Title 24 · California Energy Code

What are the required outdoor-air (ventilation) rates and where are they specified?

Q: What table do I use to find Ra for my space?

Use the occupancy-specific area rates in Table 120.1‑A for nonresidential occupancies and the applicable Table referenced in § 160.2 for multifamily entries; pick the row that matches your occupancy category.

Q: Can I count air transferred from another space as outdoor air?

Yes — but only if transfer air is used per the code’s transfer‑air rules and the combined outdoor air supplied to all spaces meets each space’s requirement (see the transfer‑air exception in § 120.1(c)3 / § 160.2(c)3 ).

For a homeowner: the Energy Code requires mechanically ventilated spaces to get outdoor air equal to whichever is larger — 15 cubic feet per minute for each expected person, or a minimum cfm per square foot listed in the code table — and it includes special rules for multifamily units, demand control ventilation, and transfer air.

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Last reviewed: July 6, 2026

What the code requires — plain English

The California Energy Code requires that mechanically ventilated occupiable spaces receive an outdoor-air rate equal to the larger of an occupant-based or an area‑based minimum. This is stated in § 120.1(c)3 for nonresidential systems and mirrored for multifamily/common spaces in § 160.2(c)3. Both sections implement the Equation Vz = max(Rp × Pz, Ra × Az), where Rp = 15 cfm/person and Ra is the area-based value taken from the applicable Table (Table 120.1‑A or Table 160.2‑B).

The single most important rule: supply at least the larger of (a) 15 cfm per expected occupant, or (b) the area-based cfm/ft² from the applicable code table — calculated per ventilation zone.

Requirements in detail

Core equation and defined terms

Ventilation zone (Vz) — the zone-level outdoor airflow required by the code; computed with Vz = the larger of Rp×Pz or Ra×Az. § 120.1(c)3 and § 160.2(c)3 specify this calculation.
Rp (people rate) = 15 cfm/person (explicit in both §120.1(c)3 and §160.2(c)3).
Ra (area rate) = the area‑based minima listed in the code tables (Table 120.1‑A for nonresidential; Table 160.2‑B / Table 160.2‑C family for multifamily/related tables).

Key control & design requirements

Systems must be designed with ductwork, dampers and controls to operate at the minimum outdoor-air rates in § 160.2(c)3 (and §120.1(c)3 for nonresidential). Variable-air systems must include dynamic controls to maintain outdoor‑air within ±10% of the required rate. Fixed minimum damper positions are not an acceptable dynamic control strategy.
Demand-control ventilation (DCV) / CO2 control and occupant-sensor strategies are permitted/required in specified situations; see the DCV thresholds and sensor requirements under the related subsections.

Decision-relevant table (common values & references)

Decision dimension	Typical value (code)	Where code gives it	Code Reference
People outdoor-air rate (Rp)	15 cfm/person	Equation in §120.1(c)3 / §160.2(c)3	§ 120.1(c)3, § 160.2(c)3
Area-based rate (Ra) — example: classroom	0.15 cfm/ft²	Table 120.1‑A (nonresidential table)	Table 120.1‑A (see § 120.1(c)3)
Area-based rate (Ra) — example: restaurant dining	0.15 cfm/ft²; bars 0.20 cfm/ft²	Table 120.1‑A entries	Table 120.1‑A (see § 120.1(c)3)
Whole‑dwelling (multifamily) total ventilation	Qtot = 0.03 × Afloor + 7.5 × (Nbr + 1) (cfm)	Equation 160.2‑B (whole-dwelling unit)	§ 160.2(c) / Equation 160.2‑B
DCV (when required) — sensor setpoint	600 ppm above outdoor CO₂ (CO₂ control limit)	Demand control requirements	§ 120.1(d)4 / § 160.2(c)5D
DCV minimum occupancy threshold	Spaces with design density ≥ 25 people/1,000 ft² (i.e., ≤ 40 ft²/person)	DCV applicability rules	§ 120.1(d)3 / § 160.2(c)5C

(Use the specific occupancy category and the table row for Ra and the specified occupancy density to compute Pz and Ra×Az for your zone.)

Exceptions & special cases

Transfer air allowed: The outdoor-air rate required by § 120.1(c)3 (and § 160.2(c)3) may be provided via transfer air from other ventilated spaces if transfer is used in accordance with the applicable transfer‑air rules and the combined outdoor air supplied to all spaces meets each space’s requirement.
Demand control ventilation (DCV) exceptions: DCV is not permitted in spaces that generate dusts, fumes, mists, vapors or gases and that lack local exhaust (e.g., unvented food service, certain labs, barbers/beauty/nail salons, daycare sickrooms) or when the space is very small (area < 150 ft²) or design occupancy < 10 people per the DCV exception language.
Preoccupancy purge: The code requires supplying the lesser of the minimum rate or three complete air changes to the building during the 1‑hour preoccupancy purge period in some provisions. See preoccupancy rules in the relevant section.
Multifamily whole-dwelling approach: For dwelling units in multifamily buildings, use the whole-dwelling equation Qtot = 0.03 Afloor + 7.5(Nbr+1) and follow the CFI/compartmentalization and balanced/supply ventilation requirements in §160.2.

Common mistakes

Relying on a single rule-of-thumb (e.g., cfm/person only) without checking the area-based Ra — the code requires taking the larger of Rp×Pz or Ra×Az.
Using a fixed minimum damper position and calling it “dynamic control.” The code requires dynamic controls that hold outdoor-air within ±10% of the required rate for VAV systems. Fixed positions are not acceptable.
Forgetting transfer-air rules: counting transferred air as outdoor air without meeting the transfer‑air provisions will lead to noncompliance.
Misapplying DCV: applying CO₂-based DCV where the space is disallowed (process-generating contaminants) or failing to locate/validate CO₂ sensors per the code (sensor heights, accuracy and calibration requirements).

Worked example — restaurant dining room

Scenario: A restaurant dining room is 1,500 ft². Table 120.1‑A lists dining rooms at 33 people/1,000 ft² and Ra = 0.15 cfm/ft². Compute the ventilation required for the zone per § 120.1(c)3.

Determine expected occupants (Pz):
Pz = 33 persons / 1,000 ft² × 1,500 ft² = 49.5 ≈ 50 persons.
People-based outdoor air: Rp × Pz = 15 cfm/person × 50 persons = 750 cfm.
Area-based outdoor air: Ra × Az = 0.15 cfm/ft² × 1,500 ft² = 225 cfm.
Required outdoor air to the zone = larger of the two → 750 cfm (use this value for design and controls). § 120.1(c)3 applies.

Notes: If this system meets the DCV thresholds (density ≥ 25/1,000 ft², or design cfm > 3,000, or has an economizer), DCV rules and CO₂ sensor placement / setpoints apply. Otherwise design must still provide the full Vz and have the controls to maintain it within 10%.

Related provisions (quick list)

§ 120.1(c)3 — Required outdoor air for nonresidential systems (core equation and Ra/Rp)
§ 160.2(c)3 — Multifamily ventilation rate requirements; mirrors the Vz equation and transfer‑air rules for multifamily buildings
§ 160.2‑B (Equation) — Whole‑dwelling unit ventilation calculation (Qtot = 0.03 Afloor + 7.5(Nbr+1)) for multifamily dwelling units
§ 120.1(d)3 / § 160.2(c)5C — Demand control ventilation (DCV) applicability thresholds (≥25 people/1,000 ft², etc.)
§ 120.1(d)4 / § 160.2(c)5D — CO₂ sensor requirements and DCV control (600 ppm + outdoor baseline setpoint; sensor location and calibration)
§ 120.1(g) / § 160.2(c)8 — Transfer-air and air‑class recirculation limitations (when transfer or recirculation is allowed)

Code references

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

§ 62.1 High relevance — show source text

Controls shall be designed to coordinate operation of the natural and mechanical ventilation systems. [ASHRAE 62.1:6.4.3] D. Naturally ventilated spaces shall also include a mechanical ventilation system designed in accordance with Section 120.1(c)3. Exception 1 to Section 120.1(c)2D: Spaces not served by a space-conditioning system. Exception 2 to Section 120.1(c)2D: Spaces where natural ventilation openings complying with Section 120.1(c)2 are either permanently open or have controls that prevent the openings from being closed during periods of expected occupancy. 3. Mechanical ventilation. Occupiable spaces shall be ventilated with a mechanical ventilation system capable of providing an outdoor airflow rate to the zone ( V z ) no less than Equation 120.1-F as described below:

(Equation 120.1-F) V z = The larger of R p × P z or R a × A z

Where:

R p = 15 cubic feet per minute of outdoor airflow per person P z = The expected number of occupants. For spaces without fixed seating, the expected number of occupants shall be the expected number specified by the building designer or the default occupancy density in Table 120.1-A times the occupiable floor area of the zone, whichever is greater. For spaces with fixed seating, the expected number of occupants shall be determined in accordance with Section 1004.6 of the California Building Code. R a = The area-based minimum ventilation airflow rate in Table 120.1-A. A z = The net occupiable floor area of the ventilation zone in square feet.

Exception 2 to Section 120.1(c)3: Transfer air. The rate of outdoor air required by Section 120.1(c)3 may be provided with air transferred from other ventilated space if: A. Use of transfer air is in accordance with Section 120.1(g); and B. The outdoor air that is supplied to all spaces combined, is sufficient to meet the requirements of Section 120.1(c)3 for each space individually. 4. Exhaust ventilation. The design exhaust airflow shall be determined in accordance with the requirements in Table 120.1-B. Exhaust makeup air shall be permitted to be any combination of outdoor air, recirculated air, or transfer air.

[ASHRAE 62.1:6.5.1]

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TABLE 120.1-A—MINIMUM VENTILATION RATES	Col2	Col3	Col4	Col5
OCCUPANCY CATEGORY	MINIMUM OCCUPANT LOAD DENSITY (persons/1,000 ft2)	AREA-BASED MINIMUM VENTILATION_ Ra_ (cfm/ft2)	AIR CLASS	NOTES
Educational Facilities	Educational Facilities	Educational Facilities	Educational Facilities	Educational Facilities
Daycare (through age 4)	14	0.

§ 403.2.1. High relevance — show source text
Pz = Zone population: see Section 403.2.1. Ra = Area outdoor air rate, CFM/ft [2] . See Section 403.2.1.

Rp = People outdoor air rate, CFM/person. See Section 403.2.1.

Vbz = Breathing zone outdoor airflow, CFM. See Section 403.2.1.

Vdz = Zone discharge airflow, CFM. The expected discharge (supply) airflow to the zone that includes primary airflow and secondary recirculated airflow, CFM.

Vot = Outdoor air intake flow, CFM. See Section 403.3, Section 403.4, and Section 403.5.2.

Vou = Uncorrected outdoor air intake, CFM. See Section 403.5.1.

Voz = Zone outdoor airflow, CFM. See Section 403.2.3. Vps = System primary airflow, CFM. The total primary airflow supplied to all zones served by the system from the air-handling unit at which the outdoor air intake is located.

Vpz = Zone primary airflow, CFM. The zone primary airflow to the ventilation zone, including outdoor air and recirculated air.

Xs = Average outdoor air fraction: At the primary air handler, the fraction of outdoor air intake flow in the system primary airflow. Zpz = Primary outdoor air fraction: The outdoor air fraction required in the primary air supplied to the ventilation zone prior to the introduction of any secondary recirculation air. [ASHRAE 62.1:A3]

For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute =

0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per

minute per square foot = 5.08 [(L/s)/m [2] ]

405.0 Ventilation for Residential Occupancies.

405.1 General. Rooms or occupied spaces within residential occupancies, where the occupants are nontransient, shall be designed to have mechanical ventilation and exhaust air in accordance with Section 405.2 through Section 405.5.

405.1.1 Natural Ventilation. Where approved by the Authority Having Jurisdiction, natural ventilation shall be permitted for Climate Zone 1, Climate Zone 2, or for thermally conditioned buildings for less than 876 hours

per year.

405.2 Ventilation Air Rate. The required mechanical ventilation outdoor air rate ( Qtot ) shall be as calculated in accordance with Equation 405.2.

Exception: For existing buildings and where permitted by the Authority Having Jurisdiction, the total mechanical ventilation ( Qtot ) is not required where Qtot is calculated to be less than 15 ft [3] /min (7.08 L/s).

Qtot = 0.03 Afloor + 7.5 ( Nbr + 1) (Equation 405.2)

Where:

Qtot = Total required ventilation outdoor air rate, CFM (L/s) Afloor = Floor area, ft [2] (m [2] ) Nbr = Number of bedrooms more than 1

For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s
§ 160.2 High relevance — show source text
7. Design and control requirements for quantities of outdoor air . A. All mechanical ventilation and space-conditioning systems shall be designed with and have installed ductwork, dampers and controls to allow outside air rates to be operated at the minimum levels specified in Section 160.2(c)3 or the rate required for make-up of exhaust systems that are required for an exempt or covered process, for control of odors or for the removal of contaminants within the space. B. All variable air volume mechanical ventilation and space-conditioning systems shall include dynamic controls that maintain measured outside air ventilation rates within 10 percent of the required outside air ventilation rate at both full and reduced supply airflow conditions. Fixed minimum damper position is not considered to be dynamic and is not an allowed control strategy. C. Measured outdoor air rates of constant volume mechanical ventilation and space-conditioning systems shall be within 10 percent of the required outside air rate.

8. Air classification and recirculation limitations. Air classification and recirculation limitations of air shall be based on the air classification as listed in Table 160.2-B or Table 160.2-D, in accordance with the following: A. Class 1 air is air with low contaminant concentration, low sensory-irritation intensity or inoffensive odor. Recirculation or transfer of Class 1 air to any space shall be permitted; [ASHRAE 62.1:5.13.3.1] B. Class 2 air is air with moderate contaminant concentration, mild sensory-irritation intensity or mildly offensive odor (Class 2 air also includes air that is not necessarily harmful or objectionable but that is inappropriate for transfer or recirculation to spaces used for different purposes). Recirculation or transfer of Class 2 air shall be permitted in accordance with Sections 160.2(c)8Bi through 160.2(c)8Bv: i. Recirculation of Class 2 air within the space of origin shall be permitted [ASHRAE 62.1:5.13.3.2.1]. ii. Recirculation or transfer of Class 2 air to other Class 2 or Class 3 spaces shall be permitted, provided that the other spaces are used for the same or similar purpose or task and involve the same or similar pollutant sources as the Class 2 space [ASHRAE 62.1:5.13.3.2.2]; or iii. Transfer of Class 2 air to toilet rooms [ASHRAE 62.1:5.13.3.2.3]; or

iv. Recirculation or transfer of Class 2 air to Class 4 spaces [ASHRAE 62.1:5.13.3.2.4]. v. Class 2 air shall not be recirculated or transferred to Class 1 spaces. [ASHRAE 62.1:5.13.3.2.5]. Exception to Section 160.2(c)8Bv: When using any energy recovery device, recirculation from leakage, carryover or transfer from the exhaust side of the energy recovery device is permitted. Recirculated Class 2 air shall not exceed 10 percent of the outdoor air intake flow. C. Class 3 air is air with significant contaminant concentration, significant sensory-irritation intensity or offensive odor. Recirculation or transfer of Class 3 air shall be permitted in accordance with Sections 160.2(c)8Ci and 160.2(c)8Cii: i. Recirculation of Class 3 air within the space of origin shall be permitted.
§ 160.2 High relevance — show source text
Exception 2 to Section 160.2(c)2D: Spaces where natural ventilation openings complying with Section 120.1(c)2 are either permanently open or have controls that prevent the openings from being closed during periods of expected

occupancy. 3. Mechanical ventilation. Occupiable spaces shall be ventilated with a mechanical ventilation system capable of providing an outdoor airflow rate ( V z ) to the zone no less than the Equation 160.2-H as described below: (Equation 160.2-H) V z = The larger of R p × P z or R a × A z where:

R p = 15 cubic feet per minute of outdoor airflow per person. P z = The expected number of occupants. For spaces without fixed seating, the expected number of occupants shall be the expected number specified by the building designer or the default occupancy density in Table 160.2-B times the occupiable floor area of the zone, whichever is greater. For spaces with fixed seating, the expected number of occupants shall be determined in accordance with the California Building Code Section 1004.6. R a = The area-based minimum ventilation airflow rate in Table 160.2-B. A z = The net occupiable floor area of the ventilation zone in square feet. Exception to Section 160.2(c)3: Transfer air. The rate of outdoor air required by Section 160.2(c)3 may be provided with air transferred from other ventilated space if: i. Use of transfer air is in accordance with Section 160.2(c)8; and

ii. The outdoor air that is supplied to all spaces combined is sufficient to meet the requirements of Section 160.2(c)3 for each space individually. 4. Exhaust ventilation. The design exhaust airflow shall be determined in accordance with the requirements in Table 160.2-C. Exhaust makeup air shall be permitted to be any combination of outdoor air, recirculated air or transfer air. [ASHRAE 62.1:6.5.1] 5. Operation and control requirements for minimum quantities of outdoor air . A. Times of occupancy. The minimum rate of outdoor air required by Section 160.2(c) shall be supplied to each space at all times when the space is usually occupied. Exception 1 to Section 160.2(c)5A: Demand control ventilation. In intermittently occupied spaces that do not have processes or operations that generate dusts, fumes, mists, vapors or gases and are not provided with local exhaust ventilation (such as indoor operation of internal combustion engines or areas designated for unvented food service

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preparation), the rate of outdoor air may be reduced if the ventilation system serving the space is controlled by a demand control ventilation device complying with Section 160.2(c)5D or by an occupant sensor ventilation control device complying with Section 160.2(c)5E. Exception 2 to Section 160.2(c)5A: Temporary reduction. The rate of outdoor air provided to a space may be reduced below the level required by Section 160.2(c) for up to 30 minutes at a time if the average rate for each hour is equal to or greater than the required ventilation rate. B. **Preoccupancy.
§ 140.4 High relevance — show source text
b. DOAS cooling coils shall be hydronic cooling coils utilizing space-cooling chilled water loop. ii. Other heating or cooling shall be provided by a heat pump. Electric resistance heating shall not be used. F. Parallel fan-powered boxes used to comply with Section 140.4(a)3Aiii shall use recirculated zone or plenum air shall be used in heating mode. Fans shall cycle on only when there is a demand for heating and shall have a maximum fan power of 0.3 W/cfm at design airflow. Terminal units providing ventilation air shall be set to no greater than the minimum ventilation rate when the zone is in deadband or in heating mode.

(b) Calculations. In making equipment sizing calculations under Subsection (a), all of the following rules shall apply:
1. Heating and cooling loads. Heating and cooling system design loads shall be determined in accordance with the procedures described in Subsection A or B below:
A. For systems serving hotel/motel buildings, and nonresidential buildings other than healthcare facilities, the method in the 2017 ASHRAE Handbook, Fundamentals shall be used or as specified in a method approved by the Commission. B. For system serving healthcare facilities the method in the California Mechanical Code shall be used. 2. Indoor design conditions. Indoor design temperature and humidity conditions for comfort applications shall be determined in accordance with Subsection A or B below:

A. For systems serving hotel/motel buildings, and nonresidential buildings other than healthcare facilities, ASHRAE Standard 55 or the 2017 ASHRAE Handbook, Fundamentals Volume, except that winter humidification and summer dehumidification shall not be required. B. For systems serving healthcare facilities the method in the California Mechanical Code shall be used. 3. Outdoor design conditions. Outdoor design conditions shall be selected in accordance with Subsection A or B below: A. For systems serving hotel/motel buildings and nonresidential buildings other than healthcare facilities the design conditions shall meet the following: i. 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. ii. Heating design temperatures shall be no lower than the 99.0 percent Heating Dry Bulb or the Heating Winter Median of Extremes values.

iii. Cooling design temperatures shall be no greater than the 0.5 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.

B. For system serving healthcare facilities the method in Section 320.0 of the California Mechanical Code shall be used. Exception to Section 140.4(b)3: Cooling design temperatures for cooling towers shall be no greater than the 0.5 percent cooling design wet bulb values. 4. Ventilation. Outdoor air ventilation loads shall be calculated using the ventilation rates required in Section 120.1(c)3. 5. Envelope. Envelope heating and cooling loads shall be calculated using envelope characteristics, including square footage, thermal conductance, Solar Heat Gain Coefficient or shading coefficient, and air leakage, consistent with the proposed design. 6. Lighting. Lighting heating and cooling loads shall be based on actual design lighting levels or power densities as specified in Section 140.6.

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§ 120.1 High relevance — show source text
1. Pre-occupancy. The lesser of the minimum rate of outdoor air required by Section 120.1(c) or three complete air changes shall be supplied to the entire building during the one-hour period immediately before the building is normally occupied.
2. Required demand control ventilation. Demand ventilation controls complying with Section 120.1(d)4 are required for a space with a design occupant density, or a maximum occupant load factor for egress purposes in the CBC, greater than or equal to 25 people per 1,000 square feet (40 square feet or less per person) if the ventilation system serving the space has one or more of the following:
A. An air economizer; or

B. Modulating outside air control; or C. Design outdoor airflow rate > 3,000 cfm. Exception 1 to Section 120.1(d)3: Where space exhaust is greater than the design ventilation rate specified in Section 120.1(c)3 minus 0.2 cfm per square foot of conditioned area. Exception 2 to Section 120.1(d)3: Spaces that have processes or operations that generate dusts, fumes, mists, vapors or gases and are not provided with local exhaust ventilation, such as indoor operation of internal combustion engines or areas designated for unvented food service preparation, daycare sickrooms, science labs, barber shops or beauty and nail salons shall not install demand control ventilation.

Exception 3 to Section 120.1(d)3: Spaces with an area of less than 150 square feet, or a design occupancy of less than 10 people as specified by Section 120.1(c)3.
1. Demand control ventilation devices.
A. For each system with demand control ventilation (DCV), CO 2 sensors shall be installed in each room that meets the criteria of Section 120.1(d)3 with no less than one sensor per 10,000 square feet of floor space. When a zone or a space is served by more than one sensor, a signal from any sensor indicating that CO 2 is near or at the setpoint within the zone or space, shall trigger an increase in ventilation. B. CO 2 sensors shall be located in the room between 3 feet and 6 feet above the floor or at the anticipated height of the occupants’ heads. C. Demand ventilation controls shall maintain CO 2 concentrations less than or equal to 600 ppm plus the outdoor air CO 2 concentration in all rooms with CO 2 sensors. Exception to Section 120.1(d)4C: The outdoor air ventilation rate is not required to be larger than the design outdoor air ventilation rate required by Section 120.1(c)3 regardless of CO 2 concentration. D. Outdoor air CO 2 concentration shall be determined by one of the following: i. CO 2 concentration shall be assumed to be 400 ppm without any direct measurement; or ii. CO 2 concentration shall be dynamically measured using a CO 2 sensor located within 4 feet of the outdoor air intake.

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§ 160.2 High relevance — show source text
B. Preoccupancy. The lesser of the minimum rate of outdoor air required by Section 160.2(c) or three complete air changes shall be supplied to the entire building during the 1-hour period immediately before the building is normally occupied. C. Required demand control ventilation. Demand ventilation controls complying with Section 160.2(c)5D are required for a space with a design occupant density, or a maximum occupant load factor for egress purposes in the CBC, greater than or equal to 25 people per 1000 square feet (40 square feet or less per person) if the system serving the space has one or more of the following:

i. An air economizer; or

ii. Modulating outside air control; or iii. Design outdoor airflow rate > 3,000 cfm. Exception 1 to Section 160.2(c)5C: Where space exhaust is greater than the design ventilation rate specified in Section 160.2(c)3 minus 0.2 cfm per ft2 of conditioned area. Exception 2 to Section 160.2(c)5C: Spaces that have processes or operations that generate dusts, fumes, mists, vapors or gases and are not provided with local exhaust ventilation, such as indoor operation of internal combustion engines or areas designated for unvented food service preparation, daycare sickrooms, science labs, barber shops or beauty and nail salons, shall not install demand control ventilation. Exception 3 to Section 160.2(c)5C: Spaces with an area of less than 150 square feet or a design occupancy of less than 10 people as specified by Section 160.2(c)3.

D. Demand control ventilation devices.

i. For each system with demand control ventilation (DCV), CO 2 sensors shall be installed in each room that meets the criteria of Section 160.2(c)5C with no fewer than one sensor per 10,000 ft2 of floor space. When a zone or a space is served by more than one sensor, a signal from any sensor indicating that CO 2 is near or at the setpoint within the zone or space shall trigger an increase in ventilation. ii. CO 2 sensors shall be located in the room between 3 ft and 6 ft above the floor or at the anticipated height of the occupants’ heads. iii. Demand ventilation controls shall maintain CO 2 concentrations less than or equal to 600 ppm plus the outdoor air CO 2 concentration in all rooms with CO 2 sensors. Exception to Section 160.2(c)5Diii: The outdoor air ventilation rate is not required to be larger than the design outdoor air ventilation rate required by Section 160.2(c)3 regardless of CO 2 concentration. iv. Outdoor air CO 2 concentration shall be determined by one of the following: a. CO 2 concentration shall be assumed to be 400 ppm without any direct measurement; or b. CO 2 concentration shall be dynamically measured using a CO 2 sensor located within 4 ft of the outdoor air intake.

v. When the system is operating during hours of expected occupancy, the controls shall maintain system outdoor air ventilation rates no less than R a × A z per Equation 160.2-H for each space with a CO 2 sensor(s), plus the greater of either the exhaust air rate or the rate required by Section 160.2(c)3 for other spaces served by the system. vi.
§ 403.0 High relevance — show source text
403.0 Ventilation Rates. [Not permitted for OSHPD 1, 2, 3, 4 & 5 spaces listed in Table 4-A]

403.1 General. The design outdoor air intake flow rate for a ventilation system shall be determined in accordance with Section 403.2 through Section 403.10.

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VENTILATION AIR

403.2 Zone Calculations. Ventilation zone parameters shall be determined in accordance with Section 403.2.1 through Section 403.2.3 for ventilation zones served by the ventilation system, except that the ventilation rates from ASHRAE/ASHE 170 shall be used for the occupancy categories, as applicable. [ASHRAE 62.1:6.2.1]

403.2.1 Breathing Zone Outdoor Airflow. The outdoor airflow required in the breathing zone ( Vbz ) of the occupiable space or spaces in a ventilation zone shall be not less than the value determined in accordance with Equation 403.2.1.

Vbz = Rp•Pz + Ra• Az (Equation 403.2.1)

Where: Az = zone floor area, the net occupiable floor area of the ventilation zone, ft [2] (m [2] ). Pz = zone population, the number of people in the ventilation zone during usage. Rp= outdoor airflow rate required per person (CFM/person) as determined from Table 402.1. Ra= outdoor airflow rate required per unit area (CFM/ft [2] ) as determined from Table 402.1.

[ASHRAE 62.1:6.2.1.1] For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per minute per square foot = 5.08 [(L/s)/m [2] ] 403.2.2 Zone Air Distribution Effectiveness. The zone air distribution effectiveness ( Ez ) shall be determined in accordance with Table 403.2.2. [ASHRAE 62.1:6.2.1.2] 403.2.2.1 Stratified Air Distribution Systems. A stratified air distribution system shall be designed in accordance with Section 403.2.2.1.1 through Section 403.2.2.2.2, or the zone air distribution effectiveness ( Ez ) shall be determined in accordance with ASHRAE 62.1. [ASHRAE 62.1:6.2.1.2.1] 403.2.2.1.1 Supply Air. Cool air shall be at least 4°F (2°C) less than the average room air temperature. [ASHRAE 62.1:6.2.1.2.1.1] 403.2.2.1.2 Return Air. The return air openings or pathways shall be located not less than 9 feet (2743 mm) above the floor. [ASHRAE 62.1:6.2.1.2.1.2]
§ 605.1.3 High relevance — show source text
E 605.1.3 Dwelling Unit Ventilation. A mechanical exhaust system, supply system, or combination thereof shall be designed and provided with the capacity to deliver outdoor air ventilation to the whole dwelling unit at a continuous rate not less than that specified in Section E 605.1.3.1 through Section E 605.1.3.5. [ASHRAE 62.2:4.1]

E 605.1.3.1 Total Ventilation Rate. The total required ventilation rate ( Qtot ) shall be as specified in Table E 605.1.3.1 or, alternatively, calculated using Equation E 605.1.3.1.

(Equation E 605.1.3.1) Qtot = 0.03 Afloor + 7.5( Nbr + 1)

Where:

Qtot = total required ventilation rate, CFM Afloor = dwelling unit floor area, ft [2] Nbr = number of bedrooms (not to be less than one)

For SI units: 1 cubic foot per minute = 0.00047 m [3] /s, 1 cubic foot

per minute = 0.4719 L/s

Exceptions: Dwelling-unit mechanical ventilation systems shall not be required where the Authority Having Jurisdiction determines that window operation is a locally permissible method of providing ventilation and provided one or more of the following conditions is met:

(1) The building has no mechanical cooling and is in zone 1 or 2 of the climate zone map.

(2) The building is thermally conditioned for human occupancy for less than 876 hours per year. [ASHRAE 62.2:4.1.1] E 605.1.3.2 Effective Annual Average Infiltra- tion Rate ( Qinf ) Using a Single-Point Enve- lope Leakage Test. Effective Annual Average

Infiltration Rate ( Qinf ) shall be calculated using a single-point test at 0.007 psi (50 Pa). The Effective Annual Average Infiltration Rate ( Qinf ) shall be calculated using Equation 605.1.3.2:

(Equation E 605.1.3.2) Qinf = 0.052 × Q 50 × wsf × ( H/Hr ) [z]

Where: Qinf = estimated infiltration rate, CFM (L/s). Q50 = leakage rate at 0.007 psi (50 Pa) depressurization or pressurization, CFM (L/s). wsf = weather and shielding factor from ASHRAE 62.2.

H = vertical distance between the lowest and highest above-grade points within the pressure boundary, ft (m). Hr = reference height, 8.2 ft (2.5 m). z = 0.4 for the purpose of calculating the Effective Annual Average Infiltration Rate.

For SI units: 1 foot = 0.3048 m, 1 cubic foot per minute =

0.4719 L/s

§ 120.1 High relevance — show source text

[ASHRAE 62.1:6.5.1]

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NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS

TABLE 120.1-A—MINIMUM VENTILATION RATES	Col2	Col3	Col4	Col5
OCCUPANCY CATEGORY	MINIMUM OCCUPANT LOAD DENSITY (persons/1,000 ft2)	AREA-BASED MINIMUM VENTILATION_ Ra_ (cfm/ft2)	AIR CLASS	NOTES
Educational Facilities	Educational Facilities	Educational Facilities	Educational Facilities	Educational Facilities
Daycare (through age 4)	14	0.15	2	—
Daycare sickroom	5	0.15	3	—
Classrooms (ages 5–8)	25	0.15	1	—
Classrooms (age 9–18)	25	0.15	1	—
Lecture/postsecondary classroom	25	0.15	1	F
Lecture hall (fixed seats)	-71	0.15	1	F
Art classroom	25	0.15	2	—
Science laboratories	25	0.15	2	—
University/college laboratories	25	0.15	2	—
Wood/metal shop	10	0.15	2	—
Computer lab	25	0.15	1	—
Media center	25	0.15	1	A
Music/theater/dance	33	0.15	1	F
Multiuse assembly	33	0.15	1	F
Food and Beverage Service	Food and Beverage Service	Food and Beverage Service	Food and Beverage Service	Food and Beverage Service
Restaurant dining rooms	33	0.15	2	—
Cafeteria/fast-food dining	33	0.15	2	—
Bars, cocktail lounges	33	0.20	2	—
Kitchen (cooking)	3	0.

§ 160.2 High relevance — show source text
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.

d. 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 160.2(b)2Aiv. During periods when comfort conditioning is not called for by the space-conditioning thermostat, the CFI ventilation system controls shall operate the space-conditioning system central fan and outdoor air damper(s) when necessary to ensure compliance with the minimum outdoor air ventilation required by Section 160.2(b)2Aiv in accordance with applicable variable mechanical ventilation methods specified in ASHRAE 62.2 Section 4.5.

iii. Air filtration. Air filtration shall conform to the specifications in Section 160.2(b)1. Compliance with ASHRAE 62.2 Sections 6.7 (Minimum Filtration) and 6.7.1 (Filter Pressure Drop) shall not be required. iv. Whole-dwelling unit mechanical ventilation . Multifamily attached dwelling units shall comply with Subsections a and b below.

a. Mechanical ventilation airflow shall be provided at rates greater than or equal to the value determined in accordance with Equation 160.2-B. Total Required Ventilation Rate [ASHRAE 62.2:4.1.1]: (Equation 160.2-B) Q tot = 0.03 A floor + 7.5( N br + 1)

where:

Q tot = total required ventilation rate, cfm. A floor = dwelling-unit floor area, ft [2] . N br = number of bedrooms (not to be less than 1). b. All dwelling units in a multifamily building shall use the same whole-dwelling unit ventilation system type. The dwelling unit shall comply with Subsections 1 and 2 below.
1. Balanced or supply ventilation . A balanced or supply ventilation system shall provide the required whole-dwelling-unit ventilation airflow. Balanced systems with heat recovery or energy recovery that serve a single dwelling unit shall have a fan efficacy of ≤1.0 W/cfm; and
2. Compartmentalization testing. The air leakage rate shall not exceed 0.3 cubic feet per minute at 50 Pa (0.2 inch water) per ft [2] of dwelling unit envelope surface area as confirmed by ECC-Rater field verification and diagnostic testing in accordance with the procedures specified in Reference Appendix RA3.8 or NA2.3 as applicable. In multifamily buildings with four or more habitable stories,
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the field verification and diagnostic testing which requires an ECC-Rater may alternatively be performed by a certified Mechanical Acceptance Test Technician according to the requirements specified in Reference Appendix NA1.9. v. Multifamily building central ventilation system airflow rate tolerance. Multifamily building central ventilation systems that serve multiple dwelling units shall have airflow rates in each dwelling unit served that meet or exceed a design ventilation airflow rate specification.
§ 1-2006 High relevance — show source text
1. Fractional HVAC motors for fans. HVAC motors for fans that are less than 1 hp and [1] / 12 hp or greater shall be electronicallycommutated motors or shall have a minimum motor efficiency of 70 percent when rated in accordance with NEMA Standard MG 1-2006 at full load rating conditions. These motors shall also have the means to adjust motor speed for either balancing or remote control. Belt-driven fans may use sheave adjustments for airflow balancing in lieu of a varying motor speed. Exception 1 to Section 140.4(c)3: Motors in fan-coils and terminal units that operate only when providing heating to the space served. Exception 2 to Section 140.4(c)3: Motors in space conditioning equipment certified under Section 110.1 or 110.2.
Exception to Section 140.4(c): Fan system power caused solely by process loads.

(d) Space-conditioning zone controls. Each space-conditioning zone shall have controls designed in accordance with 1 or 2:
1. Each space-conditioning zone shall have controls that prevent: A. Reheating; and B. Recooling; and C. Simultaneous provisions of heating and cooling to the same zone, such as mixing or simultaneous supply of air that has been previously mechanically heated and air that has been previously cooled, either by cooling equipment or by economizer systems; or
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COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY
1. Zones served by variable air-volume systems that are designed and controlled to reduce, to a minimum, the volume of reheated, recooled, or mixed air are allowed only if the controls meet all of the following requirements: A. For each zone with direct digital controls (DDC): i. The volume of primary air that is reheated, recooled or mixed air supply shall not exceed the larger of: a. 50 percent of the peak primary airflow; or b. The design zone outdoor airflow rate as specified by Section 120.1(c)3. ii. The volume of primary air in the deadband shall not exceed the design zone outdoor airflow rate as specified by Section 120.1(c)3. iii. The first stage of heating consists of modulating the zone supply air temperature setpoint up to a maximum setpoint no higher than 95ºF while the airflow is maintained at the dead band flow rate. iv. The second stage of heating consists of modulating the airflow rate from the dead band flow rate up to the heating maximum flow rate. v. Control sequences of operation for reheat zones shall be in accordance with ASHRAE Guideline 36. B. For each zone without DDC, the volume of primary air that is reheated, re-cooled, or mixed air supply shall not exceed the larger of the following: i. 30 percent of the peak primary airflow; or ii. The design zone outdoor airflow rate as specified by Section 120.1(c)3.
Exception 1 to Section 140.4(d): Zones with special pressurization relationships or cross-contamination control needs.

Exception 2 to Section 140.4(d): Zones served by space-conditioning systems in which at least 75 percent of the energy for reheating, or providing warm air in mixing systems, is provided from a site-recovered or site-solar energy source.

Frequently asked questions

What table do I use to find Ra for my space?

Use the occupancy-specific area rates in Table 120.1‑A for nonresidential occupancies and the applicable Table referenced in § 160.2 for multifamily entries; pick the row that matches your occupancy category.

When can I use demand-control ventilation (DCV)?

DCV is required or allowed for intermittently occupied/high-density spaces meeting the thresholds in § 120.1(d)3 or § 160.2(c)5C (e.g., design density ≥ 25 people/1,000 ft²) except where prohibited by process-generated contaminants.

Can I count air transferred from another space as outdoor air?

Yes — but only if transfer air is used per the code’s transfer‑air rules and the combined outdoor air supplied to all spaces meets each space’s requirement (see the transfer‑air exception in § 120.1(c)3 / § 160.2(c)3).

How do I size CO₂ sensors for DCV?

CO₂ sensors must be located 3–6 ft above the floor, meet accuracy/calibration requirements, and be no less than one sensor per 10,000 ft² where DCV is applied; DCV controls must hold CO₂ ≤ 600 ppm + outdoor CO₂ baseline. See § 120.1(d)4 and § 160.2(c)5D.

Do variable-air systems have additional controls?

Yes — variable air volume systems must include dynamic controls that maintain measured outside‑air ventilation within 10% of the required outside‑air rate at both full and reduced supply-flow conditions.

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California Energy Code