control.

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    R325.3 Ventilation. Ventilation air rates shall be in compliance with the California Mechanical Code.

    R325.4 Opening location. Outdoor intake and exhaust openings shall be located in accordance with Sections R325.4.1 and R325.4.2.

    R325.4.1 Intake openings. Mechanical and gravity outdoor air intake openings shall be located not less than 10 feet (3048 mm) from any hazardous or noxious contaminant, such as vents, chimneys, plumbing vents, streets, alleys, parking lots and loading docks.

    For the purpose of this section, the exhaust from dwelling unit toilet rooms, bathrooms and kitchens shall not be considered as hazardous or noxious.

    Exceptions:

    1. The 10-foot (3048 mm) separation is not required where the intake opening is located 3 feet (914 mm) or greater below the contaminant source.

    2. Vents and chimneys serving fuel-burning appliances shall be terminated in accordance with the applicable provisions of the California Mechanical Code.

    3. Clothes dryer exhaust ducts shall be terminated in accordance with the California Mechanical Code.

    R325.4.2 Exhaust openings. Exhaust air shall not be directed onto walkways.

    R325.5 Outside opening protection. Air exhaust and intake openings that terminate outdoors shall be protected with corrosionresistant screens, louvers or grilles having an opening size of not less than [1] / 4 inch (6 mm) and a maximum opening size of [1] / 2 inch (13 mm), in any dimension. Openings shall be protected against local weather conditions. Outdoor air exhaust and intake openings shall meet the provisions for exterior wall opening protectives in accordance with this code.

    R325.6 Interior stairway illumination. Interior stairways shall be provided with an artificial light source to illuminate the landings and treads. The light source shall be capable of illuminating treads and landings to levels of not less than 1 footcandle (11 lux) as measured at the center of treads and landings. There shall be a wall switch at each floor level to control the light source where the stairway has six or more risers.

    Exception: A switch is not required where remote, central or automatic control of lighting is provided.

  • CRC § 0.50 High relevance — show source text

    50|3| |Arenas2|–|0.50|1| |Art classrooms|–|0.70|2| |Auto repair rooms1|–|1.50|2| |Barber shops|–|0.50|2| |Bathroom10, 11|20/50|–|2| |Beauty and nail salons|–|0.60|2| |Cells with toilet|–|1.00|2| |Copy, printing rooms|–|0.50|2| |Darkrooms|–|1.00|2| |Educational science laboratories|–|1.00|2| |Janitor closets, trash rooms, recycling|–|1.00|3| |Kitchenettes|–|0.30|2| |Kitchens – commercial|–|0.70|2| |Locker rooms for athletic, industrial and health care facilities|–|0.50|2| |All other locker rooms|–|0.25|2| |Shower rooms7, 9|20/50|–|2| |Paint spray booths6|–|–|4| |Parking garages3|–|0.75|2| |Pet shops (animal areas)|–|0.90|2| |Refrigerating machinery rooms6|–|–|3| |Residential kitchens7|50/100|–|2| |Soiled laundry storage rooms6|–|1.00|3| |Storage rooms, chemical6|–|1.50|4| |Toilets – private5, 8|25/50|–|2| |Toilets – public4, 8|50/70|–|2| |Woodwork shop/classrooms|–|0.50|2|

    For SI units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per minute per square foot = 5.08 [(L/s)/m [2] ]

    Notes: 1 Stands where engines are run shall have exhaust systems that directly connect to the engine exhaust and prevent escape of fumes. 2 Where combustion equipment is intended to be used on the playing surface, additional dilution ventilation, source control, or both shall be provided. 3 Exhaust shall not be required where two or more sides compose walls that are at least 50 percent open to the outside. 4 Rate is per water closet, urinal, or both. Provide the higher rate where periods of heavy use are expected to occur. The lower rate shall be permitted to be used otherwise. 5 Rate is for a toilet room intended to be occupied by one person at a time. For continuous system operation during hours of use, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used. 6 See other applicable standards for exhaust rate. 7 For continuous system operation, the lower rates shall be permitted to be used. Otherwise the higher rate shall be used. 8 Exhaust air that has been cleaned to meet Class 1 criteria from Section 403.9 shall be permitted to be recirculated. 9 Rate is per showerhead. 10 [HCD 1 & HCD 2] A bathroom is any room containing a bathtub, a shower, a spa, or a similar source of moisture. 11 [HCD 1 & HCD 2] ANSI/ASHRAE 62.2: Tables 5.1 and 5.2.

  • CRC § 150.0 High relevance — show source text

    D. Air filtration. Air filtration shall conform to the specifications in Section 150.0(m)12. Compliance with ASHRAE 62.2 Sections 6.7 (Minimum Filtration) and 6.7.1 (Filter Pressure Drop) shall not be required.

    E. Reserved.

    F. Reserved.

    G. Local mechanical exhaust. A local mechanical exhaust system shall be installed in each kitchen and bathroom. Systems shall be rated for airflow in accordance with ASHRAE 62.2 Section 7.1. i. Nonenclosed kitchens shall have a demand-controlled mechanical exhaust system meeting the requirements of Section 150.0(o)1Giii. ii. Enclosed kitchens and all bathrooms shall have either one of the following alternatives a or b: a. A demand-controlled mechanical exhaust system meeting the requirements of Section 150.0(o)1Giii. b. A continuous mechanical exhaust system meeting the requirements of Section 150.0(o)1Giv. iii. Demand-controlled mechanical exhaust. A local mechanical exhaust system shall be designed to be operated as needed.

    a. Control and operation. Demand-controlled mechanical exhaust systems shall be provided with at least one of the following controls:

    1. A readily accessible occupant-controlled ON-OFF control.
    2. An automatic control that does not impede occupant ON control. b. Ventilation rate and capture efficiency. The system shall meet or exceed either the minimum airflow in accordance with Table 150.0-E or the minimum capture efficiency in accordance with Table 150.0-E, and Table 150.0-G. Capture efficiency ratings shall be determined in accordance with ASTM E3087 and listed in a product directory approved by the Energy Commission.
    TABLE 150.0-E—DEMAND-CONTROLLED LOCAL VENTILATION EXHAUST AIRFLOW RATES AND CAPTURE EFFICIENCY Col2
    APPLICATION COMPLIANCE CRITERIA
    Enclosed Kitchen or Nonenclosed Kitchen Vented range hood, including appliance-range hood combinations, shall meet either the
    capture efficiency (CE) or the airflow rate specified in Table 150.0-G as applicable.
    Enclosed Kitchen or Nonenclosed Kitchen Other kitchen exhaust fans, including downdraft: 300 cfm (150 L/s)
    Bathroom 50 cfm (25 L/s)

    iv. Continuous mechanical exhaust. A mechanical exhaust system shall be installed to operate continuously. The system may be part of a balanced mechanical ventilation system. a. Control and operation . A manual ON-OFF control shall be provided for each continuous mechanical exhaust system. The system shall be designed to operate during all occupiable hours. The ON-OFF control shall be accessible to the dwelling unit occupant.

    b. Ventilation rate. The minimum delivered ventilation shall be at least the amount indicated in Table 150.0-F during each hour of operation.

    TABLE 150.0-F—CONTINUOUS LOCAL VENTILATION EXHAUST AIRFLOW RATES Col2
    APPLICATION AIRFLOW
    Enclosed kitchen 5 ACH, based on kitchen volume
    Bathroom 20 cfm (10 L/s)
  • CRC § 8.4 High relevance — show source text

    Defined R202

    Inlet To masonry chimneys R1003.16 Inspection On-site 1.8.4, R109.1 Insulation

    Above-deck R906 Flame spread R302.10 Foam plastic R303 Interior

    Lath R702.2.3

    Other finishes R702.5

    Plaster R702.2 Wall covering Chapter 7 Intermodal Shipping Container R301.1.4

    Joist

    Bearing R502.6, R606.6.3.1

    Kitchen Height and area R312, R313 Sinks R326

    Ventilation R325.1.2

    Labeling Garage doors R609.4.1 Ladders

    Ships ladders R318.7.13 Sleeping lofts R315.5.3 Landings (see also Stairways, Ramps and Doors) R318.3, R318.3.1, R318.3.2, R318.7.6, R318.8.2, R321, R324.4.7, R325.6, R325.7 Lateral Support R502.7, R606.6.4, R607.5.2 Lath

    Exterior R703.7.1

    Interior R702.2.3

    Lavatories R326.1

    Clearances R327 Liability R104.8 Light R325 Lighting Adjoining rooms R325.1.3 Bathrooms R325.2

    Exterior stairs R325.7

    Habitable rooms R325

    Interior stairs R325.6 Limited-Density Owner-Built Rural Dwellings Alternative provisions R301.1.1.1 Definition R202 Lining Flue R1003.11, R1003.12 Lintel R606.10, R608.8, R703.8.3, R1001.7 Liquid Fuel R202 Live Loads (see Loads)

    Live/work Unit R101.2 Accessibility R322.2 Loads Chimneys R1003.8 Components and Cladding (see Wind Loads) Figure R301.2.1, Table 301.2.1(1), Table 301.2.1(2) Dead load R301.4 Flood (see Flood-Resistant Construction) R301.2.4 Live load R301.5, R301.7 Roof R301.6 Seismic risk map (see Seismic Loads) Figure R301.2.2.1(1), Figure R301.2.2.1(2), Figure R301.2.2.1(3), Figure R301.2.2.1(4), Figure R301.2.2.1(5), Figure R301.2.2.1(6), Figure R301.2.2.1(7) Snow load map (see Snow Loads) Figure 301.2(3) Wind speed map (see Wind Loads) Figure R301.2(2) Lodging House R101.2, R322.1 Lumber

    Grade R502.1.1, R602.1.1, R802.1.1

  • CRC § 4-2 High relevance — show source text

    _D_g
    (inches)    |** NUMBER OF BARS AND**
    BAR SIZE IN TOP AND
    BOTTOM OF LINTEL|     STEEL YIELD**
    STRENGTHh, ****fy
    (psi)| Maximum ground snow load
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)|** Maximum ground snow load**
    (psf)| |** LINTEL**
    DEPTH,****_D_g
    (inches)    |** NUMBER OF BARS AND**
    BAR SIZE IN TOP AND
    BOTTOM OF LINTEL|** STEEL YIELD**
    STRENGTHh, ****fy
    (psi)| —    |** 30**|** 70**|** 30**|** 70**|** 30**|** 70**|** 30**|** 70**| |** LINTEL**
    DEPTH,****_D_g
    (inches)    |** NUMBER OF BARS AND**
    BAR SIZE IN TOP AND
    BOTTOM OF LINTEL|** STEEL YIELD**
    STRENGTHh, ****fy
    (psi)| Maximum clear span of lintel
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)|** Maximum clear span of lintel**
    (feet-inches)| |8|Span without stirrupsi, j|Span without stirrupsi, j|4-2|4-8|3-1|3-3|2-10|2-6|2-3|2-0|2-0| |8|1-#4|40,000|5-1|5-5|4-2|4-3|3-10|3-6|3-3|2-8|2-7| |8|1-#4|60,000|6-2|6-7|5-0|5-2|4-8|4-2|3-11|3-3|3-2| |8|1-#5|40,000|6-3|6-8|5-1|5-3|4-9|4-3|4-0|3-3|3-2| |8|1-#5|60,

  • CRC § 2.5 High relevance — show source text

    Parapet construction R302.2.5 Scope R101.2 Separation R302.2 Structural independence R302.2.6 Trusses

    Steel R505.1.3, R804.3.6 Wood R502.12, R802.10 Tubular Daylighting Device (TDD) (see Skylights) Two-Family Dwellings R302.3

    Under Floor

    Space R408

    Vapor Retarders R702.7 Capillary break R506.2.3.1 Under floor R408.8 Vehicular Gates Appendix BH Veneer

    Masonry R703.7 Ventilation Adjoining rooms R325.1.3 Bathroom and kitchen R325.2

    Habitable rooms R325.1

    Roof R806

    Under floor R408.1 Venting (Mechanical) Chimney and vent connectors R1006 Fireplace R1006 General R325.3

    Violations R113 Visible Transmittance (VT)

    Wall Furnace (see Appliance) Wallboard (see Gypsum) Walls

    Bathtub compartments R327.2 Bracing, steel R603.9 Bracing, wood R602.10 Construction Chapter 6 Covering Chapter 7 Crawl space R202 Cripple R602.9

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    INDEX

    Deflection R301.7

    Exterior, defined R202 Exterior covering R703 Finishes R327.2, R702 Fireplace R1001.5 Foundation R404 Insulating concrete form R608.3, R608.4, R608.5.3 Steel framing R603 Structural insulated panels (SIP) R610 Thickness, masonry chimneys R1003.10 Wood framing R602 Waste

    Construction waste R334

    Water Closet R326.1, R327 Clearances for R327.1 Waterproofing And dampproofing R406 Wells (see Individual Water Supply) Whirlpool Bathtubs R324.3.1, P2720 Wind

    Design criteria R301.2, R301.2.1 Speed maps Figure R301.2(2) Window R609 Emergency Escape and Rescue Openings R319, R321.2.2 Fall protection R321.2 Glazing R324 Light and ventilation R325 Opening limiting devices R321.2.2 Wood

    Floor construction R502

    Foundation walls R404.2 Protection against decay R304 Roof-ceiling construction R802 Shakes R905.8 Shingles R905.7 Trusses R502.12, R802.10 Walls R602

    Yard R318.1, R319.1, R319.2.4, R325.1.1

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    HISTORY NOTE APPENDIX

  • CRC § 160.2 High relevance — show source text

    a. Designers shall specify a design ventilation airflow rate for each dwelling unit that is equal to or greater than the rate specified by Equation 160.2-B. b. The design ventilation airflow rate for each dwelling unit shall be stated on the building design plans approved by the enforcement agency. c. Airflow in each dwelling unit shall be no more than 20 percent greater than the specified design ventilation airflow rate. Ventilation systems shall utilize mechanical or software airflow control means to ensure each of the dwelling-unit airflows can be maintained at the design ventilation airflow within this tolerance at all times. System airflow control-means may include but are not limited to constant air regulation devices, orifice plates and variable speed central fans. vi. Local mechanical exhaust. A local mechanical exhaust system shall be installed in each kitchen and bathroom. Systems shall be rated for airflow in accordance with ASHRAE 62.2 Section 7.1. a. Nonenclosed kitchens shall have a demand-controlled mechanical exhaust system meeting the requirements of Section 160.2(b)2Avic. b. Enclosed kitchens and all bathrooms shall have either one of the following options 1 or 2:

    1. A demand-controlled mechanical exhaust system meeting the requirements of Section 160.2(b)2Avic; or

    2. A continuous mechanical exhaust system meeting the requirements of Section 160.2(b)2Avid. c. Demand-controlled mechanical exhaust. A local mechanical exhaust system shall be designed to be operated as needed.

    3. Control and operation. Demand-controlled mechanical exhaust systems shall be provided with at least one of the following controls: A. A readily accessible occupant-controlled ON-OFF control. B. An automatic control that does not impede occupant ON control.

    4. Ventilation rate and capture efficiency. The system shall meet or exceed either the minimum airflow in accordance with Table 160.2-E or the minimum capture efficiency in accordance with Table 160.2-E, and Table 160.2-G. Capture efficiency ratings shall be determined in accordance with ASTM E3087, and listed in a product directory approved by the Energy Commission. d. Continuous mechanical exhaust. A mechanical exhaust system shall be installed to operate continuously. The system may be part of a balanced mechanical ventilation system.

    5. Control and operation . A manual ON-OFF control shall be provided for each continuous mechanical exhaust system. The system shall be designed to operate during all occupiable hours. For multifamily dwelling units, the manual ON-OFF control may be accessible to the dwelling unit occupant; however, the manual ON-OFF control shall not be required to be accessible to the dwelling unit occupant.

    6. Ventilation rate. The minimum delivered ventilation shall be at least the amount indicated in Table 160.2-F during each hour of operation. e. Airflow measurement of local mechanical exhaust by the system installer. The airflow required by Section 160.2(b)2Avi is the quantity of indoor air exhausted by the ventilation system as installed in the dwelling unit. When a vented range hood utilizes a capture efficiency rating to demonstrate compliance with Section 160.2(b)2Avic2, the airflow listed in the approved directory corresponding to the compliant capture efficiency rating point shall be met by the installed system. The as-installed airflow shall be verified by the system installer to ensure compliance by use of either Subsection 1 or 2 below:

  • CRC § 2.5. Medium relevance — show source text

    Exception: Bracing above the roofline shall not be required where the maximum height of unbraced unreinforced masonry does not exceed a height-to-width ratio of 2.5. Height shall be measured from the top of the parapet down to the highest existing brace or anchor point attached to the structure.

    BO105.5 Electrical equipment and wiring. Electrical equipment and wiring shall comply with this section.

    BO105.5.1 Materials and methods. Newly installed electrical equipment and wiring relating to work done in any work area, including in newly installed partitions and ceilings, shall comply with the materials and methods requirements of Chapters 34 through 43.

    BO105.5.2 Electrical service. Service to the dwelling unit shall be not less than 100 ampere, three-wire capacity, and service equipment shall be dead front having no live parts exposed that could allow accidental contact. Type “S” fuses shall be installed where fused equipment is used.

    Exception: Existing service of 60 ampere, three-wire capacity, and feeders of 30 ampere or larger two- or three-wire capacity shall be accepted if adequate for the electrical load being served.

    BO105.5.3 Additional electrical requirements. Where the work area includes any of the following areas within a dwelling unit, the requirements of Sections BO105.5.3.1 through BO105.5.3.5 shall apply.

    BO105.5.3.1 Enclosed areas. Enclosed areas other than closets, kitchens, basements, garages, hallways, laundry areas and bathrooms shall have not fewer than two duplex receptacle outlets, or one duplex receptacle outlet and one ceiling- or walltype lighting outlet.

    BO105.5.3.2 Kitchen and laundry areas. Kitchen areas shall have not fewer than two duplex receptacle outlets. Laundry areas shall have not fewer than one duplex receptacle outlet located near the laundry equipment and installed on an independent branch circuit.

    BO105.5.3.3 Ground-fault circuit interruption. Ground-fault circuit interruption shall be provided on newly installed receptacle outlets if required by Chapters 34 through 43.

    BO105.5.3.4 Lighting outlets. Not less than one lighting outlet controlled by a listed wall-mounted device shall be provided in every bathroom, hallway, stairway, attached garage and detached garage with electric power to illuminate outdoor entrances and exits, and in utility rooms and basements where these spaces are used for storage or contain equipment requiring service. The wall-mounted control device shall be located near an entrance to the room.

    BO105.5.3.5 Clearance. Clearance for electrical service equipment shall be provided in accordance with Chapters 34 through 43.

    BO105.6 Ventilation. Reconfigured spaces intended for occupancy and spaces converted to habitable or occupiable space in any work area shall be provided with ventilation in accordance with Section R325.

    BO105.7 Ceiling height. Where a habitable attic or habitable space is created in an existing building, ceiling heights shall be not less than 6 feet 8 inches (2032 mm). Bathrooms, toilet rooms and laundry rooms shall have a ceiling height of not less than 6 feet 4 inches (1930 mm).

  • CRC § 1.0 Medium relevance — show source text

    0|–| |Dental Unit, cuspidor|1⁄2|–|1.0|–| |Dishwasher, domestic|1⁄2|1.5|1.5|–| |Drinking Fountain or Water Cooler|1⁄2|0.5|0.5|0.75| |Hose Bibb|1⁄2|2.5|2.5|–| |Hose Bibb, each additional7|1⁄2|1.0|1.0|–| |Lavatory|1⁄2|1.0|1.0|1.0| |Lawn Sprinkler, each head5|–|1.0|1.0|–| |Mobile Home, each (minimum)|–|12.0|–|–| |Sinks|–|–|–|–| |Bar|1⁄2|1.0|2.0|–| |Clinical Faucet|1⁄2|–|3.0|–| |Clinical Flushometer Valve with or without faucet|1|–|8.0|–| |Kitchen, domestic with or without dishwasher|1⁄2|1.5|1.5|–| |Laundry|1⁄2|1.5|1.5|–| |Service or Mop Basin|1⁄2|1.5|3.0|–| |Washup, each set of faucets|1⁄2|–|2.0|–| |Shower per head|1⁄2|2.0|2.0|–| |Urinal, 1.0 GPF Flushometer Valve|3⁄4|3.0|4.0|5.0| |Urinal, greater than 1.0 GPF Flushometer Valve|3⁄4|4.0|5.0|6.0| |Urinal, flush tank|1⁄2|2.0|2.0|3.0| |Wash Fountain, circular spray|3⁄4|–|4.0|–| |Water Closet, 1.6 GPF Gravity Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Valve|1|5.0|5.0|8.0| |Water Closet, greater than 1.6 GPF Gravity Tank|1⁄2|3.0|5.5|7.0| |Water Closet, greater than 1.6 GPF Flushometer Valve|1|7.0|8.0|10.0|

    For SI units: 1 inch = 25 mm

    Notes: 1 Size of the cold branch pipe, or both the hot and cold branch pipes. 2 Appliances, appurtenances, or fixtures not included in this table shall be permitted to be sized by reference to fixtures having a similar flow rate and frequency of use. 3 The listed fixture unit values represent their total load on the cold water building supply. The separate cold water and hot water fixture unit value for fixtures having both cold and hot water connections shall be permitted to be three-quarters of the listed total value of the fixture. 4 The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size.

  • CRC § 1202.5.1 Medium relevance — show source text

    agency.

    [HCD 1] The windows, doors, louvers or other approved closeable openings not required by Section 1030 may open into a passive solar energy collector for ventilation required by this section. The area of ventilation openings to the outside of the passive solar energy collec- tor shall be increased to compensate for the openings required by the interior space.

    1202.5.1 Ventilation area required. The openable area of the openings to the outdoors shall be not less than 4 percent of the floor area being ventilated.

    1202.5.1.1 Adjoining spaces. Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 25 square feet (2.3 m [2] ). The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.

    Exception: Exterior openings required for ventilation shall be allowed to open into a sunroom with thermal isolation or a patio cover provided that the openable area between the sunroom addition or patio cover and the interior room shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 20 square feet (1.86 m [2] ). The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.

    1202.5.1.2 Openings below grade. Where openings below grade provide required natural ventilation, the outside horizontal clear space measured perpendicular to the opening shall be one and one-half times the depth of the opening. The depth of the opening shall be measured from the average adjoining ground level to the bottom of the opening.

    1202.5.2 Contaminants exhausted. Contaminant sources in naturally ventilated spaces shall be removed in accordance with the California Mechanical Code and the California Fire Code .

    1202.5.2.1 Bathrooms. Rooms containing bathtubs, showers, spas and similar bathing fixtures shall be mechanically ventilated in accordance with the California Mechanical Code .

    The minimum exhaust rate shall not be less than that established by Table 403.7 “Minimum Exhaust Rates.” See California Mechanical Code, Chapter 5, for additional provisions related to environmental air ducts.

    [HCD 1] In addition to the requirements in this section and in the California Mechanical Code, bathrooms in Group R occupancies shall be mechanically ventilated in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.5.

    1202.5.3 Openings on yards or courts. Where natural ventilation is to be provided by openings onto yards or courts, such yards or courts shall comply with Section 1205.

    1202.6 Other ventilation and exhaust systems. Ventilation and exhaust systems for occupancies and operations involving flammable or combustible hazards or other contaminant sources as covered in the California Mechanical Code or the California Fire Code shall be provided as required by both codes.

    SECTION 1203—TEMPERATURE CONTROL

    1203.1 Equipment and systems. Interior spaces intended for human occupancy shall be provided with active or passive space heating systems capable of maintaining an indoor temperature of not less than 68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day.

  • CRC § 1202.5.2 Medium relevance — show source text

    1202.5.2 Contaminants exhausted. Contaminant sources in naturally ventilated spaces shall be removed in accordance with the California Mechanical Code and the California Fire Code .

    1202.5.2.1 Bathrooms. Rooms containing bathtubs, showers, spas and similar bathing fixtures shall be mechanically ventilated in accordance with the California Mechanical Code .

    The minimum exhaust rate shall not be less than that established by Table 403.7 “Minimum Exhaust Rates.” See California Mechanical Code, Chapter 5, for additional provisions related to environmental air ducts.

    [HCD 1] In addition to the requirements in this section and in the California Mechanical Code, bathrooms in Group R occupancies shall be mechanically ventilated in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.5.

    1202.5.3 Openings on yards or courts. Where natural ventilation is to be provided by openings onto yards or courts, such yards or courts shall comply with Section 1205.

    1202.6 Other ventilation and exhaust systems. Ventilation and exhaust systems for occupancies and operations involving flammable or combustible hazards or other contaminant sources as covered in the California Mechanical Code or the California Fire Code shall be provided as required by both codes.

    SECTION 1203—TEMPERATURE CONTROL

    1203.1 Equipment and systems. Interior spaces intended for human occupancy shall be provided with active or passive space heating systems capable of maintaining an indoor temperature of not less than 68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day.

    Exceptions: 1. Space heating systems are not required for: 1.1. Interior spaces where the primary purpose of the space is not associated with human comfort.

    1.2. Group F, H, S or U occupancies. 2. [HCD 1] For limited-density owner-built rural dwellings, a heating facility or appliance shall be installed in each dwelling subject to the provisions of Subchapter 1, Chapter 1, Title 25, California Code of Regulations, commencing with Section 74; however, there shall be no specified requirement for heating capacity or temperature maintenance. The use of solid-fuel or solar-heating devices shall be deemed as complying with the requirements of this section. If nonrenewable fuel is used in these dwellings, rooms so heated shall meet current installation standards. 3. [OSHPD 1, 1R, 2, 3, 4 & 5] Space heating systems shall comply with the requirements of the California Mechanical Code. 4. [HCD 1] When a passive solar energy collector is designed as a conditioned area it shall comply with the California Energy Code. Nonconditioned passive solar energy collectors are exempt from compliance with the California Energy Code.

    12-6 2025 CALIFORNIA BUILDING CODE

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

    INTERIOR ENVIRONMENT

    SECTION 1204—LIGHTING

    1204.1 General. Every space intended for human occupancy shall be provided with natural light by means of exterior glazed openings in accordance with Section 1204.2 or shall be provided with artificial light in accordance with Section 1204.3. Exterior glazed openings shall open directly onto a public way or onto a yard or court in accordance with Section 1205.

Frequently asked questions

Does providing a window satisfy the code so I don’t need a fan?

A window can satisfy the glazing (light/ventilation) requirement, but it does not satisfy the humidity‑control requirement for bathrooms that contain a bathtub, shower or tub/shower combination — § R325.2.1 . Those bathrooms must have mechanical ventilation; window operation is not acceptable for humidity control.

Can I use a ductless (recirculating) fan to meet the exhaust requirement?

No. The exception in § R325.2 requires that exhaust air be exhausted directly to the outdoors; recirculating (ductless) fans do not comply .

If I choose the exhaust option, what fan sizes are acceptable?

Per § R325.2 the minimums are 50 cfm intermittent or 20 cfm continuous. Confirm sizing and any additional requirements by the California Mechanical Code referenced in the CRC .

Do the exhaust terminations have placement rules?

Yes — exhaust terminations must discharge outdoors and must comply with the CRC and CMC location and screening requirements (for example, exhaust should not be directed onto walkways) — see § R325.2 and § R325.4.2 file.

If a bathroom has only a water closet (toilet) but no shower or tub, do I still need a mechanical fan?

The glazing requirement still applies (3 ft², half openable) and the exception permits artificial light + local exhaust at the stated rates; the separate humidity‑control mandate in § R325.2.1 applies specifically to rooms containing bathtubs, showers or tub/shower combinations .

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