CRC · California Residential Code

Residential ventilation — ASHRAE 62.2, and CRC/CMC applicability

Q: How is the required whole‑house ventilation flow (Qtot) computed?

Qtot is computed by the CMC Appendix E formula: Qtot = 0.03 · Afloor + 7.5 · (Nbr + 1) (CFM). See § E 605.1.3.1 .

Q: Can I use windows instead of mechanical ventilation?

Not generally in California. The Energy Code requires mechanical ventilation per ASHRAE 62.2 with limited AHJ exceptions; check § 150.0(o) and § E 605.1.3 for the narrow circumstances where window operation may be allowed.

Q: Can infiltration reduce the mechanical ventilation requirement?

Yes — calculate the Effective Annual Average Infiltration Rate (Qinf) from a blower‑door Q50 using § E 605.1.3.2 and subtract it from Qtot to size mechanical ventilation, subject to ASHRAE 62.2 weather/shielding factors.

Q: What must a CFI (central fan integrated) ventilation system include to comply in California?

CFI systems must have motorized outdoor‑air damper(s) that close when ventilation is not required, controls to track run time, and must not use continuous AHU fan operation as the sole method for whole‑house ventilation — per the Energy Code amendments in § 150.0(o) .

Q: Where do I find the required sound and measurement procedures for the installed ventilation?

The Energy Code (Section 160.2) requires airflow measurement at the fan inlet/outlet using approved methods and sound rating per ASHRAE 62.2 procedures; see § 160.2 for those test/label rules.

Homeowners: California law requires homes to have mechanical ventilation sized by ASHRAE 62.2 methods as modified by California. The code gives a simple equation (Qtot = 0.03·floor area + 7.5·(bedrooms+1)) and allows a measured infiltration credit; systems must be controlled, labeled, and verified as installed.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

California requires that all dwelling units meet the residential ventilation provisions of ASHRAE 62.2 as adopted and amended by the California codes; the California Energy Code explicitly directs compliance with ASHRAE 62.2 in § 150.0(o). For mechanical-ventilation calculations the California Mechanical Code (CMC) provides dwelling‑unit procedures in § 405.0 and the Appendix/energy provisions (CMC Appendix E) give the low‑rise dwelling calculation and testing method in § E 605.1.3. For low‑rise HVAC equipment sizing and system requirements see § E 502.2.

The single most important rule: dwelling units in California must provide whole‑dwelling mechanical ventilation sized and operated using ASHRAE 62.2 methods as amended by the California Energy Code — you must follow the California amendments and the CMC calculation procedures.

Requirements in detail

Governing references (short)

ASHRAE 62.2 (adopted and amended by California) — California Energy Code direction: § 150.0(o).
CMC Chapter 4 / Dwelling unit ventilation: CMC directs that dwelling‑unit ventilation rates be provided in accordance with § 405.0 or ASHRAE 62.2.
CMC Appendix E — Dwelling unit calculation: the Appendix gives the explicit whole‑dwelling calculation and infiltration credit in § E 605.1.3 and subparts.
Low‑rise HVAC equipment & system rules: § E 502.2 (equipment scope and related requirements).

Key defined terms (first mention bolded)

Whole‑dwelling ventilation — the ventilation needed to provide acceptable IAQ for the entire dwelling unit (mechanical supply, exhaust, or balanced).
Qtot — total required ventilation rate (CFM) for the dwelling (the CMC/Appendix E symbol).
Afloor and Nbr — floor area (ft2) and number of bedrooms (used in the Qtot equation).

Calculation (decision table)

Decision dimension	Value / threshold	How it affects design	Code reference
Whole‑dwelling required flow (Qtot)	Qtot = 0.03 · Afloor + 7.5 · (Nbr + 1) (CFM)	Use to size continuous or equivalent intermittent system capacity.	§ E 605.1.3.1
Infiltration credit (Qinf)	Qinf = 0.052 × Q50 × wsf × (H/Hr)^z (CFM)	Can reduce required mechanical ventilation; Q50 from blower door, wsf per ASHRAE 62.2.	§ E 605.1.3.2
Bathroom local exhaust	50 cfm intermittent or 20 cfm continuous	Minimum local exhaust for rooms with bathtub/shower; fans must vent outdoors.	§ E 605.2
Whole‑house sound rating & measurement	Systems must be rated per ASHRAE 62.2 sound rules; airflow measured at fan inlet/outlet by flow hood or approved method	Ensures installed flow = design flow.	§ 160.2 (Energy Code details)
Central‑fan‑integrated (CFI) controls	Motorized outdoor‑air damper(s) required; continuous AHU fan as the sole ventilation method is not permitted; variable control & run‑time tracking required	CFI systems must actively control outdoor air and damper positions per CA amendments.	§ 150.0(o) amendments (Energy Code)
Equipment scope (low‑rise)	Single‑phase equipment, A/C <65,000 Btu/h, furnaces <225,000 Btu/h, boilers <300,000 Btu/h	E 502.2 limits which equipment the low‑rise rules apply to.	§ E 502.2

Operational & installation controls

Labeling: whole‑dwelling ventilation ON‑OFF control must carry a label instructing occupants to leave the switch ON except during poor outdoor air events (Energy Code amendment). § 160.2 details the label text requirement.
CFI systems: require motorized dampers that close when ventilation not required, and controls that prevent continuous reliance on the central fan for ventilation. Continuous central fan to provide the required ventilation is explicitly prohibited by the Energy Code amendments.
Accessibility: filters and HRV/ERV cores must be accessible for service from occupiable spaces or within 10 ft of a walking surface (Energy Code requirement).

Exceptions & special cases

Local jurisdiction may allow window‑operation instead of mechanical ventilation only under limited conditions; Appendix E also provides a CMC exception where mechanical ventilation is not required if AHJ permits window ventilation and particular occupancy/condition thresholds are met (e.g., no mechanical cooling and certain climate zones). Check § E 605.1.3 for the exception language.
ASHRAE 62.2 sections excluded by California: the Energy Code lists specific ASHRAE 62.2 sections that are not required for compliance (see § 150.0(o) and its listed exceptions). The Energy Code also amends allowable methods (for example, window operation is not a permissible means under CA amendments in most cases).
For low‑rise HVAC equipment sizing, § E 502.2 limits the scope to smaller single‑phase equipment — for larger or commercial systems use other Appendix sections (E 503, etc.).

If a required numeric factor (for example, the weather/shielding factor wsf) or tabulated occupant factors are needed you must consult ASHRAE 62.2 (the CA rule uses ASHRAE 62.2 values subject to the Energy Code amendments). Those ASHRAE tables are not reproduced in the retrieved California files here, so obtain ASHRAE 62.2 for the detailed factors.

Common mistakes

Assuming window opening counts as compliance everywhere — California amendments prohibit window operation as the whole‑dwelling ventilation method except where the AHJ explicitly allows very limited exceptions. Do not rely on windows unless you confirm the local allowance.
Using continuous central fan operation to meet whole‑house ventilation without the required CFI damper and control features — the Energy Code forbids continuous AHU operation as the sole method in CFI systems. Install motorized dampers and the run‑time tracking required by the amendment.
Forgetting to measure installed airflow — the code requires airflow measurement at the fan inlet/outlet (flow hood or equivalent) and sound ratings per ASHRAE 62.2 procedures (Energy Code § 160.2). Don’t sign off without measured verification.
Incorrectly claiming infiltration credit without a blower‑door test — the infiltration credit Qinf uses the measured Q50; use the E 605.1.3.2 equation and documented blower‑door test to substantiate any credit.

Worked example — single‑family house, compute mechanical ventilation

Scenario: single‑family home, Afloor = 2,000 ft², Nbr = 3 bedrooms. Blower‑door measured Q50 = 300 CFM50. Assume a conservative wsf = 1.0 for this example (actual wsf must come from ASHRAE 62.2). Vertical height between lowest and highest above‑grade points H = 20 ft (Hr = 8.2 ft; z = 0.4 per the formula). Use the CMC Appendix E equations.

Compute Qtot (required total ventilation): Qtot = 0.03 × Afloor + 7.5 × (Nbr + 1)
= 0.03 × 2000 + 7.5 × (3 + 1)
= 60 + 30 = 90 CFM required whole‑dwelling ventilation. § E 605.1.3.1
Estimate Qinf (infiltration credit) by E 605.1.3.2: Qinf = 0.052 × Q50 × wsf × (H/Hr)^z
H/Hr = 20 / 8.2 ≈ 2.439 → (H/Hr)^0.4 ≈ 1.428
Qinf ≈ 0.052 × 300 × 1.0 × 1.428 ≈ 22.3 CFM. § E 605.1.3.2
Mechanical ventilation required = Qtot − Qinf = 90 − 22.3 ≈ 67.7 CFM. Round up and select equipment/fan control to provide the 68–70 CFM continuous (or equivalent intermittent) supply/exhaust as installed and verified. Remember: the actual wsf must be taken from ASHRAE 62.2 and the exact Q50 from the blower‑door test you perform; this example uses assumptions for illustration.

Related provisions (quick list)

California Energy Code — Ventilation & IAQ: § 150.0(o) (requires ASHRAE 62.2 subject to CA amendments).
CMC Chapter 4 applicability & dwelling unit direction: § 401.1 (ventilation air applicability; points to § 405.0 or ASHRAE 62.2).
CMC Appendix E — Dwelling unit ventilation calculation & infiltration: § E 605.1.3 (+ E 605.1.3.1 & E 605.1.3.2).
CMC Appendix E — Bathroom exhaust fan rates and filter minimums: § E 605.2 and § E 605.3 (bathroom rates and filters).
Mechanical Appendix — Low‑rise HVAC equipment scope and system rules: § E 502.2 (equipment limitations, balancing, controls).
Energy Code — measurement, labeling and whole‑dwelling sound/measurement requirements: § 160.2 (details for measurement and labeling).

If you need, I can produce a one‑page printable checklist you can use at plan review or jobsite inspection that maps each required verification item to its controlling § and the evidence to collect (labels, flow measurement reports, blower door results, damper control diagrams, etc.).

Code references

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

CRC § 101.2.2 High relevance — show source text
CFC—25: California Fire Code

101.2.2, 101.4.2, 301.3.1, 302.2, 307.1, 308.1, 802.2.1, 802.2.3, 803.2.3, 803.4.1.1, 803.4.1.2, 803.4.1.3, 803.4.1.4, 803.4.1.5, 803.4.1.6, Table 804.5.1.1(1), 904.1.5, 1011.6.1.1, 1303.1.2, 1305.2.8.1, 1305.2.14, 1305.2.14.1, 1401.2, 1501.1, 1501.5, 1502.1, 1502.1.1, 1502.2, 1502.3, 1504.1, 1507.1, 1507.2

CMC—25: California Mechanical Code

302.2, 702.7, 807.1, 902.1.1, 1008.1, 1305.2.7.1, 1305.2.8, 1305.2.8.1

CPC—25: California Plumbing Code

302.2, 408.1, 702.7, 1009.1, 1009.2, 1009.3, 1009.5, 1302.1.6, 1503.1

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REFERENCED STANDARDS

CRC—25: California Residential Code

101.2, 101.4.1, 104.3.1, 109.3.3, 109.3.10, 302.2, 307.1, 308.1, 401.3, 402.1, 405.2.6, 502.2, 502.3, 502.4, 503.2, 503.3, 503.11, 505.2, 505.3, 507.3, 701.3, 702.4, 702.5, 706.2, 708.1, 805.2, 806.4, 809.1, 906.2, 907.1, 1011.2.1, 1103.1, 1103.2, 1103.3, 1104.1, 1201.4, 1302.1.2, 1302.1.3, 1302.1.3, 1303.1.3, 1401.2, 1402.1, 1402.2, 1402.2.1, 1402.3, 1402.4, 1402.5, 1402.6

ICC 300—2023: ICC Standard on Bleachers, Folding and Telescopic Seating and Grandstands

301.1.1, 401.1.1, 1401.1.1

ICC A117.1—2017: Accessible and Usable Buildings and Facilities
CRC § 6.8 High relevance — show source text
Solar water-heating systems and collectors shall be certified and rated by the Solar Rating and Certification Corporation (SRCC), the International Association of Plumbing and Mechanical Officials, Research and Testing (IAPMO R&T), or by a listing agency that is approved by the executive director. 3. Instantaneous water heaters with an input rating greater than 6.8 kBTU/hr (2kW) shall meet the requirements of Section 110.3(c)6.

(o) Requirements for ventilation and indoor air quality. All dwelling units shall meet the requirements of ASHRAE Standard 62.2. Ventilation and Acceptable Indoor Air Quality in Residential Buildings subject to the amendments specified in Section 150.0(o)1 below. All dwelling units shall comply with Section 150.0(o)2 below.

Exception to Section 150.0(o): The following sections of ASHRAE 62.2 shall not be required for compliance: Section 4.1.1, Section 4.1.2, Section 4.1.4, Section 4.3, Section 4.6, Section 5, Section 6.1.1, Section 6.1.3 and Normative Appendix A.
1. Amendments to ASHRAE 62.2 requirements. A. Window operation. Window operation is not a permissible method of providing the dwelling unit ventilation airflow specified in Section 150.0(o)1C below. B. Central fan integrated (CFI) ventilation systems. CFI ventilation systems shall meet the following requirements. i. Continuous operation prohibition. Continuous operation of a dwelling unit’s central forced air system air handlers used in CFI ventilation systems is not a permissible method of providing the whole-dwelling unit ventilation airflow required in Section 150.0(o)1C. ii. Outdoor air damper(s) . A motorized damper(s) shall be installed on the connected ventilation duct(s) of CFI systems that prevents all airflow into or out of the space-conditioning duct system when the damper(s) is closed.
iii. Damper control . The required motorized damper(s) shall be controlled to be in an opened position when outdoor air ventilation is required for compliance, and shall be in the closed position when ventilation air is not required. The damper(s) shall be closed whenever the space-conditioning system air handling unit is not operating. If the outdoor airflow for the CFI ventilation system is fan-powered, then the outdoor air fan shall not operate when the required motorized damper(s) on the outdoor air ventilation duct(s) is closed. iv. Variable ventilation. CFI ventilation systems shall incorporate controls that track outdoor air ventilation run time, and either open or close the required motorized damper(s) depending on whether or not outdoor air ventilation is required for compliance with Section 150.0(o)1C. During periods when comfort conditioning is not called for by the space-conditioning thermostat, the CFI ventilation system controls shall operate the spaceconditioning system central fan and outdoor air damper(s) when necessary to ensure compliance with the minimum outdoor air ventilation required by Section 150.0(o) in accordance with applicable variable mechanical ventilation methods specified in ASHRAE 62.2 Section 4.5. C. Whole-dwelling unit mechanical ventilation for single-family dwellings. Single-family dwellings shall have mechanical ventilation as specified in Subsections i and iv.
CRC § 416.2 High relevance — show source text
0_
414.0
415.0
416.0 – 416.2
416.3
416.4
417.0
418.0
419.0
Table 4-A
Table 4-B
Table 4-C
Table 402.1
Table 403.7_Notes 11 & 12_

|X|||||||X||||||||||||||||| |Adopting Agency
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended sections
listed below)
Adopt only those sections
that are listed below
Chapter/Section
401.1
401.3
401.3.1
402.1
402.1.2
402.2
402.3
403.0
403.7.2.1 – 403.7.2.4
405.3
406.0
407.0
408.0
409.0
410.0
411.0
412.0
413.0
414.0
415.0
416.0 – 416.2
416.3
416.4
417.0
418.0
419.0
Table 4-A
Table 4-B
Table 4-C
Table 402.1
Table 403.7_Notes 11 & 12_

||||X|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 67

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

68 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 4

VENTILATION AIR

401.0 General.

401.1 Applicability. This chapter contains requirements for ventilation air supply, exhaust, and makeup air requirements for occupiable spaces within a building. [OSHPD 1, 1R, 2, 3, 4 & 5] See Sections 406.0 through 419.0. [SFM] Air filters shall comply with all requirements of Part 12, Title 24, Chap- ter 12-71, SFM Standard 12-71-1. Spaces within buildings, except those within a dwelling unit in residential occupancies where occupants are nontransient, shall comply with Section 402.0 through Section 404.0. Requirements for ventilation air rate for dwelling units in residential occupancies, where the occupants are nontransient, shall be in accordance with Section 405.0 or ASHRAE 62.2.
CRC § 6.8 High relevance — show source text
A reserved single pole circuit breaker space in the electrical panel adjacent to the circuit breaker for the branch circuit in A above and labeled with the words “Future 240V Use”; and iv. A condensate drain that is no more than 2 inches higher than the base of the installed water heater, and allows natural draining without pump assistance. B. If the designated space is more than 3 feet from the water heater, then this space shall include the following: i. A dedicated 240 volt branch circuit shall be installed within 3 feet from the designated space. The branch circuit shall be rated at 30 amps minimum. The blank cover shall be identified as “240V ready”; and ii. The main electrical service panel shall have a reserved space to allow for the installation of a double pole circuit breaker for a future HPWH installation. The reserved space shall be permanently marked as “For Future 240V use”; and

iii. Either a dedicated cold water supply, or the cold water supply shall pass through the designated HPWH location just before reaching the gas or propane water heater; and

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iv. The hot water supply pipe coming out of the gas or propane water heater shall be routed first through the designated HPWH location before serving any fixtures; and v. The hot and cold water piping at the designated HPWH location shall be exposed and readily accessible for future installation of an HPWH; and vi. A condensate drain that is no more than 2 inches higher than the base of the installed water heater, and allows natural draining without pump assistance. 2. Solar water-heating systems and collectors shall be certified and rated by the Solar Rating and Certification Corporation (SRCC), the International Association of Plumbing and Mechanical Officials, Research and Testing (IAPMO R&T), or by a listing agency that is approved by the executive director. 3. Instantaneous water heaters with an input rating greater than 6.8 kBTU/hr (2kW) shall meet the requirements of Section 110.3(c)6.

(o) Requirements for ventilation and indoor air quality. All dwelling units shall meet the requirements of ASHRAE Standard 62.2. Ventilation and Acceptable Indoor Air Quality in Residential Buildings subject to the amendments specified in Section 150.0(o)1 below. All dwelling units shall comply with Section 150.0(o)2 below.

Exception to Section 150.0(o): The following sections of ASHRAE 62.2 shall not be required for compliance: Section 4.1.1, Section 4.1.2, Section 4.1.4, Section 4.3, Section 4.6, Section 5, Section 6.1.1, Section 6.1.3 and Normative Appendix A.
1. Amendments to ASHRAE 62.2 requirements. A. Window operation. Window operation is not a permissible method of providing the dwelling unit ventilation airflow specified in Section 150.0(o)1C below. B. Central fan integrated (CFI) ventilation systems. CFI ventilation systems shall meet the following requirements. i. Continuous operation prohibition. Continuous operation of a dwelling unit’s central forced air system air handlers used in CFI ventilation systems is not a permissible method of providing the whole-dwelling unit ventilation airflow required in Section 150.0(o)1C. ii.
CRC § 160.3 High relevance — show source text
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.

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.

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MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS
1. Outdoor condensing units . A. Clearances. Installed air conditioner and heat pump outdoor condensing units shall have a clearance of at least 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. Air-distribution and ventilation system ducts, plenums and fans. A. CMC compliance.
i. All air-distribution system ducts and plenums, including, but not limited to, mechanical closets and air-handler boxes, shall meet the requirements of the CMC Sections 601.0, 602.0, 603.0, 604.0 and 605.0 and ANSI/SMACNA006-2006 HVAC Duct Construction Standards Metal and Flexible 3rd Edition, incorporated herein by reference. ii. Portions of supply-air and return-air ducts and plenums of a space heating or cooling system shall be insulated in accordance with either Subsection a or b below:

a. Ducts shall have a minimum installed level of R-6.0, or
CRC § 150.0 High relevance — show source text
Forward phase cut dimmers controlling LED light sources in these spaces shall comply with NEMA SSL 7A. Exception 1 to Section 150.0(k)2F: Ceiling fans may provide control of integrated lighting via a remote control. Lighting integral to kitchen range hoods and bathroom exhaust fans. Exception 2 to Section 150.0(k)2F: Luminaires connected to a circuit with controlled lighting power less than 20 watts or controlled by an occupancy or vacancy sensor providing automatic-off functionality. Exception 3 to Section 150.0(k)2F: Navigation lighting rated less than 5 watts, such as night lights, step lights, and path lights. Lighting controlled by automatic-off controls and located internal to drawers, cabinetry with opaque fronts, or cabinetry with doors. G. Independent controls. Lighting integrated with the exhaust fans shall be controlled independently from the fans. The following shall be controlled separately from ceiling-installed lighting such that one can be turned on without turning on the other: i. Undercabinet lighting. ii. Undershelf lighting. iii. Interior lighting of display cabinets.

iv. Switched outlets.
1. Residential outdoor lighting. In addition to meeting the requirements of Section 150.0(k)1A, luminaires providing residential outdoor lighting shall meet the following requirements, as applicable: A. Outdoor lighting permanently mounted to a residential building or to other buildings on the same lot shall meet the following requirements: i. Controlled by a manual ON and OFF control switch that permits the automatic actions of Item ii below; and ii. Controlled by one of the following controls: a. A photocell and a motion sensor; or b. A photocell and an automatic time switch control; or c. Controlled by an astronomical time clock control. B. Controls that override to ON shall not be allowed unless the override automatically returns the automatic control to its normal operation within 6 hours. C. An energy management control system (EMCS) or other controls that provides the specified lighting control functionality and complies with all requirements applicable to the specified controls may be used to meet these requirements.
2. Internally illuminated address signs. Internally illuminated address signs shall either: A. Comply with Section 140.8; or B. Consume no more than 5 watts of power.
3. Residential garages for eight or more vehicles. Lighting for residential parking garages for eight or more vehicles shall comply with the applicable requirements for nonresidential garages in Sections 110.9, 130.0, 130.1, 130.4, 140.6 and 141.0.
(l) Reserved.

(m) Air-distribution and ventilation system ducts, plenums and fans.
1. CMC compliance.
A. All air-distribution system ducts and plenums, including but not limited to, mechanical closets and air-handler boxes, shall meet the requirements of the CMC Sections 601.0, 602.0, 603.0, 604.0, 605.0 and ANSI/SMACNA-006-2006 HVAC Duct Construction Standards Metal and Flexible, 3rd Edition, incorporated herein by reference.

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B. Portions of supply-air and return-air ducts and plenums of a space heating or cooling system shall be insulated in accordance with either Subsection i or ii below:
CRC § 1.11.3.4 High relevance — show source text
Plans and spec-_ ifications shall be prepared by an engineer duly qualified in that branch of engineering necessary to perform such services. Administration of the work of construction shall be under the charge of the responsible architect or engineer except that where plans and specifications involve alterations or repairs, such work of construction may be administered by an engi- neer duly qualified to perform such services and holding a valid certificate under Chapter 7 (commencing with Section 65700) of Division 3 of the Business and Professions Code for performance of services in that branch of engineering in which said plans, specifications and estimates and work of construction are applicable.

This section shall not be construed as preventing the design of fire-extinguishing systems by persons holding a C-16 license issued pursuant to Division 3, Chapter 9, Business and Professions Code. In such instances, however, the responsibility charge of this section shall prevail.

1.11.3.4 Existing high-rise buildings. 1. Complete plans or specifications, or both, shall be prepared covering all work required by California Fire Code Chapter 11 and California Existing Building Code for existing high-rise buildings. Such plans or specifications shall be submitted to the enforcing agency having jurisdiction. 2. When new construction is required to conform with the provisions of these regulations, complete plans or specifications, or both, shall be prepared in accordance with the provisions of this subsection. As used in this section, “new construction” is not intended to include repairs, replacements or minor alterations which do not disrupt or appreciably add to or affect the structural aspects of the building.

1.11.3.5 Retention of plans. Refer to Building Standards Law, Health and Safety Code Sections 19850 and 19851 for permanent retention of plans.

1.11.4 Fees.

1.11.4.1 Other fees. Pursuant to Health and Safety Code Section 13146.2, a city, county or district which inspects a hotel, motel, lodg- ing house or apartment house may charge and collect a fee for the inspection from the owner of the structure in an amount, as determined by the city, county or district, sufficient to pay its costs of that inspection.

1.11.4.2 Large family day-care. Pursuant to Health and Safety Code Section 1597.46, Large Family Day-Care Homes, the local government shall process any required permit as economically as possible, and fees charged for review shall not exceed the costs of the review and permit process.

1.11.4.3 High-Rise. Pursuant to Health and Safety Code Section 13217, High-Rise Structure Inspection: Fees and costs, a local agency which inspects a high-rise structure pursuant to Health and Safety Code Section 13217 may charge and collect a fee for the inspection from the owner of the high-rise structure in an amount, as determined by the local agency, sufficient to pay its costs of that inspection.

_**1.11.4.4 Fire clearance pre-inspection.
CRC § 403.3 High relevance — show source text
403.3 Single-Zone Systems. For ventilation systems where one or more air handlers supply a mixture of outdoor air and recirculated air to only one ventilation zone, the outdoor air intake flow ( Vot ) shall be determined in accordance with Equation 403.3. [ASHRAE 62.1:6.2.2]

Vot = Voz (Equation 403.3)

403.4 One Hundred Percent Outdoor Air Systems. For ventilation systems where one or more air handlers supply only outdoor air to one or more ventilation zones, the outdoor air intake flow ( Vot ) shall be determined in accordance with Equation 403.4. [ASHRAE 62.1:6.2.3]

Vot = ∑ all zones Voz (Equation 403.4)

403.5 Multiple-Zone Recirculating Systems. For ventilation systems where one or more air handlers supply a mixture of outdoor air and recirculated air to more than one ventilation zone, the outdoor air intake flow ( Vot ) shall be determined in accordance with Section 403.5.1 through Section 403.5.2. [ASHRAE 62.1:6.2.4]

403.5.1 Uncorrected Outdoor Air Intake. The uncorrected outdoor air intake ( Vou ) flow shall be determined in accordance with Equation 403.5.1. [ASHRAE 62.1:6.2.4.1]

(Equation 403.5.1) Vou = D ∑ all zones ( Rp•Pz ) + ∑ all zones ( Ra•Az )

403.5.1.1 Occupant Diversity. The occupant diversity ratio ( D) shall be determined in accordance with Equation 403.5.1.1 to account for variations in population within the ventilation zones served by the system.

(Equation 403.5.1.1) D = Ps / ∑ all zones Pz

Where the system population ( Ps ) is the total population in the area served by the system.

2025 CALIFORNIA MECHANICAL CODE 73

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

VENTILATION AIR

Exception: Alternative methods to account for occupant diversity shall be permitted, provided that the resulting ( Vou ) value is not less than that determined in accordance with Equation 403.5.1.

[ASHRAE 62.1:6.2.4.1.1]

403.5.1.2 System Ventilation Efficiency. The system ventilation efficiency ( Ev ) shall be determined in accordance with Section 403.5.1.3 for the

simplified procedure or Section 404.0 for the alternate procedure. These procedures also establish zone minimum primary airflow rates for VAV systems.

[ASHRAE 62.1:6.2.4.2]

403.5.1.3 Simplified Procedure for System Ventilation Efficiency. System ventilation efficiency ( Ev ) shall be determined in accordance with Equation 403.5.1.3(1) or Equation 403.5.1.3(2).
CRC § 140.8 High relevance — show source text
C. An energy management control system (EMCS) or other controls that provides the specified lighting control functionality and complies with all requirements applicable to the specified controls may be used to meet these requirements. 4. Internally illuminated address signs. Internally illuminated address signs shall either: A. Comply with Section 140.8; or B. Consume no more than 5 watts of power. 5. Residential garages for eight or more vehicles. Lighting for residential parking garages for eight or more vehicles shall comply with the applicable requirements for nonresidential garages in Sections 110.9, 130.0, 130.1, 130.4, 140.6 and 141.0.

(l) Reserved.

(m) Air-distribution and ventilation system ducts, plenums and fans.
1. CMC compliance.
A. All air-distribution system ducts and plenums, including but not limited to, mechanical closets and air-handler boxes, shall meet the requirements of the CMC Sections 601.0, 602.0, 603.0, 604.0, 605.0 and ANSI/SMACNA-006-2006 HVAC Duct Construction Standards Metal and Flexible, 3rd Edition, incorporated herein by reference.

2025 CALIFORNIA ENERGY CODE 163

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SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

B. Portions of supply-air and return-air ducts and plenums of a space heating or cooling system shall be insulated in accordance with either Subsection i or ii below:

i. Ducts shall have a minimum installed level of R-6.0, or Exception 1 to Section 150.0(m)1Bi: Portions of the duct system located in conditioned space below the ceiling separating the occupiable space from the attic are not required to be insulated if all of the following conditions are met:

a. The noninsulated portion of the duct system is located entirely inside the building’s thermal envelope as confirmed by visual inspection. b. At all locations where noninsulated portions of the duct system penetrate into unconditioned space, the penetration shall be draft stopped compliant with CFC Sections 703.1 and 704.1 and air-sealed to the construction materials that are penetrated, using materials compliant with CMC Section E502.4.2 to prevent air infiltration into the cavity. All connections in unconditioned space are insulated to a minimum of R-6.0 as confirmed by visual inspection. Exception 2 to Section 150.0(m)1Bi : Ducts located in an unvented attic shall have a minimum insulation value of R-4.2, verified by visual inspection where:

a. The attic has at least R-30 insulation between the roof rafters in contact with the roof deck.

b. The gable ends meet the wall insulation requirements of Section 150.1(c)1B. c. The dwelling unit achieves a whole building leakage rate of 3.0 ACH50 or less, as confirmed by field verification and diagnostic testing in accordance with Reference Residential Appendix RA3.8. ii. Ducts do not require insulation when the duct system is located entirely within conditioned space, as confirmed through field verification and diagnostic testing in accordance with the requirements of Reference Residential Appendix RA3.1.4.3.8. For dwelling units with attics, the duct system shall be located below the ceiling separating the occupiable space from the attic.
CRC § 90.1 High relevance — show source text
[ASHRAE 90.1:6.5.2.2]

E 503.5.5.2.1 Three-Pipe System. Hydronic systems that use a common return system for both hot water and chilled water shall not be used. [ASHRAE 90.1:6.5.2.2.1]

E 503.5.5.2.2 Two-Pipe Changeover Sys- tem. Systems that use a common distribution system to supply both heated and chilled water are acceptable where in accordance with the following:

(1) The system is designed to allow a dead band between changeover from one mode to the other of not less than 15°F (8°C) outdoor air temperature.

(2) The system is designed to operate and is provided with controls that will allow operation in one mode for not less than 4 hours before changing over to the other mode.

(3) Reset controls are provided that allow heating and cooling supply temperatures at the changeover point to be not more than 30°F (17°C) apart. [ASHRAE 90.1:6.5.2.2.2]

E 503.5.5.2.3 Hydronic (Water Loop) Heat Pump Systems. Hydronic heat pumps connected to a common heat pump water loop with central devices for heat rejection (e.g., cooling tower) and heat addition (e.g., boiler) shall have the following:

(1) Controls that are capable of and configured to provide a heat pump water supply temperature dead band of at least 20°F (11°C) between initiation of heat rejection and heat addition by the central devices (e.g., tower and boiler).

(2) For climate zone 3 through zone 8, where a closed-circuit cooling tower (fluid cooler) is used, either an automatic valve shall be installed to bypass all but a minimal flow of water around the tower (for freeze protection) or low-leakage positive closure dampers shall be provided. Where an opencircuit cooling tower is used directly in the heat pump loop, an automatic valve shall be installed to bypass all heat pump water flow around the tower. Where an open-circuit cooling tower is used in conjunction with a separate heat exchanger to isolate the tower from the heat pump loop then heat loss shall be controlled by shutting down the circulation pump on the cooling tower loop.

Exception: Where a system loop temperature optimization controller is used to determine the most efficient operating temperature based on real-time conditions of demand and capacity, dead bands of less than 20°F (11°C) shall be permitted.

[ASHRAE 90.1:6.5.2.2.3]

E 503.5.5.3 Dehumidification. Where humidity controls are provided, such controls shall prevent reheating, mixing of hot and cold airstreams, or other means of simultaneous heating and cooling of the same airstream.

Exceptions:

(1) The system is capable of and configured to reduce supply air volume to 50 percent or less of the design airflow rate or the minimum outdoor air ventilation rate in accordance with Chapter 4 or ASHRAE 62.1 or other applicable federal, state, or local code or recognized standard, whichever is larger before simultaneous heating and cooling takes place.
CRC § 1112.12.4. High relevance — show source text
( P [2] 0 P 22 ) d - ln ( P0P2 )

f - C [2] r 6 - f

2025 CALIFORNIA MECHANICAL CODE 243

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

REFRIGERATION

expected to operate simultaneously, connect to a common discharge pipe, the common pipe shall be sized large enough to prevent the back pressure at each pressure-relief device from exceeding the maximum allowable back pressure in accordance with Section 1112.12.4.

[ASHRAE 15:9.7.9.3.3]

1112.13 Rating of Pressure-Relief Device. The rated discharge capacity of a pressure-relief device expressed in pounds of air per minute (kg/s), shall be determined in accordance with ASME BPVC Section VIII.1. Pipe and fittings between the pressure-relief valve and the parts of the system it protects shall have not less than the area of the pressurerelief valve inlet area. [ASHRAE 15:9.7.6]

1112.14 Rating of Rupture Members and Fusible Plugs. The rated discharge capacity of a rupture member or fusible plug discharging to the atmosphere under critical flow conditions, in pounds of air per minute (kg/s), shall be determined in accordance with the following formulas:

C = 0.64 P l d [2] [Equation 1112.14(1)]

d = 1.25 √ C / P l [Equation 1112.14(2)]

Where:

C = Rated discharge capacity expressed as mass flow of air, pounds per minute.

d = Smallest of the internal diameter of the inlet pipe, retaining flanges, fusible plug, and rupture member , inches.

For rupture members:

[Equation 1112.14(3)]

P1 = (rated pressure in psig x 1.1) + 14.7 psia

For fusible plugs:

P1 = Absolute saturation pressure corresponding to the stamped temperature melting point of the fusible plug or the critical pressure of the refrigerant used, whichever is smaller, pound-force per square inch atmosphere, psia. [ASHRAE 15:9.7.7]

For SI units:1 pound per minute = 0.00756 kg/s

1113.0 Overpressure Protection.

1113.1 General. Pressure vessels shall be provided with overpressure protection in accordance with ASME BPVC Section VIII.1. Pressure vessels containing liquid refrigerant that are capable of being isolated by stop valves from other parts of a refrigerating system shall be provided with overpressure protection. Pressure relief devices or fusible plugs shall be sized in accordance with Section 1113.5. [ASHRAE 15:9.7.1, 9.7.2]

»

Unless the maximum allowable back pressure ( P0 ) is specified by the relief valve manufacturer, the following maximum allowable back pressure values shall be used for P0, where P is the set pressure and Pa is atmospheric pressure at the nominal elevation of the installation (see Table 1112.12.4):
CRC § 345-357. High relevance — show source text
RESOURCE A-116 2025 CALIFORNIA EXISTING BUILDING CODE

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

RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES
1. Wardle, T. M. “Notes on the Fire Resistance of Heavy Timber Construction,” Information Series, No. 53, New Zealand Forest Service, Wellington, 1966.
2. Fisher, R. W., and Smart, P. M. T., “Results of Fire Resistance Tests on Elements of Building Construction,” Building Research Establishment Report, G R6, London, HMSO, 1975.
3. Serex, E. R., “Fire Resistance of Alta Bates Gypsum Block Non-Load Bearing Wall,” Report to Alta Bates Community Hospital, Structural Research Laboratory Report, ES-7000, University of Calif., Berkeley, 1969.
4. Thomas, F. G., and Webster, C. T., “Investigations on Building Fires, Part VI: The Fire Resistance of Reinforced Concrete Columns,” National Building Studies, Research Paper, No. 18, Dept. of Scientific and Industrial Research (Building Research Station), London, HMSO, 1953.
5. Building Research Establishment, “Timber Fire Doors,” Digest, 220, Borehamwood, Nov. 1978.
6. Massachusetts State Building Code; Recommended Provisions, Article 22: Repairs, Alterations, Additions, and Change of Use of Existing Buildings, Boston, Oct. 23, 1978.
7. Freitag, J. K., Architectural Engineering; with Especial Reference to High Building Construction, Including Many Examples of Prominent Office Buildings, 2nd ed., rewritten, J. Wiley, New York, 1906.
8. Architectural Record, Sweet’s Indexed Catalogue of Building Construction for the Year 1906, New York, 1906.
9. Dept. of Commerce, Building Code Committee, “Recommended Minimum Requirements for Fire Resistance in Buildings,” Building and Housing, No. 14, National Bureau of Standards, Washington, 1931.
10. British Standards Institution, “Fire Tests on Building Materials and Structures,” British Standards, 476, Pt. 1, London,
12. Lonberg-Holm, K., “Glass,” The Architectural Record, Oct. 1930, pp. 345-357.
13. Structural Clay Products Institute, “Fire Resistance,” Technical Notes on Brick and Tile Construction, 16 rev., Washington,
15. Ramsey, C. G., and Sleeper, H. R., Architectural Graphic Standards for Architects, Engineers, Decorators, Builders, and Draftsmen, 3rd ed., J. Wiley, New York, 1941.
16. Underwriters’ Laboratories, Fire Protection Equipment List, Chicago, Jan. 1957.
17. Underwriters’ Laboratories, Fire Resistance Directory; with Hourly Ratings for Beams, Columns, Floors, Roofs, Walls, and Partitions, Chicago, Jan. 1977.
18. Mitchell, N. D., “Fire Tests of Gunite Slabs and Partitions,” Building Materials and Structures, Report BMS 131, National Bureau of Standards, Washington, May 1952.
CRC § 2.3 Medium relevance — show source text
ANSI Z21.47 is the American National Standards Institute document titled “Gas-Fired Central Furnaces,” 2021 (ANSI Z21.472021/CSA 2.3-2021).

ANSI Z83.8 is the American National Standards Institute document titled “Gas Unit Heaters, Gas Packaged Heaters, Gas Utility Heaters and Gas-Fired Duct Furnaces,” 2016 (ANSI Z83.8-2016/CSA 2.6-2016 (R2021)).

APPLIANCE EFFICIENCY REGULATIONS are the regulations in Title 20, Sections 1601 et seq. of the California Code of Regulations.

APPROVED CALCULATION METHOD (See “alternative calculation methods.”)

ASCE 7-16 is the American Society of Civil Engineers Standard 7-16.

ASHRAE is the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

ASHRAE CLIMATIC DATA FOR REGION X is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ASHRAE Climatic Data for Region X, Arizona, California, Hawaii and Nevada,” Publication SPCDX, 1982 and “Supplement,” 1994.

ASHRAE HANDBOOK, APPLICATIONS VOLUME is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ASHRAE Handbook: Heating, Ventilating, and Air-Conditioning Applications” (I-P) (2019).

ASHRAE HANDBOOK, FUNDAMENTALS VOLUME is the American Society of Heating, Refrigerating and Air- Conditioning Engineers document titled “ASHRAE Handbook: Fundamentals” (I-P) (2017).

ASHRAE HANDBOOK, SYSTEMS AND EQUIPMENT VOLUME is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ASHRAE Handbook: Heating, Ventilating, and Air-Conditioning Systems and Equipment” (I-P) (2020).

ASHRAE GUIDELINE 36 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “HighPerformance Sequences of Operation for HVAC Systems,” 2021 (ASHRAE Guideline 36-2021).

ASHRAE STANDARD 52.2 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size,” 2017 (ANSI/ASHRAE Standard 52.2-2017).

ASHRAE STANDARD 55 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Thermal Environmental Conditions for Human Occupancy,” 2020 (ANSI/ASHRAE Standard 55-2020).

ASHRAE STANDARD 62.1 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ Ventilation for Acceptable Indoor Air Quality,” 2019 (ANSI/ASHRAE Standard 62.1-2022, including Addenda y, ao, P, B).

ASHRAE STANDARD 62.2 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Ventilation and Acceptable Indoor Air Quality in Residential Buildings,” 2022 (ANSI/ASHRAE Standard 62.2-2022).
CRC § 36-2021 Medium relevance — show source text
ASHRAE HANDBOOK, SYSTEMS AND EQUIPMENT VOLUME is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ASHRAE Handbook: Heating, Ventilating, and Air-Conditioning Systems and Equipment” (I-P) (2020).

ASHRAE GUIDELINE 36 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “HighPerformance Sequences of Operation for HVAC Systems,” 2021 (ASHRAE Guideline 36-2021).

ASHRAE STANDARD 52.2 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size,” 2017 (ANSI/ASHRAE Standard 52.2-2017).

ASHRAE STANDARD 55 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Thermal Environmental Conditions for Human Occupancy,” 2020 (ANSI/ASHRAE Standard 55-2020).

ASHRAE STANDARD 62.1 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “ Ventilation for Acceptable Indoor Air Quality,” 2019 (ANSI/ASHRAE Standard 62.1-2022, including Addenda y, ao, P, B).

ASHRAE STANDARD 62.2 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Ventilation and Acceptable Indoor Air Quality in Residential Buildings,” 2022 (ANSI/ASHRAE Standard 62.2-2022).

ASHRAE STANDARD 84 is the American National Standards Institute/American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Method of Testing Air-to-Air Heat/Energy Exchangers,” 2020 (ANSI/ASHRAE 84-2020).

ASHRAE STANDARD 90.1 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Energy Standards for Buildings Except Low-Rise Residential Buildings,” 2019 (ANSI/ASHRAE/IES Standards 90.1-2019).

ASHRAE STANDARD 154 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Ventilation for Commercial Cooking Operations,” 2016 (ANSI/ASHRAE Standard 154-2016).

ASHRAE STANDARD 193 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers document titled “Method of Test for Determining the Airtightness of HVAC Equipment,” RA2014 (ANSI/ASHRAE Standard 193-RA2014).

ASME is the American Society of Mechanical Engineers.

ASME A17.1/CSA B44 is the American Society of Mechanical Engineers document titled “Safety Code for Elevators and Escalators,” 2019 (ASME A17.1-2019/CSA B44-2019).

ASME A112.18.1/CSA B125.1 is the American Society of Mechanical Engineers document titled “Plumbing Supply Fittings,” 2018 (ASME A112.18.1-2018/CSA B125.1-18).

ASTM is the American Society for Testing and Materials International.

ASTM C55 is the American Society for Testing and Materials document titled “Standard Specifications for Concrete Building Brick,” 2017 (ASTM C55-17).

CRC § 920-2020 Medium relevance — show source text

378 2025 CALIFORNIA MECHANICAL CODE

REFERENCED STANDARDS

TABLE 1801.2 (continued) « STANDARDS, PUBLICATIONS, PRACTICES, AND GUIDES

DOCUMENT NUMBER	DOCUMENT TITLE	APPLICATION
ASHRAE 62.2-2022	Ventilation and Acceptable Indoor Air Quality in Residential Buildings	Ventilation
ANSI/ASHRAE/IES 90.1- 2019	Energy Standard for Buildings Except Low-Rise Residential Buildings (with Addenda a and d)	Energy
ASHRAE/IES 90.2-2018	Energy-Efficient Design of Low-Rise Residential Buildings	Energy, Dwellings
ASHRAE 90.4-2019	Energy Standard for Data Centers	Data Centers
ASHRAE 127-2020	Method of Testing for Rating Air-Conditioning Units Serving Data Center (DC) and Other Information Technology Equipment (ITE) Spaces	Air Conditioners
ASHRAE 129-1997 (R2002)	Measuring Air-Change Effectiveness	Air Change Effectiveness
ASHRAE GRP 158-1979	Cooling and Heating Load Calculation Manual	Ventilation
ASHRAE 169-2021	Climatic Data for Building Design Standards	Miscellaneous
ASHRAE/ACCA 183- 2007 (R2020)	Peak Cooling and Heating Load Calculations in Buildings Except Low- Rise Residential Buildings	Cooling and Heating Load,

CRC § 1801.2 Medium relevance — show source text

378 2025 CALIFORNIA MECHANICAL CODE

REFERENCED STANDARDS

TABLE 1801.2 (continued) « STANDARDS, PUBLICATIONS, PRACTICES, AND GUIDES

DOCUMENT NUMBER	DOCUMENT TITLE	APPLICATION
ASHRAE 62.2-2022	Ventilation and Acceptable Indoor Air Quality in Residential Buildings	Ventilation
ANSI/ASHRAE/IES 90.1- 2019	Energy Standard for Buildings Except Low-Rise Residential Buildings (with Addenda a and d)	Energy
ASHRAE/IES 90.2-2018	Energy-Efficient Design of Low-Rise Residential Buildings	Energy, Dwellings
ASHRAE 90.4-2019	Energy Standard for Data Centers	Data Centers
ASHRAE 127-2020	Method of Testing for Rating Air-Conditioning Units Serving Data Center (DC) and Other Information Technology Equipment (ITE) Spaces	Air Conditioners
ASHRAE 129-1997 (R2002)	Measuring Air-Change Effectiveness	Air Change Effectiveness
ASHRAE GRP 158-1979	Cooling and Heating Load Calculation Manual	Ventilation
ASHRAE 169-2021	Climatic Data for Building Design Standards	Miscellaneous
ASHRAE/ACCA 183- 2007 (R2020)	Peak Cooling and Heating Load Calculations in Buildings Except Low- Rise Residential Buildings	Cooling and Heating Load, Miscellaneous
ASHRAE Handbook-2020	HVAC Systems and Equipment	Design
ASHRAE Indoor Air Quality Guide	Indoor Air Quality Guide: Best Practices for Design, Construction, and Com- missioning	Ventilation
ASME	ASME	ASME
ASME A13.1-2020	Scheme for the Identification of Piping Systems	Piping
ASME A112.18.6/CSA B125.6-2017 (R2021)	Flexible Water Connectors	Piping
ASME B1.20.3-1976 (R2018)	Dryseal Pipe Threads (Inch)	Joints
ASSE	ASSE	ASSE
ASSE/IAPMO/ANSI Series 12000-2021	Professional Qualifications Standard for Water Management and Infection Control Risk Assessment for Building Systems	Professional Qualifications
ASSE 12010-2021	Environment of Care, Infection Control and Construction Risk Assessment Professional Qualification Standard	Professional Qualifications
ASSE 12020-2021	Environment of Care, Infection Control and Construction Risk Assessment Professional Qualification Standard for Construction and Maintenance Employers	Professional Qualifications
ASSE 12062-2021	Water Quality Program Professional Qualifications Standard for Pipefitters and HVAC Technicians	Professional Qualifications
ASSE 12080-2021	Professional Qualifications Standard for Legionella Water Safety and Manage- ment Specialist	Professional Qualifications
ASSE/IAPMO/ANSI Series 13000-2015 (R2020)	Service Plumber and Residential Mechanical Service Technician Professional Qualifications Standard	Professional Qualifications
ASSE/IAPMO/ANSI 13020- 2015 (R2020)	Professional Qualifications Standard

CRC § 6-2021 Medium relevance — show source text
ANSI/NEMA WD 6-2021 Wiring Devices—Dimensional Specifications

ANSI Z21.40.4a-1998 (R2022)/CGA 2.94a-M98 (R2022) Performance Testing and Rating of Gas-Fired, Air-Conditioning and Heat Pump Appliances

ANSI Z21.47-2021/CSA 2.3:21 Gas-Fired Central Furnaces

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STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

ANSI Z83.8-2016/CSA 2.6-2016 (R2021)

Gas Unit Heaters, Gas Packaged Heaters, Gas Utility Heaters and Gas-Fired Duct Furnaces (2016)

Available from:

American National Standards Institute 25 West 43rd Street, 4th floor New York, NY 10036 (212) 642-4900

ANSI/APSP/ICC-5-2011 American National Standard For Residential Inground Swimming Pools (2011 w/Addendum A)

Available from: Association of Pool & Spa Professionals 2111 Eisenhower Ave. Alexandria, VA 22314 (703) 838-0083

AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS (NATIONAL PUBLICATIONS)

ASHRAE GUIDELINE 36-2021 High-Performance Sequences of Operation for HVAC Systems

ANSI/ASHRAE Standard 52.2-2017

Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size

ANSI/ASHRAE Standard 55-2023

Thermal Environment Conditions for Human Occupancy

ANSI/ASHRAE Standard 62.1-2022 Ventilation and Acceptable Indoor Air Quality

ANSI/ASHRAE Standard 62.2-2022

Ventilation and Acceptable Indoor Air Quality in Residential Buildings

ANSI/ASHRAE Standard 84-2020 Method of Testing Air-to-Air Heat/Energy Exchangers

ANSI/ASHRAE/IES Standards 90.1-2022 Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings

ANSI/ASHRAE Standard 154-2022 Ventilation for Commercial Cooking Operations

ANSI/ASHRAE Standard 193-2010 (RA2014) Method of Test for Determining the Airtightness of HVAC Equipment

ASHRAE Handbooks

2023 ASHRAE Handbook - HVAC Applications Inch-Pound Edition

2020 ASHRAE Handbook - HVAC Systems and Equipment I-P Edition

2021 ASHRAE Handbook - Fundamentals I-P Edition

Available from: American Society of Heating,
```
                         Refrigerating and Air Conditioning Engineers
```
(ASHRAE) 1791 Tullie Circle N.E. Atlanta, GA 30329 www.ashrae.org

AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS (REGIONAL PUBLICATION)

ASHRAE Climatic Data for Region X Arizona, California, Hawaii, Nevada, Publication SPCDX, 1982, ISBN #20002196 and Supplement, 1994, ISBN #20002596

Available from: Order Desk Building News 10801 National Boulevard Los Angeles, CA 90064 (800) 873-6397 or (310) 474-7771 www.bnibooks.com/
CRC § 62.1 Medium relevance — show source text
Thermal Environment Conditions for Human Occupancy

ANSI/ASHRAE Standard 62.1-2022 Ventilation and Acceptable Indoor Air Quality

ANSI/ASHRAE Standard 62.2-2022

Ventilation and Acceptable Indoor Air Quality in Residential Buildings

ANSI/ASHRAE Standard 84-2020 Method of Testing Air-to-Air Heat/Energy Exchangers

ANSI/ASHRAE/IES Standards 90.1-2022 Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings

ANSI/ASHRAE Standard 154-2022 Ventilation for Commercial Cooking Operations

ANSI/ASHRAE Standard 193-2010 (RA2014) Method of Test for Determining the Airtightness of HVAC Equipment

ASHRAE Handbooks

2023 ASHRAE Handbook - HVAC Applications Inch-Pound Edition

2020 ASHRAE Handbook - HVAC Systems and Equipment I-P Edition

2021 ASHRAE Handbook - Fundamentals I-P Edition

Available from: American Society of Heating,
```
                         Refrigerating and Air Conditioning Engineers
```
(ASHRAE) 1791 Tullie Circle N.E. Atlanta, GA 30329 www.ashrae.org

AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS (REGIONAL PUBLICATION)

ASHRAE Climatic Data for Region X Arizona, California, Hawaii, Nevada, Publication SPCDX, 1982, ISBN #20002196 and Supplement, 1994, ISBN #20002596

Available from: Order Desk Building News 10801 National Boulevard Los Angeles, CA 90064 (800) 873-6397 or (310) 474-7771 www.bnibooks.com/

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STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

AMERICAN SOCIETY OF MECHANICAL ENGINEERS

ASME A17.1-2019/CSA B44:19 Safety Code for Elevators and Escalators

ASME A112.18.1-2018/CSA B125.1-18

Plumbing supply fittings

Available from:

ASME

Two Park Avenue New York, NY 10016-5990 (800) 843-2763 http://www.asme.org/

AMERICAN SOCIETY FOR TESTING AND MATERIALS/ASTM INTERNATIONAL

ASTM C55-17 Standard Specification for Concrete Building Brick (2017)

ASTM C177-19e1 Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus

ASTM C272/C272M-18 Standard Test Method for Water Absorption of Core Materials for Sandwich Constructions

ASTM C335/C335M-23 Standard Test Method for Steady-State Heat Transfer Properties of Horizontal Pipe Insulation

ASTM C518-21 Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus

ASTM C731-15 (2022) Standard Test Method for Extrudability, After Package Aging, of Latex Sealants

ASTM C732-17 (2022) Standard Test Method for Aging Effects of Artificial Weathering on Latex Sealants

ASTM C836/C836M-18 (2022) Standard Specification for High Solids Content, Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course
CRC § 62.2 Medium relevance — show source text
[ASHRAE 62.2:4.6] E 605.2 Bathroom Exhaust Fans. Except where a whole house energy recovery system is used, a mechanical exhaust fan vented to the outdoors shall be provided in each room containing a bathtub, shower, or tub/shower combination. The ventilation rate shall be not less than 50 ft [3] /min (0.02 m [3] /s) for intermittent operation and 20 ft [3] /min (0.009 m [3] /s) for continuous operation. Fans shall comply with the Energy Star Program.

E 605.3 Filters. Heating and air conditioning filters shall have a MERV rating of 6 or higher. The air distribution system shall be designed for the pressure drop across the filter.

E 606.0 Indoor Air Quality for Other than Low-Rise Residential Buildings.

E 606.1 Minimum Indoor Air Quality. The building shall comply with Chapter 4 or ASHRAE 62.1 for ventilation air supply.

E 607.0 Environmental Comfort.

E 607.1 Thermal Comfort Controls. The mechanical systems and controls of building shall be designed to provide and maintain indoor comfort conditions in accordance with

ASHRAE 55.

E 607.2 Heating and Air-Conditioning System Design. Heating and air-conditioning systems shall be sized, designed, and have their equipment selected in accordance with the following:

(1) Heat loss and heat gain are established in accordance with ACCA Manual J, ASHRAE handbooks, or other equivalent methods.

(2) Duct systems shall be sized in accordance with ACCA Manual D, ASHRAE handbooks, or other equivalent methods.

(3) Heating and cooling equipment in accordance with ACCA Manual S or other equivalent methods.

E 608.0 Low VOC Solvent Cement and Primer.

E 608.1 General. Primers and solvent cements used to join plastic pipe, and fittings shall be in accordance with Section E 608.1.1 and Section E 608.1.2.

E 608.1.1 Solvent Cement. Solvent cement, including one-step solvent cement, shall have a volatile organic compound (VOC) content of less than or equal to 65 ounces per gallon (oz/gal) (487 g/L) for CPVC cement, 68 oz/gal (509 g/L) for PVC cement, and 43 oz/gal (322 g/L) for ABS cement, as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A. E 608.1.2 Primer. Primer shall have a volatile organic compound (VOC) content of less than or equal to 73 oz/gal (546 g/L), as determined by the South Coast Air Quality Management District’s Laboratory Methods of Analysis for Enforcement Samples, Method 316A.

E 701.0 Installer Qualifications.

E 701.1 Scope. The provisions of this section address minimum qualifications of installers of mechanical systems covered within the scope of this appendix.

E 702.0 Qualifications.

E 702.1 General. Where permits are required, the Authority Having Jurisdiction shall have the authority to require contractors, installers, or service technicians to demonstrate competency. Where determined by the Authority Having Jurisdiction, the contractor, installer, or service technician shall be licensed to perform such work.

Part I

CRC § 1974-17 Medium relevance — show source text

Adopting agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting agency	BSC	BSC- CG	SFM	1	2	1/AC	AC	SS	SS/CC	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt entire chapter
Adopt entire chapter as amended (amended sections listed below)			X	X
Adopt only those sections that are listed below
Chapter / Section
AAMA				X
ACCA				X
ANSI			X	X
ASME				X
ASTM			X	X
ASTM E108-2020a			X
CSA				X
DASMA				X
ICC			X	X
IFC-18				X
ISO				X
NFPA			X	X
NFPA 68-13			X
SFM			X
UBC			X
UL				X
UL 790 Edition 9 2022			X
UL 1974-17			X
UL 9540-20			X
UL 9540 Edition 4 2019			X
WDMA				X

The state agency does not adopt sections identified with the following symbol: †

2025 CALIFORNIA RESIDENTIAL CODE 44-1

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

44-2 2025 CALIFORNIA RESIDENTIAL CODE

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

Part IX— Referenced Standards

44 REFERENCED STANDARDS

Notwithstanding California laws and regulations, these referenced standards shall be applicable only to those California Residential Code sections that are adopted.

User notes:

CRC § 905.1 Medium relevance — show source text
905.1 Grade . . . . . . . . . . . . . . . . . . . . . .190

905.2 Horizontal Drainage Pipe . . . . . . .190

905.3 Vent Pipe Rise . . . . . . . . . . . . . . .190

905.4 Roof Termination . . . . . . . . . . . . .190

905.5 Location of Opening . . . . . . . . . . .190

905.6 Common Vertical Pipe . . . . . . . . .190

906.0 Vent Termination . . . . . . . . . . . . .190

906.1 Roof Termination . . . . . . . . . . . . .190

906.2 Clearance . . . . . . . . . . . . . . . . . . .190

906.3 Use of Roof . . . . . . . . . . . . . . . . .190

906.4 Outdoor Installations . . . . . . . . . . .190

906.5 Joints . . . . . . . . . . . . . . . . . . . . . .190

906.6 Lead . . . . . . . . . . . . . . . . . . . . . . .190

906.7 Frost or Snow Closure . . . . . . . . .190

907.0 Vent Stacks and Relief Vents . . . .190

907.1 Drainage Stack . . . . . . . . . . . . . . .190

907.2 Yoke Vent . . . . . . . . . . . . . . . . . . .190

908.0 Wet Venting . . . . . . . . . . . . . . . . .190

908.1 Vertical Wet Venting . . . . . . . . . . .190

908.2 Horizontal Wet Venting for a Bathroom Group . . . . . . . . . . . . . .191

909.0 Special Venting for Island Fixtures . . . . . . . . . . . . . . . . . . . . .191

909.1 General . . . . . . . . . . . . . . . . . . . . .191

910.0 Combination Waste and Vent

Systems . . . . . . . . . . . . . . . . . . . .191

910.1 Where Permitted . . . . . . . . . . . . . .191

910.2 Approval . . . . . . . . . . . . . . . . . . . .191

910.3 Vents . . . . . . . . . . . . . . . . . . . . . .191

910.4 Connections and Size . . . . . . . . .191

910.5 Vertical Waste Pipe . . . . . . . . . . .191

910.6 Cleanouts . . . . . . . . . . . . . . . . . . .191

910.7 Fixtures . . . . . . . . . . . . . . . . . . . . .191

911.0 Circuit Venting . . . . . . . . . . . . . . .191

911.1 Circuit Vent Permitted . . . . . . . . .191

911.2 Circuit Vent Size and

Connection . . . . . . . . . . . . . . . . . .192
CRC § 403.4.5 Medium relevance — show source text
E 403.4.5 Discharge Water to Drain. Where discharge water is not recovered for reuse, the sump overflow line shall not be directly connected to a drain. Where the discharge water is discharged into a sanitary drain, an air gap of not less than 6 inches (152 mm) shall be provided between the termination of the discharge line and the drain opening. The discharge line shall terminate in a location that is visible to the building owner, tenants, or maintenance personnel.

E 403.5 Use of Reclaimed (Recycled) and Onsite Treated Nonpotable Water for Cooling. Where approved for use by the water or wastewater utility and the Authority Having Jurisdiction, reclaimed (recycled), or onsite treated nonpotable water shall be permitted to be used for industrial and commercial cooling or air-conditioning.

E 403.5.1 Drift Eliminator. A drift eliminator shall be utilized in a cooling system, utilizing alternate sources of water, where the aerosolized water is capable of coming in contact with employees or members of the public.

E 403.5.2 Disinfection. A biocide shall be used to treat the cooling system recirculation water where the recycled water is capable of coming in contact with employees or members of the public.

E 501.0 Heating, Ventilation, and Air-Conditioning Systems and Equipment – Energy Efficiency. E 501.1 Scope. The provisions of this section shall establish the means of enhancing energy efficiency associated with mechanical systems in a building.

E 502.0 Heating, Ventilation, and Air-Conditioning Low-Rise Residential Buildings. E 502.1 General. The heating, ventilating, air-conditioning, for single-family houses, multi-family structures not exceeding three stories above grade, and modular houses shall be in accordance with Section E 502.2 through Section E 502.12. The heating, ventilation, and air-conditioning system of other buildings shall be in accordance with Section E 503.0. E 502.2 Heating, Ventilating, and Air-Conditioning Systems and Equipment. This section shall regulate only equipment using single-phase electric power, air conditioners, and heat pumps with rated cooling capacities less than 65 000 British thermal units per hour (Btu/h) (19 kW), warm air furnaces with rated heating capacities less than 225 000 Btu/h (66 kW), boilers less than 300 000 Btu/h (88 kW) input, and heating-only heat pumps with rated heating capacities less than 65 000 Btu/h (19 kW). [ASHRAE 90.2:6.2] E 502.2.1 Nonresidential Type Systems and Equipment. Heating, ventilating, and air-conditioning systems and equipment that do not fall under the requirements of Section E 502.0 shall be in accordance with the applicable requirements of Section E 503.0. E 502.3 Balancing. The air distribution system design, including outlet grilles, shall provide a means for balancing the air distribution system unless the design procedure provides a system intended to operate within plus or minus 10 percent of design air quantities. [ASHRAE 90.2:6.3] E 502.3.1 Balancing Dampers. Balancing dampers shall be installed in branch ducts, and the axis of the damper shall be installed parallel to the direction of airflow in the main duct.
CRC § 206.6 Medium relevance — show source text
11B-206.6, 11B-411 Detectable warnings 1112A.9, 1116A.5, 11B-247, 11B-705 Detention and correctional

facilities 11B-232, 11B-807 Dimensions for adults and

children 11B-102

Dining areas 11B-226, 11B-902 Dining surfaces and work surfaces 11B- 226, 11B-902 Doors, doorways and gates 1126A, 1132A, 11B-206.5, 11B-404 Dressing, fitting and locker rooms 11B- 222, 11B-803 Dressing rooms 11B-222, 11B-803 Drinking fountains 1139A Bottle-filling stations 11B-211, 11B- 602, 11B-602.10 Dwelling units Chapter 11A Egress (see Accessible Means Of Egress) 1009 Electrical Vehicle Charging Stations 406.2.7, 11B-228, 11B-812 Elevators 1009.2.1, 1009.4, 1009.7.3, 1124A, 11B-206.6, 11B-407, 3001.2,

3001.4 Emergency housing Appendix Q Employee work areas 11B-206.2.8, 11B-215.3

Entrances Chapter 11A, 11B-206.4 Equivalent facilitation Chapter 11A

INDEX

Exercise machines and equipment 11B-236, 11B-1004 Existing buildings 1102A.2, 11B- 202 Fire alarm systems 11B-215, 11B-702 Fishing piers and platforms 11B-237, 11B-1005 Floor or ground surfaces 11B-302 General exceptions 11B-203 Golf facilities 11B-238, 11B-1006 Grab bar 1127A, 1134A, 11B-609 Ground floor Chapter 11A Guard (or guardrail) 1114A, 1116A, 1122A, 1125A Handrails 1114A, 1115A, 1122A, 1123A,

11B-505 International symbol of accessibility Chapter 11A, 11B- 703.7.2.1

Judicial facilities 11B-231, 11B-808 Kitchens, kitchenettes and wet bars 1133A, 11B-212 Knee and toe clearance 11B-306

Knee and toe space 1127A, 1133A, 1134A, 1138A Laundry 1127A, 1135A Lifts 1009.5 Limited-use/limited-application elevators 11B-206.6, 11B-408 Live/work unit 508.5.9 Mail boxes 11B-228

Maintenance of accessible
CRC § 502.10.3 Medium relevance — show source text
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

APPENDIX E

E 502.10.3 Humidity Control. Where additional energy-consuming equipment is provided for adding moisture to maintain specific selected relative humidities in spaces or zones, a humidistat shall be provided. This device shall be capable of being set to prevent energy from being used to produce relative humidity within the space above 30 percent. [ASHRAE 90.2-2007:6.10.3.1] E 502.10.3.1 Cooling. Where additional energyconsuming equipment is provided for reducing humidity, it shall be equipped with controls capable of being set to prevent energy from being used to produce a relative humidity within the space below 50 percent during periods of human occupancy and below 60 percent during unoccupied periods.

[ASHRAE 90.2-2007:6.10.3.2] E 502.10.4 Freeze Protection Systems and Snow/Ice Melting. Freeze protection systems, such as heat tracing of outdoor piping and heat exchangers, including self-regulating heat tracing, shall include automatic controls capable of and configured to shut off the systems where outdoor air temperatures are above 40°F (4°C) or where the conditions of the protected fluid will prevent freezing. Snow- and ice-melting systems shall include automatic controls capable of and configured to shut off the systems where the pavement temperature is above 50°F (10°C) and no precipitation is falling and an automatic or manual control that will allow shutoff where the outdoor temperature is above 40°F (4°C) so that the potential for snow or ice accumulation is negligible.

[ASHRAE 90.1:6.4.3.7] E 502.10.5 Other Controls. Where setback, zoned, humidity and cooling controls and equipment are provided, they shall be designed and installed in accordance with Section E 502.10 through Section E 502.10.3.1.

[ASHRAE 90.2-2007:6.10.3.3]

E 502.11 Whole House Fans. Whole house exhaust fans

shall have insulated louvers or covers which close where the

fan is off. Covers or louvers shall have an insulation value of not less than R-4.2, and shall be installed in accordance with the manufacturer’s installation instructions. The attic openings shall be sufficient to accommodate the ventilation capacity of the whole house fan. The operation of the whole house fan shall be considered in determining the adequacy of providing combustion air in accordance with this code. E 502.12 Dampers. Dampers shall be installed to close off outdoor air inlets and exhaust outlets where the ventilation system is not operating.

E 503.0 Heating, Ventilation, and Air-Conditioning – Other than Low-Rise Residential Buildings. E 503.1 General. The heating, ventilation, and air-conditioning in buildings, other than single-family houses, multi-family structures of not more than three stories above grade, and modular houses, shall be in accordance with Section E 503.0.

E 503.1.1 New Buildings. Mechanical equipment and systems serving the heating, cooling, ventilating, or refrigeration needs of new buildings shall comply with the requirements of this section as described in Section E 503.2. [ASHRAE 90.1:6.1.1.1]

Frequently asked questions

How is the required whole‑house ventilation flow (Qtot) computed?

Qtot is computed by the CMC Appendix E formula: Qtot = 0.03 · Afloor + 7.5 · (Nbr + 1) (CFM). See § E 605.1.3.1.

Can I use windows instead of mechanical ventilation?

Not generally in California. The Energy Code requires mechanical ventilation per ASHRAE 62.2 with limited AHJ exceptions; check § 150.0(o) and § E 605.1.3 for the narrow circumstances where window operation may be allowed.

Can infiltration reduce the mechanical ventilation requirement?

Yes — calculate the Effective Annual Average Infiltration Rate (Qinf) from a blower‑door Q50 using § E 605.1.3.2 and subtract it from Qtot to size mechanical ventilation, subject to ASHRAE 62.2 weather/shielding factors.

What must a CFI (central fan integrated) ventilation system include to comply in California?

CFI systems must have motorized outdoor‑air damper(s) that close when ventilation is not required, controls to track run time, and must not use continuous AHU fan operation as the sole method for whole‑house ventilation — per the Energy Code amendments in § 150.0(o).

Where do I find the required sound and measurement procedures for the installed ventilation?

The Energy Code (Section 160.2) requires airflow measurement at the fan inlet/outlet using approved methods and sound rating per ASHRAE 62.2 procedures; see § 160.2 for those test/label rules.

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California Residential Code