Title 24 · California Energy Code
When is demand-control ventilation (DCV) required and how must it be tested?
If a room is large (>500 sq ft), dense (≥25 people per 1,000 sq ft), and served by an economizer or modulating outside-air control (or >3,000 cfm OA), California code requires demand-control ventilation. Install CO2 sensors (at least one per room and ≥1 per 10,000 sq ft), place them 3–6 ft high, use setpoints ≤600 ppm + outdoor (or ≤1000 ppm if no outdoor sensor), and perform acceptance tests that simulate CO2 above and below the setpoint to verify the outdoor-air damper modulates as required (tests described in NA7.5.5 and CMC Appendix E E 805.6).
Last reviewed: July 6, 2026
What the code requires — plain English
The California code requires demand-control ventilation (DCV) when a space exceeds certain area, occupant-density, and system triggers so outdoor air can be reduced when occupancy is below design. The DCV trigger language is shown in § 120.1(d)3 in the retrieved code text. Acceptance testing for DCV is required by § 120.5 (tests per NA7.5.5), and the California Mechanical Code Appendix E provides the functional test steps and acceptance criteria in E 805.6.
The single most important rule: If a space is large enough, dense enough, and served by an economizer (or modulating OA control or >3,000 cfm OA), DCV must be provided and must be functionally tested so CO2-based controls correctly modulate outdoor air.
Requirements in detail
Summary decision dimensions (quick reference)
| Decision dimension | Threshold / required value (bolded) | How applied | Code Reference |
|---|---|---|---|
| Space area | > 500 sq ft | Space must be larger than this to be eligible for the DCV trigger | § 120.1(d)3 |
| Occupant density (design) | ≥ 25 people per 1,000 sq ft | Use ventilation design occupancy to evaluate trigger | § 120.1(d)3 |
| System triggers (any one) | (A) air economizer; (B) modulating OA damper; (C) design OA > 3,000 cfm | If any system condition is true, DCV is required for qualifying spaces | § 120.1(d)3 |
| Minimum sensor coverage | ≥ 1 sensor per 10,000 sq ft, and at least one sensor in each qualifying room | Sensors drive OA modulation; any sensor reaching setpoint must trigger more ventilation for the zone | § 120.1(d)4A |
| Sensor mounting height | 3 ft–6 ft above floor (or occupant head height) | Placement required for representative CO2 measurement | § 120.1(d)4B and E 805.6.1.1(2) |
| CO2 control setpoint | ≤ 600 ppm + outdoor CO2 (or ≤ 1000 ppm when no outdoor sensor) | Controls must maintain these limits for sensor-equipped rooms | § 120.1(d)4C and E 805.6.2(4) |
| Sensor accuracy & calibration | ±75 ppm accuracy at 600 & 1000 ppm; factory calibrated; re-calibration interval not more frequent than 5 years | Manufacturer certification or field calibration required; failure must trigger minimum OA supply | § 120.1(d)4F and E 805.6.2(1) |
| Functional test standard | Test per NA7.5.5; CMC App. E provides detailed functional test steps (E 805.6) | Acceptance testing must verify modulation at/above and below setpoint and sensor wiring/location/calibration | § 120.5 / NA7.5.5 and E 805.6 |
Notes on code references: the district code text retrieved shows the DCV trigger wording at § 120.1(d)3 and the DCV device rules at § 120.1(d)4; the acceptance-testing requirement is in § 120.5 which calls out NA7.5.5, and Appendix E of the CMC contains E 805.6 (functional procedures and acceptance criteria) that implement the DCV test.
What testing must show (from E 805.6 / NA7.5.5)
- Construction inspection prior to functional testing: sensor calibration certificate or field calibration, proper sensor location (3–6 ft above floor), and DCV control setpoint at or below allowed concentration.
- Functional test steps required by E 805.6.1.2 (summary):
- Disable economizer (Step 1).
- Simulate CO2 at/just above setpoint — verify outdoor-air damper (single-zone) or OA/zone damper (multi-zone) opens to deliver the ventilation required in the certificate of compliance (Step 2).
- Simulate CO2 well below setpoint — verify damper modulates to the design minimum OA or reduced zone ventilation (Step 3).
- Restore economizer and remove overrides; then apply CO2 calibration gas at slightly above setpoint and verify OA damper modulates to deliver the certificate-of-compliance airflow (Step 5).
- Acceptance criteria include: sensor calibration and wiring, correct sensor location, setpoint limits (≤ 600 ppm + outdoor or ≤ 1000 ppm without outdoor sensor), minimum OA setting in occupied mode, a maximum OA damper position defined, and proper damper modulation above/below setpoint.
Exceptions & special cases
- The retrieved mechanical code lists several explicit exceptions to the DCV trigger: systems with exhaust-air energy recovery per the referenced section, multiple‑zone systems without DDC of individual zones communicating to a central panel, systems with design OA < 750 cfm, spaces where > 75% of design OA is makeup for exhausted/transfer air, and certain occupancies (e.g., correctional cells, daycare sickrooms, science labs, barber/beauty/nail salons, bowling alley seating). These are enumerated in the code DCV exceptions.
- Small spaces are excepted: spaces < 150 sq ft or a design occupancy < 10 people are excluded per the exception language.
- The Energy Code text in the retrieval also provides equivalent DCV provisions for multifamily sections (e.g., § 160.2 / § 160.3) with comparable thresholds and device rules; these are parallel requirements.
- Note on code numbering: the retrieved Energy Code excerpts show the DCV trigger at § 120.1(d)3 rather than at § 120.1(c)3. I did not find a file containing text labeled exactly § 120.1(c)3 in the provided materials; the applicable DCV trigger in the retrieved materials appears at § 120.1(d)3 (and equivalent multifamily provisions at § 160.2(c)5). If you specifically need the text of § 120.1(c)3 from another edition, that section text was not in the files provided.
Common mistakes (and how the test catches them)
- Installing CO2 sensors at the wrong height or location (not 3–6 ft / not in high-density area) — construction inspection and E 805.6 require and verify placement.
- Omitting sensor calibration or using an uncertified sensor — E 805.6 requires factory calibration or field calibration and accepts only specified accuracy (±75 ppm) and calibration intervals. Tests require calibration certificates or field calibration documentation.
- Forgetting to define a minimum occupied-mode OA or maximum OA damper position in control logic — E 805.6 acceptance criteria require a minimum OA setting and a maximum OA damper position be provided regardless of CO2 readings.
- Running economizer during the DCV functional test — the procedure explicitly requires economizer be disabled for the simulation steps, then restored. Failing to follow this invalidates the test.
- Assuming more sensors are not necessary: code requires no less than one sensor per 10,000 sq ft and at least one sensor in each qualifying room; larger zones may still require additional sensors to ensure representative readings.
Worked example — concrete scenario
Scenario: A conference room is 2,000 sq ft, design ventilation occupant density = 30 people per 1,000 sq ft, and the HVAC system serving the room has an air economizer.
Does DCV apply?
- Area is > 500 sq ft and occupant density is ≥ 25 / 1,000 sq ft and system has an air economizer → DCV is required per § 120.1(d)3.
How many CO2 sensors?
- Code requires CO2 sensors installed in each room that meets the criteria, with no less than one sensor per 10,000 sq ft. For a single 2,000 sq ft room, one CO2 sensor in the room satisfies the "per 10,000 sq ft" minimum and the "in each room" requirement. Place the sensor between 3–6 ft above the floor in the high‑density zone.
Setpoint to program:
- If outdoor CO2 is assumed 400 ppm, the interior setpoint must be ≤ 600 ppm + outdoor = ≤ 1,000 ppm, but the preferred implementation is to maintain ≤ 600 ppm + outdoor by using an outdoor CO2 sensor or the assumed default per the code. If no OSA sensor is installed, the allowable interior setpoint can be ≤ 1,000 ppm. Program controls accordingly.
What to expect at acceptance testing:
- Commissioning/test procedure per E 805.6: the tester disables the economizer; simulates CO2 slightly above the setpoint — verify OA damper opens to deliver the ventilation called for in the certificate of compliance; simulate CO2 well below setpoint — verify OA damper reduces to design minimum; restore economizer and, with controls restored, apply CO2 calibration gas above setpoint and verify OA damper modulates open to the certificate airflow. Tester documents sensor calibration, wiring, and placement as part of acceptance.
Related provisions (quick links)
- § 120.1(d)3 — DCV trigger (area / occupancy / system criteria).
- § 120.1(d)4 — DCV device requirements: sensor count, placement, setpoint behavior, outdoor CO2 determination.
- § 120.5 / NA7.5.5 — Required mechanical acceptance testing; DCV systems must be tested per NA7.5.5.
- E 805.6 (CMC Appendix E) — DCV functional test procedure and acceptance criteria (construction inspection, functional steps, acceptance criteria).
- E 503.4.6.9 — DCV statement in the mechanical appendix (exceptions and cross references).
- Multifamily equivalent: § 160.2(c)5 / § 160.3(d) — DCV rules mirrored for multifamily common areas.
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 46.45 High relevance — show source text
** Demand control ventilation (DCV) shall be required for spaces that are more than 500 square feet (46.45 m [2] ) and with a design occupancy for ventilation of not less than 25 people per 1000 square feet (92.9 m [2] ) of floor area and served by systems with one or more of the following: (1) Air-economizer. (2) Automatic modulating control of outdoor air damper. (3) Design outdoor airflow more than 3000 ft [3] /min (1.4158 m [3] /s). Exceptions: (1) Systems with exhaust air energy recovery in accordance with Section E 503.5.10.1.
(2) Multiple-zone systems without DDC of individual zones communicating with a central control panel. (3) Systems with a design outdoor airflow less than 750 ft [3] /min (0.3540 m [3] /s).
(4) Spaces where more than 75 percent of the space design outdoor airflow is required for makeup air that is exhausted from the space or transfer air that is required for makeup air that is exhausted from other spaces.
(5) Spaces with one of the following occupancy categories in accordance with Chapter 4 or ASHRAE 62.1: correctional cells, daycare sickrooms, science labs, barbers, beauty and nail salons, and bowling alley seating. [ASHRAE 90.1:6.4.3.8]
E 503.4.6.10 Outdoor Heating. Radiant heat systems shall be used to provide heat outdoors. Outdoor radiant heating systems shall be provided with controls that sense the presence of occupants or other device that automatically shuts down the system where no occupants are in the heating area.
E 503.4.6.11 Heated or Cooled Vestibules or Air Curtains with Integral Heating. Heating systems for vestibules and air curtain units with integral heating shall include automatic controls capable of and configured to shut off the heating system when outdoor air temperatures are more than 45°F (7.2°C). Vestibule heating and cooling systems shall be controlled by a thermostat in the vestibule capable of and configured to limit heating to a maximum of 60°F (15.5°C) and cooling to a minimum of 85°F (29.4°C).
Exception: Heating or cooling provided by siterecovered energy or by transfer air that would otherwise be exhausted. [ASHRAE 90.1:6.4.3.9]
E 503.4.6.11.1 Air Curtains. Air curtain unit performance shall be tested in accordance with ANSI/AMCA 220 and shall have a jet speed of not less than 6.6 feet per second (2.0 m/s) at 6 inches (152 mm) above the floor. Automatic controls shall be provided that will operate the air curtain unit with the opening and closing of the door and comply with Section E 503.4.6.11. To ensure proper operation, each air curtain unit shall be commissioned in accordance with the manufacturer’s instructions, including airstream split location and direction. [ASHRAE 90.1:10.4.5] E 503.4.6.12 Direct Digital Control (DDC) Requirements. Direct digital control shall be required in accordance with Section E 503.4.6.12.1 through Section E 503.4.6.12.3. [ASHRAE 90.1:6.4.3.10]
§ 5.1. High relevance — show source text
(a) Before an occupancy permit is granted, the following equipment and systems shall be certified as meeting the Acceptance Requirements for Code Compliance, as specified by the Reference Nonresidential Appendix NA7. A Certificate of Acceptance shall be submitted to the enforcement agency that certifies that the equipment and systems meet the acceptance requirements:
Outdoor air ventilation systems shall be tested in accordance with NA7.5.1.
Constant volume, single zone unitary air conditioning and heat pump unit controls shall be tested in accordance with NA7.5.2.
Duct systems that are subject to testing under Section 120.4(g)1, Section 141.0(b)2Di or Section 141.0(b)2Dii shall be tested in accordance with NA7.5.3.
Air economizers, DOAS, HRV or ERV systems shall be tested in accordance with NA7.5.4. Exception 1 to Section 120.5(a)4: Air economizers installed by the HVAC system manufacturer and certified to the Commission as being factory calibrated and tested are not required to comply with the Functional Testing section of the air economizer controls acceptance test as described in NA7.5.4.2. Exception 2 to Section 120.5(a)4: The DOAS, HRV, or ERV unit that does not meet the exhaust air heat recovery ratio as specified in Section 140.4(q)1 or does not include bypass or control to disable energy recovery as specified in Section 140.4(q)2.
Demand control ventilation systems required by Section 120.1(c)3 shall be tested in accordance with NA7.5.5.
Supply fan variable flow controls shall be tested in accordance with NA7.5.6.
Hydronic system variable flow controls shall be tested in accordance with NA7.5.7 and NA7.5.9.
Boiler or chillers that require isolation controls as specified by Section 140.4(k)2 or 140.4(k)3 shall be tested in accordance with NA7.5.7.
Hydronic systems with supply water temperature reset controls shall be tested in accordance with NA7.5.8.
Automatic demand shed controls shall be tested in accordance with NA7.5.10.
Fault Detection and Diagnostics (FDD) for Packaged Direct-Expansion Units shall be tested in accordance with NA7.5.11.
Automatic fault detection and diagnostics (FDD) for air handling units and zone terminal units shall be tested in accordance with NA7.5.12.
Distributed Energy Storage DX AC Systems shall be tested in accordance with NA7.5.13.
Thermal Energy Storage (TES) Systems shall be tested in accordance with NA7.5.14.
Supply air temperature reset controls shall be tested in accordance with NA7.5.15.
Water-cooled chillers served by cooling towers with condenser water reset controls shall be tested in accordance with NA7.5.16.
When an energy management control system is installed, it shall functionally meet all of the applicable requirements of Part 6.
Occupant sensing zone controls shall be tested in accordance with NA7.5.17.
Conductivity controls and overflow alarms for open and closed-circuit cooling towers shall be tested according to NA7.5.18.
§ 805.6 High relevance — show source text
(6) Where the economizer is disabled, the outdoor air damper closes to a minimum position; the return damper modulates 100 percent open, and mechanical cooling remains enabled. E 805.6 Demand-Controlled Ventilation Systems Acceptance (Form MECH-6A). The purpose of this test is to verify that systems required to employ demand-controlled ventilation shall be permitted to vary outside ventilation flow rates based on maintaining interior carbon dioxide (CO 2 ) concentration setpoints. Demand-controlled ventilation refers to an HVAC system’s ability to reduce outdoor air ventilation flow below design values where the space served is at less than design occupancy. Carbon dioxide is a good indicator of occupancy load and is the basis used for modulating ventilation flow rates.
E 805.6.1 Test Procedure. The procedure for performing a functional test for demand-control ventilation (DVC) systems shall be in accordance with Section E 805.6.1.1 and Section E 805.6.1.2.
E 805.6.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Carbon dioxide control sensor is factory calibrated or field-calibrated in accordance with this appendix.
(2) The sensor is located in the high-density space between 3 feet (914 mm) and 6 feet (1829 mm) above the floor or at the anticipated level of the occupants’ heads.
(3) DCV control setpoint is at or below the carbon dioxide concentration permitted by this appendix.
E 805.6.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable economizer controls.
Step 2: Simulate a signal at or slightly above the carbon dioxide concentration setpoint required by this appendix. Verify and document the following:
(1) For single zone units, outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
(2) For multiple zone units, either outdoor air damper or zone damper modulate open to satisfy the zone ventilation requirements.
Step 3: Simulate signal well below the carbon dioxide setpoint. Verify and document the following:
(1) For single zone units, outdoor air damper modulates to the design minimum value.
(2) For multiple zone units, either outdoor air damper or zone damper modulate to satisfy the reduced zone ventilation requirements.
Step 4: Restore economizer controls and remove system overrides initiated during the test.
Step 5: With controls restored, apply carbon dioxide calibration gas at a concentration slightly above the setpoint to the sensor. Verify that the outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
E 805.6.2 Acceptance Criteria. Demand-controlled ventilation systems acceptance criteria shall be as follows:
(1) Each carbon dioxide sensor is factory calibrated (with calibration certificate) or field calibrated.
(2) Each carbon dioxide sensor is wired correctly to the controls to ensure proper control of the outdoor air damper.
(3) Each carbon dioxide sensor is located correctly within the space 1 foot (305 mm) to 6 feet (1829 mm) above the floor.
(4) Interior carbon dioxide concentration setpoint is not more than 600 parts per million (ppm) plus outdoor air carbon dioxide value where dynamically measured or not more than 1000 ppm where no OSA sensor is provided.
§ 120.1 High relevance — show source text
- 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.
- 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.
- 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.
70 2025 CALIFORNIA ENERGY CODE
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NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS
§ 4.420 High relevance — show source text
410|≥4.420|NA|AHRI
550/590| |Water
source
electri-
cally
operated
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displace-
ment|<75|≤0.7885
FL
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IPLV.IP|≤0.7875
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IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
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cally
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ment|≥75
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<150|≤0.7579
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IPLV.IP|≤0.7140
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IPLV.IP|54/445|≥4.640|≥3.680|≥2.680|NA|≥8.330|≥6.410|≥4.420|NA|NA| |Water
source
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ment|≥75
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<150|≤0.7579
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≤0.5895
IPLV.IP|≤0.7140
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IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
source
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cally
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ment|≥150
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≤0.5684
IPLV.IP|≤0.7140
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IPLV.IP|54/445|≥4.640|≥3.680|≥2.680|NA|≥8.330|≥6.410|≥4.420|NA|NA| |Water
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IPLV.IP|75/655|NA|NA|NA|≥3.550|NA|NA|NA|6.150|6.150| |Water
source
electri-
cally
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displace-
ment|≥300
and
<600|≤0.6421
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≤0.5474
IPLV.IP|≤0.6563
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≤0.4305
IPLV.IP|54/445|≥4.930|≥3.960|≥2.970|NA|≥8.900|≥6.§ 180.2 High relevance — show source text
2(c)2, 4, 180.2(b)2A Tower 110.2(e), 120.5(a)16, 120.6(a)4, 8, 120.6(b)1, 120.6(b)5, Table 130.5B, 140.4(b)3, 140.4(h), 160.3(d)1P, 170.2(c)2C, 170.2(c)4F
2025 CALIFORNIA ENERGY CODE 303
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
INDEX
Daylit Zone 130.1(d), 130.1(f), 140.3(c)1A, 140.6(a)2, 140.6(a)3, Table 140.6-A, 160.5(b)4D, F, 170.2(e)2B, Table 170.2-L DDC Applications and Qualifications Table 120.2-A, Table 160.3-C Dead Band 120.2(b)3, 140.4(k)7 Dead Band Flow Rate 140.4(d) Decibel Level 110.9(b)6 Decorative Gas Appliance 110.2(c), 140.6(b)4, 150.0(e), 160.1(f) Dedicated Electrical Receptacle 150.0(n)1A, 160.4 Dedicated Outdoor Air Systems (DOAS) 140.4(p), 170.2(c)4N Dedicated Raceway 150.0(s) Default Fenestration
Product U-Factors Table 110.6-A
Default Solar Heat Gain Coefficient (SHGC) Table 110.6-B, 10-111(a)1B, 110.6(a)3 Default U-Factor 10-111(a)1B, 10-111(b)1B, 10-112(a), 110.6(a)2 Default Values 10-112(a), Table 140.4-D, 150.1(c)3, 170.2(a)3A, Table 170.2-E Default Values for Fan KWdesign Based on Motor Nameplate HP Table 140.4-D, Table 170.2-E-1 Dehumidification Table 110.2-K, 120.6(h), 140.4(b)2A, 140.4(e)1, 141.1(c)1, 170.2(c)2B, 170.2(c)4C Demand Control ventilation (DCV) 120.1(d), 120.5(a)5, 160.2(c)5, 160.3(d)1 Demand-controlled local ventilation exhaust airflow rates and capture efficiency Table 150.0-E, Table 160.2-E
Demand-controlled mechanical exhaust 150.0(o), 160.2(b)2A Flexibility 150.1(b)1 Management 110.12 Recirculation 150.1(c)8, 150.2(b)1H, 170.2(d), 180.2(b)3B Response signal 110.10(b)1A, 110.10(b)1B, 110.12(a-e), 140.6(a)2, 170.2(e)2B Responsive controls 110.10(b)1A,
§ 5.3 High relevance — show source text
(g) Duct sealing. Duct systems shall comply with Subsection 1 or 2 below:
- New duct systems that meet the criteria in Subsections A, B, C and D below shall be sealed to a leakage rate not to exceed 6 percent of the nominal air handler airflow rate as confirmed through acceptance testing, in accordance with Reference Nonresidential Appendix NA7.5.3; A. The duct system does not serve a healthcare facility; and B. The duct system provides conditioned air to an occupiable space for a constant volume, single zone, space-conditioning system; and C. The space-conditioning system serves less than 5,000 square feet of conditioned floor area; and D. The combined surface area of the ducts located outdoors or in unconditioned space is more than 25 percent of the total surface area of the entire duct system.
- New duct systems that are not subject to testing under Section 120.4(g)1 shall instead meet the duct leakage testing requirements of CMC Section 603.9.2.
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, 25402.8, and 25943, Public Resources Code.
SECTION 120.5—REQUIRED NONRESIDENTIAL MECHANICAL SYSTEM ACCEPTANCE
Nonresidential and hotel/motel buildings shall comply with the applicable requirements of Sections 120.5(a) through 120.5(b).
Exception to Section 120.5: Systems serving healthcare facilities.
(a) Before an occupancy permit is granted, the following equipment and systems shall be certified as meeting the Acceptance Requirements for Code Compliance, as specified by the Reference Nonresidential Appendix NA7. A Certificate of Acceptance shall be submitted to the enforcement agency that certifies that the equipment and systems meet the acceptance requirements:
Outdoor air ventilation systems shall be tested in accordance with NA7.5.1.
Constant volume, single zone unitary air conditioning and heat pump unit controls shall be tested in accordance with NA7.5.2.
Duct systems that are subject to testing under Section 120.4(g)1, Section 141.0(b)2Di or Section 141.0(b)2Dii shall be tested in accordance with NA7.5.3.
Air economizers, DOAS, HRV or ERV systems shall be tested in accordance with NA7.5.4. Exception 1 to Section 120.5(a)4: Air economizers installed by the HVAC system manufacturer and certified to the Commission as being factory calibrated and tested are not required to comply with the Functional Testing section of the air economizer controls acceptance test as described in NA7.5.4.2. Exception 2 to Section 120.5(a)4: The DOAS, HRV, or ERV unit that does not meet the exhaust air heat recovery ratio as specified in Section 140.4(q)1 or does not include bypass or control to disable energy recovery as specified in Section 140.4(q)2.
Demand control ventilation systems required by Section 120.1(c)3 shall be tested in accordance with NA7.5.5.
Supply fan variable flow controls shall be tested in accordance with NA7.5.6.
§ 805.5.2 High relevance — show source text
Step 3: Disable the economizer and simulate a cooling demand. Verify and document the following:
(1) Economizer damper shall close to its minimum position.
(2) Applicable fans and dampers shall operate as intended to maintain building pressure.
(3) The unit heating is disabled.
Step 4: Simulate a heating demand, and set the economizer so that it is capable of operating (e.g., actual outdoor air conditions are below lockout setpoint). Verify the economizer is at minimum position.
Step 5: Restore demand control ventilation systems (where applicable) and remove system overrides initiated during the test.
E 805.5.2 Acceptance Criteria. Air economizer controls acceptance criteria shall be as follows:
484 2025 CALIFORNIA MECHANICAL CODE
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APPENDIX E
(1) Where the economizer is factory installed and certified, a valid factory certificate is required for acceptance. No additional equipment tests are necessary.
(2) Air economizer lockout setpoint is in accordance with this appendix. Outside sensor location accurately reads true outdoor air temperature and is not affected by exhaust air or other heat sources.
(3) Sensors are located to achieve the desired control.
(4) During economizer mode, the outdoor air damper shall modulate open to a maximum position and return air damper to 100 percent closed.
(5) The outdoor air damper is 100 percent open before mechanical cooling is enabled and for units 75 000 Btu/h (22 kw) and larger remains at 100 percent open while mechanical cooling is enabled (economizer integration where used for compliance).
(6) Where the economizer is disabled, the outdoor air damper closes to a minimum position; the return damper modulates 100 percent open, and mechanical cooling remains enabled. E 805.6 Demand-Controlled Ventilation Systems Acceptance (Form MECH-6A). The purpose of this test is to verify that systems required to employ demand-controlled ventilation shall be permitted to vary outside ventilation flow rates based on maintaining interior carbon dioxide (CO 2 ) concentration setpoints. Demand-controlled ventilation refers to an HVAC system’s ability to reduce outdoor air ventilation flow below design values where the space served is at less than design occupancy. Carbon dioxide is a good indicator of occupancy load and is the basis used for modulating ventilation flow rates.
E 805.6.1 Test Procedure. The procedure for performing a functional test for demand-control ventilation (DVC) systems shall be in accordance with Section E 805.6.1.1 and Section E 805.6.1.2.
E 805.6.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Carbon dioxide control sensor is factory calibrated or field-calibrated in accordance with this appendix.
(2) The sensor is located in the high-density space between 3 feet (914 mm) and 6 feet (1829 mm) above the floor or at the anticipated level of the occupants’ heads.
(3) DCV control setpoint is at or below the carbon dioxide concentration permitted by this appendix.
E 805.6.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable economizer controls.
§ 805.6.2 High relevance — show source text
Step 2: Simulate a signal at or slightly above the carbon dioxide concentration setpoint required by this appendix. Verify and document the following:
(1) For single zone units, outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
(2) For multiple zone units, either outdoor air damper or zone damper modulate open to satisfy the zone ventilation requirements.
Step 3: Simulate signal well below the carbon dioxide setpoint. Verify and document the following:
(1) For single zone units, outdoor air damper modulates to the design minimum value.
(2) For multiple zone units, either outdoor air damper or zone damper modulate to satisfy the reduced zone ventilation requirements.
Step 4: Restore economizer controls and remove system overrides initiated during the test.
Step 5: With controls restored, apply carbon dioxide calibration gas at a concentration slightly above the setpoint to the sensor. Verify that the outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
E 805.6.2 Acceptance Criteria. Demand-controlled ventilation systems acceptance criteria shall be as follows:
(1) Each carbon dioxide sensor is factory calibrated (with calibration certificate) or field calibrated.
(2) Each carbon dioxide sensor is wired correctly to the controls to ensure proper control of the outdoor air damper.
(3) Each carbon dioxide sensor is located correctly within the space 1 foot (305 mm) to 6 feet (1829 mm) above the floor.
(4) Interior carbon dioxide concentration setpoint is not more than 600 parts per million (ppm) plus outdoor air carbon dioxide value where dynamically measured or not more than 1000 ppm where no OSA sensor is provided.
(5) A minimum OSA setting is provided where the system is in occupied mode in accordance with this appendix regardless of space carbon dioxide readings.
(6) A maximum OSA damper position for DCV control shall be established in accordance with this appendix, regardless of space carbon dioxide readings.
(7) The outdoor air damper shall modulate open where the carbon dioxide concentration within the space exceeds setpoint.
(8) The outdoor air damper modulates closed (toward minimum position) where the carbon dioxide concentration within the space is below setpoint.
E 805.7 Supply Fan Variable Flow Controls (Form MECH-7A). The purpose of this test is to ensure that the supply fan in a variable air volume application modulates to meet system airflow demand. In most applications, the individual VAV boxes serving each space will modulate the amount of
2025 CALIFORNIA MECHANICAL CODE 485
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APPENDIX E
air delivered to the space based on heating and cooling requirements. As a result, the total supply airflow provided by the central air handling unit shall vary to maintain sufficient airflow through each VAV box. Airflow shall be controlled using a variable frequency drive (VFD) to modulate supply fan speed and vary system airflow. The most common strategy for controlling the VFD is to measure and maintain static pressure within the duct.
E 805.7.1 Test Procedure. The procedure for performing a functional test for supply fan variable controls shall be in accordance with Section E 805.7.1.1 and Sec tion E 805.7.1.2.
§ 90.1 High relevance — show source text
[ASHRAE 90.1:6.4.3.6.2]
E 503.4.6.7.3 Control Interlock. Where a zone is served by a system or systems with both humidification and dehumidification capability, means (such as limit switches, mechanical stops, or, for DDC systems, software programming) shall be provided capable of and configured to prevent simultaneous operation of humidification and dehumidification equipment. Exception: Systems serving zones where humidity levels are required to be maintained with precision of not more than ± 5 percent relative humidity to comply with applicable codes or accreditation standards or as approved by the Authority Having Jurisdiction. [ASHRAE 90.1:6.4.3.6.3]
E 503.4.6.8 Freeze Protection and Snow or Ice Melting Systems. Freeze protection systems, such as heat tracing of outdoor piping and heat exchangers, including self-regulating heat tracing, shall include automatic controls capable of and configured to shut off the systems when outdoor air temperatures are more than 40°F (4°C) or when the conditions of the protected fluid will prevent freezing. Snow and ice melting systems shall include automatic controls capable of and configured to shut off the systems when the pavement temperature is more than 50°F (10°C) and no precipitation is falling, and an automatic or manual control that will allow shutoff when the outdoor temperature is more than 40°F (4°C) so that the potential for snow or ice accumulation is negligible. [ASHRAE 90.1:6.4.3.7] E 503.4.6.9 Ventilation Controls for High- Occupancy Areas. Demand control ventilation (DCV) shall be required for spaces that are more than 500 square feet (46.45 m [2] ) and with a design occupancy for ventilation of not less than 25 people per 1000 square feet (92.9 m [2] ) of floor area and served by systems with one or more of the following: (1) Air-economizer. (2) Automatic modulating control of outdoor air damper. (3) Design outdoor airflow more than 3000 ft [3] /min (1.4158 m [3] /s). Exceptions: (1) Systems with exhaust air energy recovery in accordance with Section E 503.5.10.1.
(2) Multiple-zone systems without DDC of individual zones communicating with a central control panel. (3) Systems with a design outdoor airflow less than 750 ft [3] /min (0.3540 m [3] /s).
(4) Spaces where more than 75 percent of the space design outdoor airflow is required for makeup air that is exhausted from the space or transfer air that is required for makeup air that is exhausted from other spaces.
(5) Spaces with one of the following occupancy categories in accordance with Chapter 4 or ASHRAE 62.1: correctional cells, daycare sickrooms, science labs, barbers, beauty and nail salons, and bowling alley seating. [ASHRAE 90.1:6.4.3.8]
E 503.4.6.10 Outdoor Heating. Radiant heat systems shall be used to provide heat outdoors. Outdoor radiant heating systems shall be provided with controls that sense the presence of occupants or other device that automatically shuts down the system where no occupants are in the heating area.
§ 301.1.2 High relevance — show source text
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .J 301.1.2
Demand Control Ventilation (DCV) . . . . . . . . . . .J 301.0
Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .J 201.1.1
CLEARANCES FOR
Air-conditioning appliances,
gas type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903.2.4
Air heaters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914.4
Appliances . . . . . . . . . . . . . . . . . 303.3, 303.8, 303.8.4,
303.8.4.1, 303.10, 304.1,
303.10.1, 304.3.1.1, 516.2.1,
701.6.2, Table 303.10.1
Boilers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 303.2, 904.3,
1010.0, Table 904.3.2
Broilers units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921.2
Clothes dryers, gas type . . . . . . . . . . . . . . . . . . 908.3.1
Connectors. . . . . . . . . . . . . . . 802.10.4, Table 303.10.1,
Table 802.7.3.3
Cooking appliances. . . . . . . . 919.4.1, 919.4.2, 919.5.2,
Draft hoods and controls . . . . . . . . . . . . . . . . . 802.12.6
Ducts, commercial kitchen
exhaust . . . . . . . . . . . . . .303.10.1.1, 507.4, 507.4.2.3,
507.4.6.3, 510.7.3,
510.9.1, 510.9.2
Ducts, furnaces. . . . . . . . . . . . . . . . . . . . . . . . . . . 905.2
Ducts, product conveying,
exhaust. . . . . . . . . . . . . . . . . . . . . 303.10.1.2, 506.10,
Equipment on roofs . . . . . . . . . . . . . . . . 303.8, 303.8.4,
303.8.4.1, 304.2, 304.3.1.1
Fans, commercial
kitchen exhaust . . . . . . . . . . . . . . . . . . . . . . . . 510.7.3
Floor furnace . . . . . . . . . . . . . . . . . . . . . . 906.8, 906.12
§ 120.1 High relevance — show source text
- 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.
70 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS
E. 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 120.1-F for each space with a CO 2 sensor(s), plus the greater of either the exhaust air rate or the rate required by Section 120.1(c)3 for other spaces served by the system. F. CO 2 sensors shall be certified by the manufacturer to be accurate within plus or minus 75 ppm at a 600 and 1000 ppm concentration when measured at sea level and 25°C, factory calibrated and certified by the manufacturer to require calibration no more frequently than once every 5 years. Upon detection of sensor failure, the system shall provide a signal which resets to supply the minimum quantity of outside air to levels required by Section 120.1(c)3 to the zone serviced by the sensor at all times that the zone is occupied. G. The CO 2 sensor(s) reading for each zone shall be displayed continuously, and shall be recorded on systems with DDC to the zone level.
- Occupied-standby zone controls. A. Space conditioning zones shall include occupied standby controls complying with Section 120.1(d)5B when all of the following are true: i. All rooms served by the zone are permitted to have their ventilation air reduced to zero while in occupiedstandby mode per Table 120.1-A; and ii. Occupant sensors are required by Sections 130.1(c)5 and 6; and iii. The zone and ventilation system is not served by pneumatic controls. B. Occupied-standby zone controls shall comply with the following: i. Occupant sensors shall have suitable coverage and placement to detect occupants in the entire space. In 20 minutes or less after no occupancy is detected by any sensors covering the room, occupant sensing controls shall indicate a room is vacant.
ii.
Frequently asked questions
Do I always need an outdoor CO2 sensor for DCV?
No. The code allows you to assume outdoor CO2 = 400 ppm if you do not dynamically measure outdoor CO2; however, if you install an outdoor CO2 sensor within 4 ft of the intake, the control may use a measured outdoor value and the interior setpoint must be ≤ 600 ppm + measured outdoor. § 120.1(d)4D and E 805.6 describe this.
How many sensors do I need for one large open-plan zone?
You must have at least one CO2 sensor per qualifying room, and no fewer than one sensor per 10,000 sq ft. For open-plan areas treated as a single "room," use this rule to determine minimum sensors—but add sensors where needed to get representative readings for high‑density areas. § 120.1(d)4A.
What CO2 setpoint is acceptable at acceptance testing?
Interior CO2 setpoint must be no more than 600 ppm + outdoor CO2 when outdoor CO2 is dynamically measured, or no more than 1000 ppm if no outdoor sensor is provided. See E 805.6.2(4) and § 120.1(d)4C.
What if the system has an exhaust‑air energy recovery device?
Systems with exhaust-air energy recovery that meet the referenced provisions are listed as an exception to the DCV trigger; check the specific exception text (Appendix/Section references) to confirm applicability. The retrieved materials list that exception.
Who signs off on DCV acceptance testing?
Per § 120.5, a Certificate of Acceptance must be submitted to the enforcement agency certifying the required acceptance tests (NA7) were performed — DCV tests are covered under NA7.5.5 as noted in § 120.5.
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