How must heating and air‑conditioning systems be sized and selected?

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

• CALGreen § 4.507.1 High relevance — show source text

  4.507.1 Reserved.

  2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 4-17

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

  RESIDENTIAL MANDATORY MEASURES

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

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

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

  SECTION 4.508—OUTDOOR AIR QUALITY (RESERVED)

  4-18 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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

  CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE

  CHAPTER 5 – NONRESIDENTIAL MANDATORY MEASURES

  DIVISION 5.1 – PLANNING AND DESIGN

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

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

• CALGreen § 506.1 High relevance — show source text

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

• CALGreen § 4.506 High relevance — show source text

  3. At least three random moisture readings shall be performed on wall and floor framing with documentation acceptable to the enforcing agency provided at the time of approval to enclose the wall and floor framing.

  Insulation products which are visibly wet or have a high moisture content shall be replaced or allowed to dry prior to enclosure in wall or floor cavities. Wet-applied insulation products shall follow the manufacturers’ drying recommendations prior to enclosure.

  SECTION 4.506—INDOOR AIR QUALITY AND EXHAUST

  4.506.1 Bathroom exhaust fans. Each bathroom shall be mechanically ventilated and shall comply with the following:

  1. Fans shall be ENERGY STAR compliant and be ducted to terminate outside the building.
  2. Unless functioning as a component of a whole house ventilation system, fans must be controlled by a humidity control. a. Humidity controls shall be capable of adjustment between a relative humidity range of ≤ 50 percent to a maximum of 80 percent. A humidity control may utilize manual or automatic means of adjustment. b. A humidity control may be a separate component to the exhaust fan and is not required to be integral (i.e., built-in).

  Notes:

  1. For the purposes of this section, a bathroom is a room which contains a bathtub, shower or tub/shower combination.
  2. Lighting integral to bathroom exhaust fans shall comply with the California Energy Code.

  SECTION 4.507—ENVIRONMENTAL COMFORT

  4.507.1 Reserved.

  2025 CALIFORNIA GREEN BUILDING STANDARDS CODE 4-17

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

  RESIDENTIAL MANDATORY MEASURES

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

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

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

  SECTION 4.508—OUTDOOR AIR QUALITY (RESERVED)

  4-18 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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

  CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE

  CHAPTER 5 – NONRESIDENTIAL MANDATORY MEASURES

  DIVISION 5.1 – PLANNING AND DESIGN

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

• CALGreen § 504.2 High relevance — show source text

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

• CALGreen § 62.2 High 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

• CALGreen § 150.0 High relevance — show source text

  2. In Climate Zones 14 and 16, a Class I or Class II vapor retarder shall be installed on the conditioned space side of all insulation in all exterior walls, vented attics and unvented attics with air-permeable insulation.

  (h) Space-conditioning equipment.

  1. Building cooling and heating loads. Building heating and cooling loads shall be determined using a method based on any one of the following: A. The ASHRAE Handbook, Equipment Volume, Applications Volume and Fundamentals Volume; or B. The SMACNA Residential Comfort System Installation Standards Manual; or

  C. The ACCA Manual J.

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

  iii. The ACCA Manual J.

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

  D. The outdoor design temperatures for cooling shall be no greater than the 1.0 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.

  3. Outdoor condensing units. A. Clearances. Installed air conditioner and heat pump outdoor condensing units shall have a clearance of at least five (5) feet (1.5 meters) from the outlet of any dryer vent. B. Liquid line drier. Installed air conditioner and heat pump systems shall be equipped with liquid line filter driers if required, as specified by manufacturer’s instructions.
  4. 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.
  5. System selection. A. Equipment sizing and selection shall meet the cooling and heating loads of Sections 150.0(h)1 and 2. B. Systems shall be sized based on ACCA Manual S-2023 in accordance with these requirements: i. Cooling capacity: There is no limit on the minimum capacity. ii. Furnaces: Heating capacity shall be sized based on ACCA Manual S-2023, Table N2.5.

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  SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

  iii. Heat pump heating capacity: a. Minimum: Heating systems are required to have a heating capacity meeting the minimum requirements of the CBC, not including any supplementary heating. b. Maximum: There is no limit on the maximum heating capacity.

  6. Defrost.
• CALGreen § 1.0 High relevance — show source text

  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.

  3. Outdoor condensing units. A. Clearances. Installed air conditioner and heat pump outdoor condensing units shall have a clearance of at least five (5) feet (1.5 meters) from the outlet of any dryer vent. B. Liquid line drier. Installed air conditioner and heat pump systems shall be equipped with liquid line filter driers if required, as specified by manufacturer’s instructions.
  4. 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.
  5. System selection. A. Equipment sizing and selection shall meet the cooling and heating loads of Sections 150.0(h)1 and 2. B. Systems shall be sized based on ACCA Manual S-2023 in accordance with these requirements: i. Cooling capacity: There is no limit on the minimum capacity. ii. Furnaces: Heating capacity shall be sized based on ACCA Manual S-2023, Table N2.5.

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  SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

  iii. Heat pump heating capacity: a. Minimum: Heating systems are required to have a heating capacity meeting the minimum requirements of the CBC, not including any supplementary heating. b. Maximum: There is no limit on the maximum heating capacity.

  6. Defrost.

  A. If a heat pump is equipped with an installer adjustable defrost delay timer, the delay timer shall be set to greater than or equal to 90 minutes. B. The installer shall certify on the Certificate of Installation (CF2R) that the control configuration has been tested in accordance with the testing procedure in the CF2R.

  Exception 1 to Section 150.0(h)6. Dwelling units in Climate Zones 6 and 7.

  Exception 2 to Section 150.0(h)6. Dwelling units with a conditioned floor area of 500 square feet or less in Climate Zones 3, 5 through 10, and 15. 7. Supplementary heating control configuration. Heat pumps with supplementary heat, including, but not limited to, electric resistance heaters or gas furnace supplementary heating, shall comply with the following requirements: A. Lock out supplementary heating above an outdoor air temperature of not greater than 35°F. There are additional thermostat requirements in section 150.0(i)2. B. The installer shall certify on the Certificate of Installation that the control configuration has been tested in accordance with the testing procedure found in the CF2R. C. The controls may allow supplementary heater operation above 35°F only during defrost or when the user selects emergency operation.

  Exception 1 to Section 150.0(h)7: For buildings with a conditioned floor area less than 500 square feet, and for buildings of any size in Climate Zones 7 and 15, heat pumps with supplementary heaters shall have controls that meet Item i or ii:

  i. Option A:

  1. That prevent supplementary heater operation when the heating load can be met by the heat pump alone; and
• CALGreen § 25218.5 High relevance — show source text

  For exterior light shelves, the vertical distance between the projected edge of the light shelf and sill of the vertical fenestration below it.

  D = Distance between the existing structure or nature object and the fenestration.

  H AS = Height difference between the top of the existing structure or nature object and the bottom of the fenestration.

  Note: The base edge is the edge of an overhang, slat or light shelf that is adjacent to the vertical fenestration. The projected edge is the opposite edge from the base edge.

  Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8, and 25943, Public Resources Code.

  SECTION 140.4—PRESCRIPTIVE REQUIREMENTS FOR SPACE-CONDITIONING SYSTEMS

  A building complies with this section by being designed with and having constructed and installed a space-conditioning system that meets the applicable prescriptive requirements of Subsections (a) through (q).

  (a) Sizing, equipment selection and type.

  1. Sizing and equipment selection. Mechanical heating and mechanical cooling equipment serving healthcare facilities shall be sized to meet the design heating and cooling loads as calculated according to the Subsection (b). Mechanical heating and mechanical cooling equipment serving hotel/motel buildings and nonresidential buildings other than healthcare facilities shall be the smallest size, within the available options of the desired equipment line, necessary to meet the design heating and cooling loads of the building, as calculated according to Subsection (b). Exception 1 to Section 140.4(a)1: Where it can be demonstrated to the satisfaction of the enforcing agency that oversizing will not increase building LSC. Exception 2 to Section 140.4(a)1: Standby equipment with controls that allow the standby equipment to operate only when the primary equipment is not operating. Exception 3 to Section 140.4(a)1: Multiple units of the same equipment type, such as multiple chillers and boilers, having combined capacities exceeding the design load, if they have controls that sequence or otherwise optimally control the operation of each unit based on load.

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  NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

  COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

  2. Single zone space-conditioning system type. Single zone space-conditioning systems with direct expansion cooling with rated cooling capacity 240,000 Btu/hr or less serving the following spaces shall meet the applicable requirements in Items A–H, or shall meet the performance compliance requirements of Section 140.1. A. Retail and grocery building spaces in Climate Zones 2 through 15. The space-conditioning system shall be a heat pump. B. Retail and grocery building spaces in Climate Zones 1 and 16 with cooling capacity less than 65,000 Btu/hr. The spaceconditioning system shall be an air conditioner with furnace. C. Retail and grocery building spaces in Climate Zones 1 and 16 with cooling capacity 65,000 Btu/hr or greater. The space-conditioning system shall be a dual-fuel heat pump. D. School building spaces.
• CALGreen § 170.2 High relevance — show source text

  5. All skylights shall have a glazing material or diffuser that has a measured haze value greater than 90 percent, tested according to ASTM D1003 (notwithstanding its scope) or another test method approved by the Commission. Exception 1 to Section 170.2(b): In buildings with unfinished interiors, future enclosed spaces for which there are plans to have:

  A. A floor area of less than or equal to 5,000 square feet; or B. Ceiling heights of less than or equal to 15 feet. This exception shall not be used for S-1 or S-2 (storage), or for F-1 or F2 (factory) occupancies. Exception 2 to Section 170.2(b): Enclosed spaces having a designed general lighting system with a lighting power density less than 0.5 watts per square foot. Exception 3 to Section 170.2(b): Enclosed spaces where it is documented that permanent architectural features of the building, existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed space for more than 1500 daytime hours per year between 8 a.m. and 4 p.m.

  (c) Space-conditioning systems. All space heating, space cooling and ventilation equipment shall comply with minimum Appliance Efficiency Regulations as specified in Sections 110.0 through 110.2 and the applicable requirements of Subsections 1 through 4.

  1. Sizing and equipment selection—common use areas. Mechanical heating and mechanical cooling equipment serving common use areas of multifamily buildings shall be the smallest size, within the available options of the desired equipment line, necessary to meet the design heating and cooling loads of the building, as calculated according to Subsection 2 below. Exception 1 to Section 170.2(c)1: Where it can be demonstrated to the satisfaction of the enforcing agency that oversizing will not increase building LSC energy use. Exception 2 to Section 170.2(c)1: Standby equipment with controls that allow the standby equipment to operate only when the primary equipment is not operating. Exception 3 to Section 170.2(c)1: Multiple units of the same equipment type, such as multiple chillers and boilers, having combined capacities exceeding the design load, if they have controls that sequence or otherwise optimally control the operation of each unit based on load.
  2. Calculations—common use areas. In making equipment sizing calculations under Subsection (c)1, all of the following rules shall apply: A. Heating and cooling loads. Heating and cooling system design loads shall be determined in accordance with the method in the 2021 ASHRAE Handbook, Fundamentals Volume, or as specified in a method approved by the Commission.

  B. Indoor design conditions. Indoor design temperature and humidity conditions for comfort applications shall be determined using ASHRAE Standard 55 or the 2021 ASHRAE Handbook, Fundamentals Volume, except that winter humidification and summer dehumidification shall not be required. C. Outdoor design conditions. Outdoor design conditions shall be selected from Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X or the ASHRAE Handbook, Fundamentals Volume. Heating design temperatures shall be no lower than the 99.0 percent Heating Dry Bulb or the Heating Winter Median of Extremes values. Cooling design temperatures shall be no greater than the 0.5 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.

• CALGreen § 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.

  2. Design conditions . Design conditions shall be determined in accordance with the following: A. For the purpose of sizing the space-conditioning (HVAC) system, the indoor design temperatures shall be 68°F for heating and 75°F for cooling. B. Outdoor design conditions shall be selected from one of the following: i. Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X; or ii. The ASHRAE Handbook Fundamentals Volume; or

  iii. The ACCA Manual J.

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

  D. The outdoor design temperatures for cooling shall be no greater than the 1.0 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.

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  MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

  3. 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.
  4. 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.
  5. 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

• CALGreen § 160.3 High relevance — show source text

  e. Excess outdoor air.

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

  (b) Dwelling unit space-conditioning and air distribution systems.

  1. Building cooling and heating loads. Building heating and cooling loads shall be determined using a method based on any one of the following, using cooling and heating loads as two of the criteria for equipment sizing and selection: A. The ASHRAE Handbook, Equipment Volume, Applications Volume and Fundamentals Volume; or B. The SMACNA Residential Comfort System Installation Standards Manual; or

  C. The ACCA Manual J.

  Exception to Section 160.3(b)1: Block loads, the total load for all rooms combined that are served by the central equipment, may be used for the purpose of system sizing for additions. NOTE: Heating systems are required to have a minimum heating capacity adequate to meet the minimum requirements of the CBC.

  2. Design conditions . Design conditions shall be determined in accordance with the following: A. For the purpose of sizing the space-conditioning (HVAC) system, the indoor design temperatures shall be 68°F for heating and 75°F for cooling. B. Outdoor design conditions shall be selected from one of the following: i. Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X; or ii. The ASHRAE Handbook Fundamentals Volume; or

  iii. The ACCA Manual J.

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

• CALGreen § 150.0 High relevance — show source text

  Exception 2 to Section 150.0(h)7: Room air-conditioner heat pumps. 8. Sizing of electric resistance supplementary heat. Where heat pumps have electric resistance heat, the capacity of electric resistance heat shall not exceed the heat pump nominal cooling capacity (at 95°F ambient conditions) multiplied by 2.7 kW per ton, rounded up to the closest kW. 9. Capacity variation with third-party thermostats. Variable or multi-speed systems shall comply with the following requirements: A. The space conditioning system and thermostat together shall be capable of responding to heating and cooling loads by modulating system compressor speed, and meet thermostat requirements in Section 150.0(i)2. B. The installer shall certify on the Certificate of Installation that the control configuration has been tested in accordance with the testing procedure found in the CF2R.

  (i) Thermostats.

  1. Setback thermostats. All heating or cooling systems, including heat pumps, not controlled by a central energy management control system (EMCS) shall have a setback thermostat, as specified in Section 110.2(c).
  2. Thermostats that are applied to heat pumps with supplemental heating. In addition to the requirements in Section 150.0(i)1, thermostats controlling heat pumps with electric resistance supplementary heat or gas furnace supplementary heat shall comply with the following requirements: A. The thermostat shall receive outdoor air temperature from an outdoor air temperature sensor or from an internet weather service.

  B. The thermostat shall display the outdoor air temperature. C. As described in Section 150.0(h)7, the thermostat and heat pump shall lock out supplementary heat when the outdoor air temperature is above 35°F. D. The thermostat shall have an indicator to notify when supplementary heat or emergency heat is in use. E. During defrost or when the user selects emergency heating, supplementary heat operation is permitted above 35°F. F. The installer shall certify on the Certificate of Installation that the system has been tested in accordance with the testing procedure found in the CF2R.

  Exception to Section 150.0(i)2A, B, and C: Where supplementary heat is locked out above 35°F by another control device in accordance with Section 150.0(h)7.

  2025 CALIFORNIA ENERGY CODE 161

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

  SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

  Exception 1 to Section 150.0(i)2: Systems compliant with Exception 1 to Section 150.0(h)7.

  Exception 2 to Section 150.0(i)2: Room air-conditioner heat pumps.

  (j) Insulation for piping and tanks.

  1. Water piping, solar water-heating system piping, and space-conditioning system line insulation thickness and conductivity. Piping shall be insulated as follows: A. All domestic hot water piping shall be insulated as specified in Section 609.12 of the California Plumbing Code . B. Piping for space-conditioning systems, solar water-heating system collector loop, and distribution piping for steam and hydronic heating system shall meet the requirements of Section 120.3(a). Exception 1 to Section 150.0(j)1: Factory-installed piping within space-conditioning equipment certified under Section 110.1 or 110.2.

  Exception 2 to Section 150.0(j)1: Piping that penetrates framing members shall not be required to have pipe insulation for the distance of the framing penetration.