Where the CRC points you for Mechanical (HVAC) rules

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

• CRC § 1305.2.6 High relevance — show source text

  TABLE 1305.2.6(2)—CONSTRUCTION-TYPE FACTOR	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10
  FACTOR	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION	TYPE OF CONSTRUCTION
  FACTOR	IA	IB	IIA	IIB	IIIA	IIIB	IV	VA	VB
  	1.2	1.5	2.2	3.5	2.5	3.5	2.3	3.3	7

  1305.2.6.1 Vertical opening formula. The following formula shall be used in computing vertical opening value.

  Equation 13-6 VO = PV × CF

  where:

  VO = Vertical opening value. The calculated value shall not be greater than positive 2.0.

  PV = Protection value from Table 1305.2.6(1).

  CF = Construction-type factor from Table 1305.2.6(2).

  1305.2.7 HVAC systems. Evaluate the ability of the HVAC system to resist the movement of smoke and fire beyond the point of origin. Under the categories in Section 1305.2.7.1, determine the appropriate value and enter that value into Table 1306.1 under Safety Parameter 1305.2.7, HVAC Systems, for fire safety, means of egress and general safety. Facilities in Group I-2 occupancies meeting Category a, b or c shall be considered to fail the evaluation.

  2025 CALIFORNIA EXISTING BUILDING CODE 13-7

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

  PERFORMANCE COMPLIANCE METHODS

  1305.2.7.1 Categories. The categories for HVAC systems are:

  1. Category a—Plenums not in accordance with Section 602 of the International Mechanical Code . -10 points.

  2. Category b—Air movement in egress elements not in accordance with Section 1020.6 of the International Building Code . -5 points.

  3. Category c—Both Categories a and b are applicable. -15 points.

  4. Category d—Compliance of the HVAC system with Section 1020.6 of the International Building Code and Section 602 of the International Mechanical Code . 0 points.

  5. Category e—Systems serving one story; or a central boiler/chiller system without ductwork connecting two or more stories or where systems have no ductwork. +5 points.

• CRC § 1305.2.6 Medium relevance — show source text

  PV = Protection value from Table 1305.2.6(1).

  CF = Construction-type factor from Table 1305.2.6(2).

  1305.2.7 HVAC systems. Evaluate the ability of the HVAC system to resist the movement of smoke and fire beyond the point of origin. Under the categories in Section 1305.2.7.1, determine the appropriate value and enter that value into Table 1306.1 under Safety Parameter 1305.2.7, HVAC Systems, for fire safety, means of egress and general safety. Facilities in Group I-2 occupancies meeting Category a, b or c shall be considered to fail the evaluation.

  2025 CALIFORNIA EXISTING BUILDING CODE 13-7

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

  PERFORMANCE COMPLIANCE METHODS

  1305.2.7.1 Categories. The categories for HVAC systems are:

  1. Category a—Plenums not in accordance with Section 602 of the International Mechanical Code . -10 points.

  2. Category b—Air movement in egress elements not in accordance with Section 1020.6 of the International Building Code . -5 points.

  3. Category c—Both Categories a and b are applicable. -15 points.

  4. Category d—Compliance of the HVAC system with Section 1020.6 of the International Building Code and Section 602 of the International Mechanical Code . 0 points.

  5. Category e—Systems serving one story; or a central boiler/chiller system without ductwork connecting two or more stories or where systems have no ductwork. +5 points.

  1305.2.8 Automatic fire detection. Evaluate the smoke detection capability based on the location and operation of automatic fire detectors in accordance with the International Mechanical Code and Section 907 of the International Building Code. Under the categories and occupancies in Table 1305.2.8, determine the appropriate value and enter that value into Table 1306.1 under Safety Parameter 1305.2.8, Automatic Fire Detection, for fire safety, means of egress and general safety. Facilities in Group I-2 occupancies meeting Category a, b or c shall be considered to fail the evaluation.

• CRC § 503.4.6.3.1. Medium relevance — show source text

  Each isolation area shall be controlled independently by a device meeting the requirements of Section E 503.4.6.3.1. For central systems and plants, controls and devices shall be provided to allow stable system and equipment operation for any length of time while serving only the smallest isolation area served by the system or plant.

  Exceptions: Isolation devices and controls are not required for the following:

  (1) Exhaust air and outdoor air connections to isolation zones where the fan system to which they connect is not more than 5000 ft [3] /min (2.3597 m [3] /s).

  (2) Exhaust airflow from a single isolation zone of less than 10 percent of the design airflow of the exhaust system to which it

  connects.

  (3) Zones intended to operate continuously or intended to be inoperative only when all other zones are inoperative. [ASHRAE 90.1:6.4.3.3.4]

  2025 CALIFORNIA MECHANICAL CODE 423

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

  APPENDIX E

  E 503.4.6.3.5 Automatic Control of HVAC in Hotel/Motel Guest Rooms. Hotels and motels with more than 50 guest rooms shall be provided with automatic controls for the HVAC equipment serving each guest room capable of and configured according to the requirements in Section E 503.4.6.3.5.1. [ASHRAE 90.1:6.4.3.3.5]

  E 503.4.6.3.5.1 Guest Room HVAC Set-Point Control. Within 30 minutes of all occupants leaving the guest room, HVAC set points shall be automatically raised by not less than 4°F (2°C) from the occupant set point in the cooling mode and automatically lowered by at least 4°F (2°C) from the occupant set point in the heating mode. When the guest room is unrented and unoccupied, HVAC set points shall be automatically reset to 80°F (27°C) or higher in the cooling mode and to 60°F (16°C) or lower in the heating mode. Unrented and unoccupied guest rooms shall be determined by either of the following:

  (1) The guest room has been continuously unoccupied for up to 16 hours.

  (2) A networked guest room control system indicates the guest room is unrented and the guest room is unoccupied for no more than 30 minutes.

  Exceptions:

  (1) A networked guest room control system shall be permitted to return the thermostat set points to their default occupied set points 60 minutes prior to the time the room is scheduled to be occupied.

  (2) Cooling for humidity control shall be permitted during unoccupied periods.

  E 503.4.6.4 Stair and Elevator Shaft Vent Dampers. Where stair and elevator shafts have vents, they shall be equipped with motorized dampers that are capable of and configured to automatically close during normal building operation and are interlocked to only open as required by fire and smoke detection systems, or by thermostatic control systems.

• CRC § 2025 Medium relevance — show source text

  It is important to understand that the IRC contains coverage for what is conventional and common in residential construction practice. While the IRC will provide all of the needed coverage for most residential construction, it might not address construction practices and systems that are atypical or rarely encountered in the industry. Therefore, the IRC contains several references to other codes either as an alternative to the provisions of the IRC or where the IRC lacks coverage for a particular type of structure, design, system, appliance or method of construction. In other words, the IRC is meant to be all inclusive for typical residential construction and it relies on other codes only where alternatives are desired or where the code lacks coverage for the uncommon aspect of residential construction. Of course, the IRC constantly evolves to address new technologies and construction practices that were once uncommon, but are now common.

  The IRC is unique in that much of it, including Chapters 3 through 9 and Chapters 34 through 43, is presented in an ordered format that is consistent with the normal progression of construction, starting with the design phase and continuing through the final trimout phase. This is consistent with the “cookbook” philosophy of the IRC.

  2025 CALIFORNIA RESIDENTIAL CODE xiii

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

  xiv 2025 CALIFORNIA RESIDENTIAL CODE

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

  Arrangement and Format of the 2025 CRC

  The CRC is divided into nine main parts, specifically: Part I—Administrative, Part II—Definitions, Part III—Building Planning and Construction, Part IV—Energy Conservation, Part V—Mechanical, Part VI—Fuel Gas, Part VII—Plumbing, Part VIII—Electrical and Part IX—Referenced Standards. Parts IV through VIII of IRC are not adopted in California and replaced with references to appropriate parts of Title 24. The following provides a brief description of the content of each chapter and appendix of the CRC:

  Chapter 1 Scope and Administration.

  Chapter 1 establishes the limits of applicability of the code and describes how the code is to be applied and enforced. The provisions of Chapter 1 establish the authority and duties of the code official appointed by the authority having jurisdiction and also establish the rights and privileges of the design professional, contractor and property owner.

  Chapter 2 Definitions.

  Chapter 2 is the repository of the definitions of terms used in the body of the code. The user of the code should be familiar with and consult this chapter because the definitions are essential to the correct interpretation of the code and because the user may not be aware that a term is defined.

  Chapter 3 Building Planning.

  Chapter 3 provides guidelines for a minimum level of structural integrity, life safety, fire safety and livability for inhabitants of dwelling units regulated by this code. Chapter 3 is a compilation of the code requirements specific to the building planning sector of the design and construction process. This chapter sets forth code requirements dealing with light, ventilation, sanitation, minimum room size, ceiling height and environmental comfort. Chapter 3 establishes life-safety provisions including limitations on glazing used in hazardous areas, specifications on stairways, use of guards at elevated surfaces, window and fall protection, and rules for means of egress. Snow, wind and seismic design live and dead loads and flood-resistant construction, as well as solar energy systems are addressed in this chapter.

  Chapter 4 Foundations.

• CRC § 503.4.6.3.5.1 Medium relevance — show source text

  E 503.4.6.3.5.1 Guest Room HVAC Set-Point Control. Within 30 minutes of all occupants leaving the guest room, HVAC set points shall be automatically raised by not less than 4°F (2°C) from the occupant set point in the cooling mode and automatically lowered by at least 4°F (2°C) from the occupant set point in the heating mode. When the guest room is unrented and unoccupied, HVAC set points shall be automatically reset to 80°F (27°C) or higher in the cooling mode and to 60°F (16°C) or lower in the heating mode. Unrented and unoccupied guest rooms shall be determined by either of the following:

  (1) The guest room has been continuously unoccupied for up to 16 hours.

  (2) A networked guest room control system indicates the guest room is unrented and the guest room is unoccupied for no more than 30 minutes.

  Exceptions:

  (1) A networked guest room control system shall be permitted to return the thermostat set points to their default occupied set points 60 minutes prior to the time the room is scheduled to be occupied.

  (2) Cooling for humidity control shall be permitted during unoccupied periods.

  E 503.4.6.4 Stair and Elevator Shaft Vent Dampers. Where stair and elevator shafts have vents, they shall be equipped with motorized dampers that are capable of and configured to automatically close during normal building operation and are interlocked to only open as required by fire and smoke detection systems, or by thermostatic control systems.

  Exception: Nonmotorized gravity back draft dampers are acceptable in buildings less than three stories in height and for buildings of any height located in Climate Zones 0, 1, 2, and 3. [ASHRAE 90.1:6.4.3.4.1]

  E 503.4.6.4.1 Shutoff Damper Controls. Outdoor air intake and exhaust systems shall be equipped with motorized dampers that will automatically shut when the systems or spaces served are not in use. Outdoor air and exhaust or relief dampers shall be capable of and configured to automatically shut off during preoccupancy building warm-up, cooldown, and setback, except when the supply of outdoor air reduces energy costs or when outdoor air shall

  be supplied to comply with the code require ments.

  Exceptions:

  (1) Nonmotorized (gravity back draft) dampers shall be permitted for exhaust and relief in buildings less than three stories in height and for outdoor air intakes and exhaust and relief dampers in buildings of any height located in Climate Zones 0, 1, 2 and 3. Nonmotorized dampers for outdoor air intakes shall be protected from direct exposure to wind.

  (2) Nonmotorized dampers shall be permitted in systems with a design outdoor air intake or exhaust capacity of 300 ft [3] /min (0.142 m [3] /s) or less.

  (3) Dampers shall not be required in ventilation or exhaust systems serving unconditioned spaces.

  (4) Dampers shall not be required in exhaust systems serving Type 1 kitchen exhaust hoods.

  (5) Dampers are not required in systems intended to operate continuously. [ASHRAE 90.1:6.4.3.4.2]

• CRC § 13-7 Medium relevance — show source text

  2025 CALIFORNIA EXISTING BUILDING CODE 13-7

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

  PERFORMANCE COMPLIANCE METHODS

  1305.2.7.1 Categories. The categories for HVAC systems are:

  1. Category a—Plenums not in accordance with Section 602 of the International Mechanical Code . -10 points.

  2. Category b—Air movement in egress elements not in accordance with Section 1020.6 of the International Building Code . -5 points.

  3. Category c—Both Categories a and b are applicable. -15 points.

  4. Category d—Compliance of the HVAC system with Section 1020.6 of the International Building Code and Section 602 of the International Mechanical Code . 0 points.

  5. Category e—Systems serving one story; or a central boiler/chiller system without ductwork connecting two or more stories or where systems have no ductwork. +5 points.

  1305.2.8 Automatic fire detection. Evaluate the smoke detection capability based on the location and operation of automatic fire detectors in accordance with the International Mechanical Code and Section 907 of the International Building Code. Under the categories and occupancies in Table 1305.2.8, determine the appropriate value and enter that value into Table 1306.1 under Safety Parameter 1305.2.8, Automatic Fire Detection, for fire safety, means of egress and general safety. Facilities in Group I-2 occupancies meeting Category a, b or c shall be considered to fail the evaluation.

  TABLE 1305.2.8—AUTOMATIC FIRE DETECTION VALUES	Col2	Col3	Col4	Col5	Col6	Col7
  OCCUPANCY	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES
  OCCUPANCY	a	b	c	d	e	f
  A-1, A-3, F, M, R, S-1	-10	-5	0	2	6	NA
  A-2	-25	-5	0	5	9	NA
  A-4, B, E, S-2	-4	-2	0	4	8	NA
  I-2	NP	NP	NP	4	5	2
  NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.

  1305.2.8.1 Categories. The categories for automatic fire detection are:

• California Residential Code Medium relevance — show source text

  
  2
  3|120
  123
  126|444
  498
  540|216
  247
  281|142
  145
  147|582
  652
  705|277
  321
  366|165
  168
  171|739
  825
  893|348
  407
  463| |15|1
  2
  3|125
  128
  131|511
  558
  597|229
  260
  292|153
  156
  159|658
  718
  760|297
  339
  382|184
  187
  190|824
  900
  960|375
  432
  486| |20|1
  2
  3|123
  126
  129|584
  625
  661|239
  270
  301|150
  153
  156|752
  805
  851|312
  354
  396|180
  184
  187|943
  1011
  1067|397
  452
  505| |30|1
  2
  3|119
  122
  125|680
  715
  746|255
  287
  317|145
  149
  152|883
  928
  968|337
  378
  418|175
  179
  182|1115
  1171
  1220|432
  484
  535| |50|1
  2
  3|115
  118
  121|798
  827
  854|294
  326
  357|140
  143
  147|1049
  1085
  1118|392
  433
  474|168
  172
  176|1334
  1379
  1421|506
  558
  611| |100|1
  2
  3|109
  113
  116|907
  933
  956|334
  368
  399|134
  138
  141|1222
  1253
  1282|454
  497
  540|161
  165
  169|1589
  1626
  1661|596
  651
  705|

  Col1	COMMON VENT CAPACITY	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10
  	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)	MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)
  	63	63	63	78	78	78	113	113	113
  	**COMBINED APPLIANCE INPUT RATING

• CRC § 90.1 Medium relevance — show source text

  (3) Variable flow is not required for primary pumps in a primary/secondary system.

  (4) Variable flow is not required for a coil pump provided for freeze protection.

  (5) Variable flow is not required for heat recovery coil runaround loops. [ASHRAE 90.1:6.5.4.2]

  CHILLED WATER PUMPS IN THESE CLIMATE ZONES	HEATING WATER PUMPS IN THESE CLIMATE ZONES	MOTOR NAMEPLATE HORSEPOWER
  0A, 0B, 1A, 1B, 2B	NR	≥2 hp
  2A, 3B	NR	≥3 hp
  3A, 3C, 4A, 4B	7, 8	≥5 hp
  4C, 5A, 5B, 5C, 6A, 6B	3C, 5A, 5C, 6A, 6B	≥7.5 hp
  ─	4A, 4C, 5B	≥10 hp
  7, 8	4B	≥15 hp
  ─	2A, 2B, 3A, 3B	≥25 hp
  ─	1B	≥100 hp
  ─	0A, 0B, 1A	≥200 hp

  For SI units: 1 horsepower = 0.746 kW

  E 503.5.7.3 Chiller and Boiler Isolation. Where a chilled-water plant includes more than one chiller, provisions shall be made so that the fluid flow through the chiller is automatically shut off where the chiller is shut down. Chillers piped in series for the purpose of increased temperature differential, shall be considered as one chiller. Where constant-speed chilled-water or condenser water pumps are used to serve multiple chillers, the number of pumps shall be not less than the number of chillers and staged on and off with the chillers. [ASHRAE 90.1:6.5.4.3.1]

  E 503.5.7.3.1 Boiler Isolation. Where a boiler plant includes more than one boiler, provisions shall be made so that the flow through the boiler is automatically shut off where the boiler is shut down. Where constant-speed hot-water pumps are used to serve multiple boilers, the number of pumps shall be not less than the number of boilers and staged on and off with the boilers.

  [ASHRAE 90.1:6.5.4.3.2]

  E 503.5.7.4 Chilled- and Hot-Water Tempera- ture Reset Controls. Chilled- and hot-water systems with a design capacity exceeding 300 000 Btu/h (88 kW) supplying chilled or heated water to comfort conditioning systems shall include controls that automatically reset supply water temperatures by representative building loads (including return water temperature) or by outdoor air temperature. Where DDC is used to control valves, the set point shall be reset based on valve positions until one valve is nearly wide open or setpoint limits of the system equipment or application have been reached.

  Exceptions:

• CRC § 101.5 Medium relevance — show source text

  101.5 Validity. Where a provision of this code, or the application thereof to a person or circumstance, is held invalid, the remainder of the code, or the application of such provision to other persons or circumstances, shall not be affected thereby.

  102.0 Applicability. 102.1 Conflicts Between Codes. Where the requirements within the jurisdiction of this mechanical code conflict with the requirements of the plumbing code, the plumbing code shall prevail. In instances where this code, applicable standards, or the manufacturer’s installation instructions conflict, the more stringent provisions shall prevail. Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall prevail. [OSHPD 1, 1R, 2, 3, 4 & 5] See Chapter 1, Division I, Section 1.1.7

  102.2 Existing Installations. Mechanical systems lawfully in existence at the time of the adoption of this code shall be permitted to have their use, maintenance, or repair continued where the use, maintenance, or repair is in accordance with the original design and location and no hazard to life, health, or property has been created by such mechanical system.

  102.3 Maintenance. Mechanical systems, materials, and appurtenances, both existing and new, of a premise under the Authority Having Jurisdiction shall be maintained in operating condition. Devices or safeguards required by this code shall be maintained in accordance with the code edition under

  which installed.

  The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a mechanical system to be reinspected.

  102.3.1 Commercial HVAC Systems. Commercial HVAC systems both existing and new, and parts thereof shall be inspected and maintained in operating condition in accordance with ASHRAE/ACCA 180. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected. 102.3.2 Residential HVAC Systems. Residential HVAC systems both existing and new, and parts thereof shall be inspected in accordance with ACCA 4 QM. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected.

  102.4 Additions, Alterations, Renovations, or Repairs. Additions, alterations, renovations, or repairs shall conform to that required for a new system without requiring the existing mechanical system to be in accordance with the requirements of this code. Additions, alterations, renovations, or repairs shall not cause an existing system to become unsafe, insanitary or overloaded.

  Additions, alterations, renovations, or repairs to existing mechanical system installations shall comply with the provisions for new construction, unless such deviations are found to be necessary and are first approved by the Authority Having Jurisdiction. 102.5 Health and Safety. Where compliance with the provisions of this code fails to eliminate or alleviate a nuisance, or other dangerous or insanitary condition that involves health or safety hazards, the owner or the owner’s agent shall install such additional mechanical system facilities or shall make such repairs or alterations as ordered by the Authority Having Jurisdiction. **102.6 Changes in Building Occupancy.

• CRC § 102.3.2 Medium relevance — show source text

  ** Commercial HVAC systems both existing and new, and parts thereof shall be inspected and maintained in operating condition in accordance with ASHRAE/ACCA 180. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected. 102.3.2 Residential HVAC Systems. Residential HVAC systems both existing and new, and parts thereof shall be inspected in accordance with ACCA 4 QM. The owner or the owner’s designated agent shall be responsible for maintenance of mechanical systems and equipment. To determine compliance with this subsection, the Authority Having Jurisdiction shall be permitted to cause a HVAC system to be reinspected.

  102.4 Additions, Alterations, Renovations, or Repairs. Additions, alterations, renovations, or repairs shall conform to that required for a new system without requiring the existing mechanical system to be in accordance with the requirements of this code. Additions, alterations, renovations, or repairs shall not cause an existing system to become unsafe, insanitary or overloaded.

  Additions, alterations, renovations, or repairs to existing mechanical system installations shall comply with the provisions for new construction, unless such deviations are found to be necessary and are first approved by the Authority Having Jurisdiction. 102.5 Health and Safety. Where compliance with the provisions of this code fails to eliminate or alleviate a nuisance, or other dangerous or insanitary condition that involves health or safety hazards, the owner or the owner’s agent shall install such additional mechanical system facilities or shall make such repairs or alterations as ordered by the Authority Having Jurisdiction. 102.6 Changes in Building Occupancy. Mechanical systems that are a part of a building or structure undergoing a change in use or occupancy, as defined in the building code, shall be in accordance with the requirements of this code that are applicable to the new use or occupancy. 102.7 Moved Structures. Parts of the mechanical system of a building and part thereof that is moved from one foundation to another, or from one location to another, shall be in accordance with the provisions of this code for new installations and completely tested as prescribed elsewhere in this section for new work, except that walls or floors need not be removed during such test where equivalent means of inspection acceptable to the Authority Having Jurisdiction are provided. 102.8 Appendices. The provisions in the appendices are intended to supplement the requirements of this code and shall not be considered part of this code unless formally adopted as such.

  2025 CALIFORNIA MECHANICAL CODE 21

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

  DIVISION II SCOPE AND ADMINISTRATION

  103.0 Duties and Powers of the Authority Having Jurisdiction.

  103.1 General. The Authority Having Jurisdiction shall be the Authority duly appointed to enforce this code. For such purposes, the Authority Having Jurisdiction shall have the powers of a law enforcement officer. The Authority Having Jurisdiction shall have the power to render interpretations of this code and to adopt and enforce rules and regulations supplemental to this code as deemed necessary in order to clarify the application of the provisions of this code. Such interpretations, rules, and regulations shall comply with the intent and purpose of this code.

• CRC § 1305.2.8 Medium relevance — show source text

  TABLE 1305.2.8—AUTOMATIC FIRE DETECTION VALUES	Col2	Col3	Col4	Col5	Col6	Col7
  OCCUPANCY	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES
  OCCUPANCY	a	b	c	d	e	f
  A-1, A-3, F, M, R, S-1	-10	-5	0	2	6	NA
  A-2	-25	-5	0	5	9	NA
  A-4, B, E, S-2	-4	-2	0	4	8	NA
  I-2	NP	NP	NP	4	5	2
  NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.	NA = Not Applicable. NP = Not Permitted.

  1305.2.8.1 Categories. The categories for automatic fire detection are:

  1. Category a—None.
  2. Category b—Existing smoke detectors in HVAC systems and maintained in accordance with the International Fire Code .
  3. Category c—Smoke detectors in HVAC systems. The detectors are installed in accordance with the requirements for new buildings in the International Mechanical Code .
  4. Category d—Smoke detectors throughout all floor areas other than individual sleeping units, tenant spaces and dwelling units.
  5. Category e—Smoke detectors installed throughout the floor area.
  6. Category f—Smoke detectors in corridors only.

  1305.2.9 Fire alarm systems. Evaluate the capability of the fire alarm system in accordance with Section 907 of the International Building Code . Under the categories and occupancies in Table 1305.2.9, determine the appropriate value and enter that value into Table 1306.1 under Safety Parameter 1305.2.9, Fire Alarm System, for fire safety, means of egress and general safety.

  TABLE 1305.2.9—FIRE ALARM SYSTEM VALUES	Col2	Col3	Col4	Col5
  OCCUPANCY	CATEGORIES	CATEGORIES	CATEGORIES	CATEGORIES
  OCCUPANCY	a	ba	c	d
  A-1, A-2, A-3, A-4, B, E, R	-10	-5	0	5
  F, M, S	0	5	10	15
  I-2	-4	1	2	5
  a. For buildings equipped throughout with an automatic sprinkler system, add 2 points for activation by a sprinkler water-flow device.	a. For buildings equipped throughout with an automatic sprinkler system, add 2 points for activation by a sprinkler water-flow device.	a. For buildings equipped throughout with an automatic sprinkler system, add 2 points for activation by a sprinkler water-flow device.	a.

• CRC § 150.2 Medium relevance — show source text

  Exception 3 to Section 150.2(a): Space-conditioning system. When heating or cooling will be extended to an addition from the existing system(s), the existing heating and cooling equipment need not comply with Part 6. The heating system capacity must be adequate to meet the minimum requirements of CRC 303.10.

  Exception 4 to Section 150.2(a): Space-conditioning system ducts. When any length of duct is extended from an existing duct system to serve the addition, the existing duct system and the extended duct shall meet the applicable requirements specified in Section 150.2(b)1Di and 150.2(b)1Dii.

  Exception 5 to Section 150.2(a): Additions 1,000 square feet or less are not required to comply with the ventilation cooling requirements of Section 150.1(c)12.

  Exception 6 to Section 150.2(a): Photovoltaic systems, as specified in Section 150.1(c)14, are not required for additions.

  1. Prescriptive approach. Additions to existing buildings shall meet the following additional requirements: A. Additions that are greater than 700 square feet shall meet the requirements of Section 150.1(c), with the following modifications:

  i. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing. ii. The maximum allowed fenestration area shall be the greater of 175 square feet or 20 percent of the addition floor area, and the maximum allowed west-facing fenestration area shall be the greater of 70 square feet or the requirements of Section 150.1(c).

  iii. Alterations that add fenestration area shall have a maximum SHGC value of 0.23 in Climate Zone 15.

  iv. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing shall be installed and continuous insulation is not required. v. Additions that consist of the conversion of existing spaces from unconditioned to conditioned space shall not be required to perform the following as part of QII: a. Existing window and door headers shall not be required to be insulated. b. Air sealing shall not be required when the existing air barrier is not being removed or replaced. B. Additions that are 700 square feet or less shall meet the requirements of Section 150.1(c), with the following modifications: i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater. b. In Climate Zones 3, and 5 through 7, achieve an overall assembly U -factor not exceeding 0.031. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R value of R-30 or greater.

  ii. Radiant barriers shall be installed in Climate Zones 2-15.

  iii.