Title 24 · California Energy Code
Design & control requirements to maintain minimum outside-air ventilation rates
Homes and apartments must have ventilation systems designed and controlled to reliably deliver the code minimum outside air. The rules require dampers/ducts and active (dynamic) controls — not fixed stops — so VAV systems can hold outside‑air within ±10% of the design rate; multifamily units have parallel controls and whole‑dwelling ventilation equations. If CO2 sensors are used for demand control, the code sets sensor placement, accuracy, setpoints, and fail‑safe behavior; systems must be tested and documented at acceptance.
Last reviewed: July 6, 2026
What the code requires — plain English
The California Energy Code requires HVAC systems be designed and controlled so the minimum outside‑air ventilation rate can be delivered and held reliably. Variable‑air‑volume (VAV) systems must include dynamic controls that keep measured outside air within ±10% of the design minimum at full and reduced airflow; constant‑volume systems must also be within ±10% of the required rate when measured. These control, duct/damper design, and acceptance‑test requirements are set out in § 120.1(f) for nonresidential systems and the parallel multifamily requirements in § 160.2(c) (see citations) — I could not find § 120.4(f) in the provided files, so this guidance is grounded in the retrieved sections instead.
The single most important rule: design ducting/dampers/controls so the system can supply the design minimum outside air, and provide controls that actively regulate that outside‑air flow so measured ventilation is within ±10% of the design value.
Requirements in detail
1) Design envelope — ductwork, dampers, controls
- Systems must be physically capable of operating at the design minimum outside‑air rate (or the makeup rate required for exhaust) by providing appropriate ductwork, motorized dampers, and controls. See § 120.1(f)1 and the matching multifamily language § 160.2(c)7.A.
2) Dynamic controls for VAV systems
- Variable air volume (VAV) systems must include dynamic controls (not a fixed minimum damper stop) that are capable of maintaining measured outdoor‑air ventilation rates within ±10% of the design minimum at both full and reduced supply airflow conditions. Fixed minimum damper position alone is explicitly not permitted as the dynamic control strategy. See § 120.1(f)2 and § 160.2(c)7.B.
3) Constant‑volume systems and testing
- Measured outdoor‑air rates for constant‑volume systems must be within ±10% of the required outside‑air rate at acceptance/test. All mechanical ventilation and space‑conditioning systems must be tested to confirm they can operate within this tolerance. See § 120.1(f)3 and § 160.2(c)7.C.
4) Demand Control Ventilation (DCV) / CO2-based control
- Where DCV is required/used, the code requires:
- CO2 sensors in each qualifying room (minimum density: 1 sensor per 10,000 ft²) and location between 3 ft and 6 ft above the floor (or occupant head height).
- DCV control shall maintain interior CO2 ≤ 600 ppm + outdoor CO2 (or use alternative prescribed limits); the outdoor CO2 may be assumed 400 ppm or dynamically measured at the outdoor intake. If a sensor fails, controls must revert to supplying the design minimum outside air. See § 120.1(d)4 and § 160.2(c)5D.
- CO2 sensors must be manufacturer‑certified for accuracy ±75 ppm at 600 and 1000 ppm, factory calibrated, and require calibration no more often than every 5 years.
Decision‑relevant dimensions/values
| Decision / value | Required value or threshold | Code reference |
|---|---|---|
| VAV dynamic control tolerance | ±10% of design minimum outdoor air | § 120.1(f)2 — |
| Constant‑volume measured tolerance | ±10% of required outdoor air | § 120.1(f)3 / § 160.2(c)7.C — |
| System design capability | Dampers/ducts/controls to operate at min outside air or makeup rate | § 120.1(f)1 / § 160.2(c)7.A — |
| CO2 sensor setpoint (DCV) | ≤ 600 ppm + outdoor CO2 | § 120.1(d)4C / § 160.2(c)5D(iii) — |
| CO2 sensor location | 3–6 ft above floor or occupant head height | § 120.1(d)4B / § 160.2(c)5D(ii) — |
| CO2 sensor accuracy & calibration | ±75 ppm accuracy at 600 & 1000 ppm; calibration interval ≤ 5 years | § 120.1(d)4F / § 160.2(c)5D(vi) — |
| Multifamily whole‑dwelling ventilation | Qtot = 0.03 Afloor + 7.5(Nbr + 1) (cfm) | Equation 160.2‑B — § 160.2(b)(iv) — |
| Multifamily CFI damper control | Motorized outdoor‑air damper must be closed when ventilation not required; open when required | § 160.2(b)2A.ii–c — |
Exceptions & special cases
- Fixed minimum damper stops are explicitly not allowed as the VAV control strategy — the code requires active/dynamic modulation § 120.1(f)2.
- DCV does not allow the system to deliver more than the design outdoor‑air ventilation rate even if CO2 exceeds setpoint (there is an exception that the outdoor air ventilation rate need not be larger than the design rate) — see § 120.1(d)4C and § 160.2(c)5D(iii).
- Multifamily Central Fan Integrated (CFI) systems: central fan must not be used continuously as the approved whole‑dwelling ventilation strategy unless specifically approved; motorized dampers must prevent all airflow into the space‑conditioning ducts when closed. See § 160.2(b)2A and related subsections.
- If CO2 sensors fail, the control must default to supplying the minimum outdoor air required by the applicable design section (e.g., § 120.1(c)3 or § 160.2(c)3).
Common mistakes
- Relying on a fixed minimum damper stop instead of an active control algorithm (not permitted for VAV). Don’t treat a fixed mechanical stop as “dynamic control.” § 120.1(f)2.
- Skipping the acceptance test that verifies measured outdoor air is within ±10% — the code requires testing to confirm compliance. § 120.1(f)3 / § 160.2(c)7.C.
- Installing CO2 sensors in the wrong location (too high, too close to supply, or outside the 3–6 ft height band) or failing to meet the sensor density requirement for DCV. § 120.1(d)4B / § 160.2(c)5D(i–ii).
- Forgetting the fail‑safe: controls must default to minimum design outdoor air if sensors fail; omission of fail‑safe violates § 120.1(d)4F / § 160.2(c)5D(vi).
- Using a building’s central fan continuously in multifamily CFI systems without the required motorized damper and damper control sequencing. § 160.2(b)2A.
Worked example — single‑zone VAV serving an office suite
Scenario:
- Design minimum outdoor air for zone = 1,200 cfm (calculated per Equation 120.1‑F / 160.2‑H).
- System is VAV and has reduced supply airflow mode (e.g., night‑economy or part‑load).
Steps to comply:
- Design: provide ductwork and a modulating outdoor‑air damper and controls sized so the unit can deliver at least 1,200 cfm OSA (or makeup needed for exhaust), per § 120.1(f)1.
- Controls: implement an active control algorithm that senses supply flow and outdoor‑air fraction (or uses an outdoor‑air flow sensor or equivalent) and modulates the outside‑air damper so measured outside air tracks the design minimum. Do not rely on a fixed damper stop. This satisfies § 120.1(f)2.
- Tolerance: the control must maintain measured OSA between 1,080 cfm and 1,320 cfm (±10% of 1,200 cfm) at full and reduced supply flow conditions. Verify both conditions. § 120.1(f)2–3.
- Commissioning/test: perform an acceptance test that measures outdoor‑air flow at full and reduced airflows and document the readings are within ±10% — if not, adjust control strategy or damper linkage. § 120.1(f)3.
If DCV is used instead (e.g., for a high‑density conference room), ensure CO2 sensors meet the 1 per 10,000 ft² rule, are located 3–6 ft high, certified ±75 ppm, and that the control maintains CO2 ≤ 600 ppm + outdoor CO2 or reverts to the design OSA minimum on sensor failure (see § 120.1(d)4).
Related provisions (quick links)
- § 120.1(c)3 — Zone outdoor‑air rate calculation (Equation 120.1‑F) and minimum ventilation rates.
- § 120.1(d)4 — Demand control ventilation device requirements (CO2 sensor placement, setpoints, fail‑safe, calibration).
- § 160.2(c)3 — Multifamily zone ventilation rate calculation (Equation 160.2‑H) and required rates.
- § 160.2(c)5D — Multifamily DCV device requirements (mirrors nonresidential DCV rules).
- Equation 160.2‑B — Whole‑dwelling ventilation equation for multifamily units.
Note: The user asked for § 120.4(f) as a controlling section. I searched the files you provided and did not find text labeled § 120.4(f); the detailed "design and control requirements for quantities of outdoor air" are present in § 120.1(f) in the retrieved documents and the multifamily parallel in § 160.2(c) — the article above is grounded in those retrieved sections.
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 120.1 High relevance — show source text
**
- All mechanical ventilation and space-conditioning systems shall be designed with and have installed ductwork, dampers and controls that allow design minimum outside air rates to be operated at no less than the larger of (1) the minimum levels specified in Section 120.1(c)3; or (2) the rate required for make-up of exhaust systems that are required for a covered or noncovered process, for control of odors, or for the removal of contaminants within the space.
- All variable air volume mechanical ventilation and space-conditioning systems shall include dynamic controls that are capable of maintaining measured outside air ventilation rates within 10 percent of the design minimum 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.
- All mechanical ventilation and space-conditioning systems shall be tested to confirm their ability to operate within 10 percent of the design minimum outside air rate.
(g) Air classification and recirculation limitations. Air classification and recirculation limitations of air shall be based on the air classification as listed in Table 120.1-A or Table 120.1-C, and in accordance with the requirements of Sections 120.1(g)1 through 4.
Note: Air class definitions are taken directly from ASHRAE 62.1 and are duplicated here for convenience.
- 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]
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- Class 2 Air is air with moderate contaminant concentration, mild sensory-irritation intensity or mildly offensive odors (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 120.1(g)2A through 120.1(g)2E: A. Recirculation of Class 2 air within the space of origin shall be permitted [ASHRAE 62.1:5.13.3.2.1]; B. Recirculation or transfer of Class 2 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 C. Transfer of Class 2 air to toilet rooms [ASHRAE 62.1:5.13.3.2.3]; or
D. Recirculation or transfer of Class 2 air to Class 4 spaces [ASHRAE 62.1:5.13.3.2.4]; or E. Class 2 air shall not be recirculated or transferred to Class 1 spaces. [ASHRAE 62.1:5.13.3.2.5] Exception to Section 120.1(g)2E: When using any energy recovery device, recirculation from leakage, carryover, or transfer from the exhaust side of the energy recovery device is permitted.
§ 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.
§ 120.1 High relevance — show source text
iii. When a single zone serves multiple spaces, there shall be an occupant sensor in each space and the zone shall not be considered vacant until all spaces in the zone are vacant. iv. One hour prior to normal scheduled occupancy, the occupant sensor ventilation control shall allow preoccupancy purge as described in Section 120.1(d)2. v. When the zone is scheduled to be occupied and occupant sensing controls in all spaces served by the zone indicate the spaces are unoccupied, the zone shall be placed in occupied-standby mode. vi. In 5 minutes or less after entering occupied-standby mode, mechanical ventilation to the zone shall be shut off until the space becomes occupied or until ventilation is needed to provide space heating or conditioning. When mechanical ventilation is shut off to the zone, the ventilation system serving the zone shall reduce the system outside air rate by the amount of outside air required for the zone. vii. Where the system providing space conditioning also provides ventilation to the zone, in 5 minutes or less after entering occupied-standby mode, space-conditioning zone setpoints shall be reset in accordance with Section 120.2(e)3.
(e) Ducting for zonal heating and cooling units. Where a return plenum is used to distribute outdoor air to a zonal heating or cooling unit, which then supplies the air to a space in order to meet the requirements of Section 120.1(c)3, the outdoor air shall be ducted to discharge either:
Within 5 feet of the unit; or
Within 15 feet of the unit, substantially toward the unit, and at a velocity not less than 500 feet per minute.
(f) Design and control requirements for quantities of outdoor air.
- All mechanical ventilation and space-conditioning systems shall be designed with and have installed ductwork, dampers and controls that allow design minimum outside air rates to be operated at no less than the larger of (1) the minimum levels specified in Section 120.1(c)3; or (2) the rate required for make-up of exhaust systems that are required for a covered or noncovered process, for control of odors, or for the removal of contaminants within the space.
- All variable air volume mechanical ventilation and space-conditioning systems shall include dynamic controls that are capable of maintaining measured outside air ventilation rates within 10 percent of the design minimum 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.
- All mechanical ventilation and space-conditioning systems shall be tested to confirm their ability to operate within 10 percent of the design minimum outside air rate.
(g) Air classification and recirculation limitations. Air classification and recirculation limitations of air shall be based on the air classification as listed in Table 120.1-A or Table 120.1-C, and in accordance with the requirements of Sections 120.1(g)1 through 4.
Note: Air class definitions are taken directly from ASHRAE 62.1 and are duplicated here for convenience.
- 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]
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§ 160.2 High relevance — show source text
c. When a single zone damper or a single zone system serves multiple spaces, there shall be an occupant sensor in each space and the zone shall not be considered vacant until all spaces in the zone are vacant. d. One hour prior to normal scheduled occupancy, the occupant sensor ventilation control shall allow preoccupancy purge as described in Section 160.2(c)5B. e. When the zone is scheduled to be occupied and occupant sensing controls in all spaces served by the zone indicate the spaces are unoccupied, the zone shall be placed in occupied-standby mode. f. In 5 minutes or less after entering occupied-standby mode, mechanical ventilation to the zone shall be shut off until the space becomes occupied or until ventilation is needed to provide space heating or conditioning. When mechanical ventilation is shut off to the zone, the ventilation system serving the zone shall reduce the system outside air rate by the amount of outside air required for the zone. g. Where the system providing space conditioning also provides ventilation to the zone, in 5 minutes or less after entering occupied-standby mode, space-conditioning zone setpoints shall be reset in accordance with Section 120.2(e)3. 6. Ducting for zonal heating and cooling units. Where a return plenum is used to distribute outdoor air to a zonal heating or cooling unit that then supplies the air to a space in order to meet the requirements of Section 160.2(c)3, the outdoor air shall be ducted to discharge either: A. Within 5 feet of the unit; or
B. Within 15 feet of the unit, substantially toward the unit and at a velocity not less than 500 feet per minute. 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).
§ 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.
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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.
§ 503.5.11.3 High relevance — show source text
A + B - ( E/M ) ≥ 50% (Equation E 503.5.11.3)
Where:
A = Percentage that the exhaust and makeup airflow rates are capable of being reduced from design conditions.
B = Sensible energy recovery ratio.
E = Exhaust airflow rate through the heat recovery device at design conditions.
M = Makeup airflow rate of the system at design conditions.
(2) VAV laboratory exhaust and room supply systems that are required to have minimum circulation rates to be in accordance with the codes or
accreditation standards shall be capable of and configured to reduce zone exhaust and makeup airflow rates to the regulated minimum circulation values, or the minimum required to maintain pressurization relationship requirements. Systems serving nonregulated zones shall be capable of and configured to reduce exhaust and makeup airflow rates to 50 percent of the zone design values, or the minimum required to maintain pressurization relationship requirements.
(3) Direct makeup (auxiliary) air supply of 75 percent or more of the exhaust airflow rate, heated not more than 2°F (1°C) below room setpoint, cooled to not less than 3°F (2°C) above room setpoint, no humidification added, and no simultaneous heating and cooling are used for dehumidification control. [ASHRAE 90.1:6.5.7.3]
E 503.5.12 Radiant Heating Systems. Radiant heating systems shall be in accordance with Section E 503.5.12.1 through Section E 503.5.12.2.
E 503.5.12.1 Heating Unenclosed Spaces. Radiant heating shall be used when heating is required for unenclosed spaces.
Exception: Loading docks equipped with air curtains. [ASHRAE 90.1:6.5.8.1]
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APPENDIX E
to permit a determination of compliance by the building official and to indicate compliance with the requirements of this appendix. [ASHRAE 90.1:4.2.2.1] E 503.6.2 Supplemental Information. Supplemental information necessary to verify compliance with this appendix, such as calculations, worksheets, compliance forms, vendor literature, or other data, shall be made available where required by the Authority Having Jurisdiction. [ASHRAE 90.1:4.2.2.2]
E 503.6.3 Manuals. Operating and maintenance information shall be provided to the building owner. This information shall include, but not be limited to, the information specified in Section E 503.6.3.1, Section E 503.6.3.2, and Section E 503.6.5.2. [ASHRAE 90.1:4.2.2.3]
E 503.6.3.1 Required Information. Construction documents shall require that an operating manual and maintenance manual be provided to the building owner. The manuals shall include, at a minimum, the following:
(1) Submittal data stating equipment rating and selected options for each piece of equipment requiring maintenance.
(2) Operation manuals and maintenance manuals for each piece of equipment requiring maintenance. Required routine maintenance actions shall be clearly identified.
(3) Names and addresses of not less than one qualified service agency.
§ 1.8 High relevance — show source text
For SI units: °C = (°F-32)/1.8
- NR = Not Required
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APPENDIX E
(1) Unit controls shall have the mechanical cooling capacity control interlocked with the air economizer controls such that the outdoor air damper is at the 100 percent open position when mechanical cooling is on, and the outdoor air damper does not begin to close to prevent coil freezing due to minimum compressor run time until the leaving air temperature is less than 45°F (7°C).
(2) DX units with a rated capacity no less than 65 000 Btu/h (19 kW) that control the capacity of the mechanical cooling directly based on occupied space temperature shall have not less than two stages of mechanical cooling capacity.
(3) Other DX units, including those that control space temperature by modulating the airflow to the space, shall comply with the requirements of Table E 503.5.3. [ASHRAE 90.1:6.5.1.3]
been previously cooled, either by mechanical cooling or by economizer systems.
(4) Other simultaneous operation of heating and cooling systems to the same zone.
Exceptions:
(1) Zones for which the volume of air that is reheated, recooled, or mixed is less than the larger of the following:
(a) For systems without DDC, 30 percent of the zone design peak supply.
(b) For systems with DDC, the minimum primary airflow rate required to meet the Simplified Procedure ventilation requirements of Chapter 4 or ASHRAE 62.1 for the zone, permitted to be the average airflow rate as allowed by Chapter 4 or ASHRAE 62.1.
(c) Any higher rate that can be demonstrated, to the satisfaction of the Authority Having Jurisdiction, to reduce overall system annual energy use by offsetting reheat/recool energy losses through a reduction in outdoor air intake for the system.
(d) The airflow rate required to be in accordance with applicable codes or accreditation standards, such as pressure relationships or minimum air change rates.
(2) Zones with DDC that comply with the following:
(a) The airflow rate in dead band between heating and cooling does not exceed the larger of the following:
(i) The minimum primary airflow rate required to meet the Simplified Procedure ventilation requirements of Chapter 4 or ASHRAE 62.1 for the zone, permitted to be the average airflow rate as allowed by Chapter 4 or ASHRAE 62.1.
(ii) A higher rate that can be demonstrated, to the satisfaction of the Authority Having Jurisdiction, to reduce overall system annual energy use by offsetting reheat/recool energy losses through a reduction in outdoor air intake.
(iii) The airflow rate required with applicable codes or accreditation standards, such as pressure relationships or minimum air change rates.
(b) The airflow rate that is reheated, recooled, or mixed shall be less than 50 percent of the zone design peak supply rate.
(c) The first stage of heating consists of modulating the zone supply air temperature set
TABLE E 503.5.3
DX COOLING STAGE REQUIREMENTS FOR
MODULATING AIRFLOW UNITS
[ASHRAE 90.1: TABLE 6.5.1.3]
§ 90.1 High relevance — show source text
(2) Demand ventilation systems on 75 percent or more of the exhaust air. Such systems shall be capable of and configured to provide 50 percent or more reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent, and combustion products during cooking and idle.
(3) Listed energy recovery devices that result in a sensible energy recovery ratio of 40 percent or more on 50 percent or more of the total exhaust airflow. A 40 percent sensible energy recovery ratio shall mean a change in the dry-bulb temperature of the outdoor air supply equal to 40 percent of the difference between the outdoor air and entering exhaust air dry-bulb temperatures at design conditions. [ASHRAE 90.1:6.5.7.2.3]
E 503.5.11.2.3 Performance Testing. An approved field test method shall be used to evaluate design air flow rates and demonstrate proper capture and containment performance of installed commercial kitchen exhaust systems. Where demand ventilation systems are utilized
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APPENDIX E
«
E 503.5.12.2 Heating Enclosed Spaces. Radiant heating systems that are used as primary or supplemental heating for enclosed spaces shall be in conformance with the governing provisions of the standard, including, but not limited to the following:
(1) Radiant hydronic ceiling or floor panels (used for heating or cooling).
(2) Combination or hybrid systems incorporating radiant heating (or cooling) panels.
(3) Radiant heating (or cooling) panels used in conjunction with other systems such as VAV or thermal storage systems. [ASHRAE 90.1:6.5.8.2] E 503.5.13 Hot Gas Bypass Limitation. Cooling systems shall not use hot gas bypass or other evaporator pressure control systems unless the system is designed with multiple steps of unloading or continuous capacity modulation. The capacity of the hot gas bypass shall be limited as indicated in Table E 503.5.13 for VAV units and single-zone VAV units. Hot-gas bypass shall not be used on constant-volume units. [ASHRAE 90.1:6.5.9]
TABLE E 503.5.13
HOT GAS BYPASS LIMITATION
[ASHRAE 90.1: TABLE 6.5.9]
RATED CAPACITY MAXIMUM HOT GAS BYPASS
(percent of total capacity)
≤240 000 Btu/h15%
>240 000 Btu/h10% For SI units: 1000 British thermal units per hour = 0.293 kW
E 503.5.14 Door Switches. Conditioned spaces with doors, including doors with more than one-half glass, opening to the outdoors shall be provided with controls that when any such door is open, the following shall occur:
(1) Disable mechanical heating or reset the heating setpoint to 55°F (13°C) or lower within five minutes of the door opening.
§ 62.1 High relevance — show source text
(c) Any higher rate that can be demonstrated, to the satisfaction of the Authority Having Jurisdiction, to reduce overall system annual energy use by offsetting reheat/recool energy losses through a reduction in outdoor air intake for the system.
(d) The airflow rate required to be in accordance with applicable codes or accreditation standards, such as pressure relationships or minimum air change rates.
(2) Zones with DDC that comply with the following:
(a) The airflow rate in dead band between heating and cooling does not exceed the larger of the following:
(i) The minimum primary airflow rate required to meet the Simplified Procedure ventilation requirements of Chapter 4 or ASHRAE 62.1 for the zone, permitted to be the average airflow rate as allowed by Chapter 4 or ASHRAE 62.1.
(ii) A higher rate that can be demonstrated, to the satisfaction of the Authority Having Jurisdiction, to reduce overall system annual energy use by offsetting reheat/recool energy losses through a reduction in outdoor air intake.
(iii) The airflow rate required with applicable codes or accreditation standards, such as pressure relationships or minimum air change rates.
(b) The airflow rate that is reheated, recooled, or mixed shall be less than 50 percent of the zone design peak supply rate.
(c) The first stage of heating consists of modulating the zone supply air temperature set
TABLE E 503.5.3
DX COOLING STAGE REQUIREMENTS FOR
MODULATING AIRFLOW UNITS
[ASHRAE 90.1: TABLE 6.5.1.3]
RATING CAPACITY,
Btu/hMINIMUM NUMBER
OF MECHANICAL
COOLING STAGESMINIMUM
COMPRESSOR
DISPLACEMENT*
≥65 000 and <240 0003 ≤35% of full load
≥240 0004 ≤25% full load For SI units: 1000 British thermal units = 0.293 kW
- For mechanical cooling stage control that does not use variable compressor displacement the percent displacement shall be equivalent to the mechanical cooling capacity reduction evaluated at the full load rating conditions for the compressor.
E 503.5.4 Economizer Heating System Impact. HVAC system design and economizer controls shall be such that economizer operation does not increase the building heating energy use during normal operation.
Exception: Economizers on variable air valve (VAV) systems that cause zone level heating to increase due to a reduction in supply air temperature. [ASHRAE 90.1:6.5.1.4] E 503.5.4.1 Economizer Humidification Sys- tem Impact. Systems with hydronic cooling and humidification systems designed to maintain inside humidity at a dew-point temperature more than 35°F (2°C) shall use a fluid economizer where an economizer is required in accordance with Section E 503.5 through Section E 503.5.4.1. [ASHRAE 90.1:6.5.1.5] E 503.5.5 Simultaneous Heating and Cooling Limitation, Zone Controls. Zone thermostatic controls shall prevent the following:
(1) Reheating.
(2) Recooling.
(3) Mixing or simultaneously supplying air that has been previously mechanically heated and air that has
§ 90.1 High relevance — show source text
(2) Disable mechanical cooling or reset the cooling setpoint to 90°F (32°C) or more within five minutes of the door opening. Mechanical cooling shall be permitted to remain enabled where outdoor air temperature is less than the space temperature.
Exceptions:
(1) Building entries with automatic closing devices.
(2) Any space without a thermostat.
(3) Alterations to existing buildings.
(4) Loading docks. [ASHRAE 90.1:6.5.10]
E 503.6 Submittals. The Authority Having Jurisdiction shall require submittal of compliance documentation and supplemental information in accordance with Section E 503.6.1 through Section E 503.6.3.
E 503.6.1 Construction Details. Compliance documents shall show all the pertinent data and features of the building, equipment, and systems in sufficient detail
TABLE E 503.5.13
HOT GAS BYPASS LIMITATION
[ASHRAE 90.1: TABLE 6.5.9]
For SI units: 1000 British thermal units per hour = 0.293 kW
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to be in accordance with Section E 503.5.11.2.2, additional performance testing shall be required to demonstrate proper capture and containment at minimum airflow. [ASHRAE 90.1:6.5.7.2.4]
E 503.5.11.3 Laboratory Exhaust Systems. Buildings with laboratory exhaust systems having a total exhaust rate of more than 5000 ft [3] /min (2.3597 m [3] /s) shall include not less than one of the following features:
(1) VAV laboratory exhaust and room supply systems capable of and configured to reduce exhaust and makeup airflow rates, incorporate a heat recovery system to precondition makeup air from laboratory exhaust, or both, and shall be in accordance with the following:
A + B - ( E/M ) ≥ 50% (Equation E 503.5.11.3)
Where:
A = Percentage that the exhaust and makeup airflow rates are capable of being reduced from design conditions.
B = Sensible energy recovery ratio.
E = Exhaust airflow rate through the heat recovery device at design conditions.
M = Makeup airflow rate of the system at design conditions.
(2) VAV laboratory exhaust and room supply systems that are required to have minimum circulation rates to be in accordance with the codes or
accreditation standards shall be capable of and configured to reduce zone exhaust and makeup airflow rates to the regulated minimum circulation values, or the minimum required to maintain pressurization relationship requirements. Systems serving nonregulated zones shall be capable of and configured to reduce exhaust and makeup airflow rates to 50 percent of the zone design values, or the minimum required to maintain pressurization relationship requirements.
(3) Direct makeup (auxiliary) air supply of 75 percent or more of the exhaust airflow rate, heated not more than 2°F (1°C) below room setpoint, cooled to not less than 3°F (2°C) above room setpoint, no humidification added, and no simultaneous heating and cooling are used for dehumidification control. [ASHRAE 90.1:6.5.7.3]
E 503.5.12 Radiant Heating Systems. Radiant heating systems shall be in accordance with Section E 503.5.12.1 through Section E 503.5.12.2.
§ 805.5.2 Medium 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:
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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.
§ 140.9 Medium relevance — show source text
- Kitchen ventilation.
A. Mechanically cooled or heated makeup air delivered to any space with a kitchen hood shall not exceed the greater of: i. The supply flow required to meet the space heating and cooling load; or ii. The hood exhaust flow minus the available transfer air from adjacent spaces. Available transfer air is that portion of outdoor ventilation air serving adjacent spaces not required to satisfy other exhaust needs, such as restrooms, not required to maintain pressurization of adjacent spaces, and that would otherwise be relieved from the building. Exception to Section 140.9(b)2A: Existing kitchen makeup air units not being replaced as part of an addition or alteration.
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B. A kitchen/dining facility having a total Type I and Type II kitchen hood exhaust airflow rate greater than 5,000 cfm shall have one of the following: i. At least 50 percent of all replacement air is transfer air that would otherwise be exhausted; or ii. Demand ventilation system(s) on at least 75 percent of the exhaust air. Such systems shall: a. Include controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent and combustion products during cooking and idle; and b. Include failsafe controls that result in full flow upon cooking sensor failure; and c. Include an adjustable timed override to allow occupants the ability to temporarily override the system to full flow; and d. Be capable of reducing exhaust and replacement air system airflow rates to the larger of: (i) 50 percent of the total design exhaust and replacement air system airflow rates; or (ii) The ventilation rate required as specified by Section 120.1(c)3. iii. Listed energy recovery devices with a sensible heat recovery effectiveness of not less than 40 percent on at least 50 percent of the total exhaust airflow; or iv. A minimum of 75 percent of makeup air volume that is:
a. Unheated or heated to no more than 60°F; and
b. Uncooled or cooled without the use of mechanical cooling.
Exception to Section 140.9(b)2B: Existing hoods not being replaced as part of an addition or alteration. 3. Kitchen exhaust system acceptance. Before an occupancy permit is granted for a commercial kitchen subject to Section 140.9(b), 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 specified in NA7.11.
Exception to Section 140.9(b): Healthcare facilities.
(c) Prescriptive requirements for laboratory and factory exhaust systems.
- Airflow reduction requirements. Building laboratory exhaust systems shall be able to reduce zone exhaust and makeup airflow rates to the occupied and unoccupied minimum exhaust airflow rates based on demand and sensed occupancy as follows:
A. Occupied minimum exhaust airflow. When occupant sensing controls sense occupants in the space, the minimum exhaust and makeup airflow rates shall be the greater of: i. User-defined airflow not to exceed 1.0 cfm/ft [2] (equivalent to 6 air changes per hour for a 10-foot high ceiling); or ii.
§ 160.2 Medium relevance — show source text
- 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]
- 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. 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.
§ 160.2 Medium 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.
§ 503.5.6.5 Medium relevance — show source text
covered by Section E 503.5.6.5 and having a fan nameplate electrical input power of less than 180 W or having a motor nameplate horsepower less than
1 / 12 hp (62.1 W) shall meet the fan efficacy requirements specified in ASHRAE 90.1. [ASHRAE 90.1:6.5.3.7]
E 503.5.6.7 Ventilation Design. The required minimum outdoor air rate is the larger of the minimum outdoor air rate or the minimum exhaust air rate
required by Chapter 4, ASHRAE 62.1, ASHRAE 62.2, ASHRAE/ASHE 170, or applicable codes or accreditation standards. Outdoor air ventilation systems shall comply with one of the following:
(1) Design minimum system outdoor air provided shall not exceed 135 percent of the required minimum outdoor air rate.
(2) Dampers, ductwork, and controls shall be provided that allow the system to supply no more than the required minimum outdoor air rate with a single setpoint adjustment.
(3) The system includes exhaust air energy recovery complying with Section E 503.5.10.1.
[ASHRAE 90.1:6.5.3.8]
E 503.5.6.8 Occupied-Standby Controls. Zones serving only rooms that are required to have automatic partial OFF or automatic full OFF lighting controls in accordance with ASHRAE 90.1, where the Chapter 4 or ASHRAE 62.1 occupancy category permits ventilation air to be reduced to zero when
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APPENDIX E
TABLE E 503.5.6.5(1) MINIMUM AVERAGE FULL-LOAD EFFICIENCY FOR POLYPHASE SMALL ELECTRIC MOTORS* [ASHRAE 90.1: TABLE 10.8-3] Col2 Col3 Col4 FULL-LOAD EFFICIENCY, % FULL-LOAD EFFICIENCY, % FULL-LOAD EFFICIENCY, % FULL-LOAD EFFICIENCY, % NUMBER OF POLES OPEN MOTORS OPEN MOTORS OPEN MOTORS NUMBER OF POLES 2 4 6 SYNCHRONOUS SPEED (rpm) 3600 1800 1200 MOTOR SIZE (hp) EFFICIENCY, % EFFICIENCY, % EFFICIENCY, % 0.25 65.6 69.5 67.5 0.33 69.5 73.4 71.4 0.50 73.4 78.2 75.3 0.75 76.8 81.1 81.7 1 77.0 83.5 82.5 1.5 84.0 86.5 83.8 2 85.5 86.5 N/A 3 85.5 86.9 N/A For SI units: 1 horsepower = 0.746 kW
§ 503.5.10.1. Medium relevance — show source text
(3) Systems in Climate Zones 0A, 1A, 2A, and 3A with at least 80 percent outdoor air and employing exhaust air energy recovery complying with Section E 503.5.10.1.
(4) Systems that prevent reheating, recooling, or mixing of heated and cooled supply air.
(5) Systems in which at least 75 percent of the energy for reheating (on an annual basis) is from site recovered energy or on-site renewable energy. [ASHRAE 90.1:6.5.3.5]
E 503.5.6.5 Fractional Horsepower Fan Motors. Motors for fans that are [1] ⁄ 12 hp (62.1 W) or more and less than 1 hp (0.7 kW) shall be electronically-commutated motors or shall have a motor efficiency of not less than 70 percent where rated in accordance with DOE 10 CFR 431. These motors
shall also have the means to adjust motor speed for either balancing or remote control. Belt-driven fans shall be permitted to use sheave adjustments for airflow balancing in lieu of a varying motor speed.
Exceptions:
(1) Motors in the airstream within fan coils and terminal units that operate when providing heating to the space served.
(2) Motors installed in space conditioning equipment certified in accordance with Section E
503.4 through Section E 503.4.4.1.
(3) Motors shown in Table E 503.5.6.5(1) or Table E 503.5.6.5(2). [ASHRAE 90.1:6.5.3.6]
E 503.5.6.6 Low Power Fans. Fans that are not
covered by Section E 503.5.6.5 and having a fan nameplate electrical input power of less than 180 W or having a motor nameplate horsepower less than
1 / 12 hp (62.1 W) shall meet the fan efficacy requirements specified in ASHRAE 90.1. [ASHRAE 90.1:6.5.3.7]
E 503.5.6.7 Ventilation Design. The required minimum outdoor air rate is the larger of the minimum outdoor air rate or the minimum exhaust air rate
required by Chapter 4, ASHRAE 62.1, ASHRAE 62.2, ASHRAE/ASHE 170, or applicable codes or accreditation standards. Outdoor air ventilation systems shall comply with one of the following:
(1) Design minimum system outdoor air provided shall not exceed 135 percent of the required minimum outdoor air rate.
(2) Dampers, ductwork, and controls shall be provided that allow the system to supply no more than the required minimum outdoor air rate with a single setpoint adjustment.
(3) The system includes exhaust air energy recovery complying with Section E 503.5.10.1.
[ASHRAE 90.1:6.5.3.8]
E 503.5.6.8 Occupied-Standby Controls. Zones serving only rooms that are required to have automatic partial OFF or automatic full OFF lighting controls in accordance with ASHRAE 90.1, where the Chapter 4 or ASHRAE 62.1 occupancy category permits ventilation air to be reduced to zero when
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§ 46.45 Medium 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]
§ 170.2 Medium relevance — show source text
Exception 3 to Section 170.2(c)4N2: Any configuration where a DOAS unit provides ventilation air to a downstream fan (a terminal box, air handling unit or other space-conditioning equipment) where the total system airflow can be reduced to ventilation minimum or the downstream fan power is no greater than 0.12 watts per cfm when space temperatures are within the thermostat deadband (at low speed per manufacturer’s literature). 3. DOAS supply and exhaust fans shall have a minimum of three speeds to facilitate system balancing. 4. DOAS with mechanical cooling providing ventilation to multiple zones and operating in conjunction with zone heating and cooling systems shall not use heating or heat recovery to warm supply air above 60°F when representative building loads or outdoor air temperature indicates that the majority of zones requires cooling.
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O. Exhaust air heat recovery. Fan systems designed to operate to the criteria listed in either Table 170.2-I or Table 170.2-J shall include an exhaust air heat recovery system that meets the following: i. A sensible energy recovery ratio of at least 60 percent or an enthalpy recovery ratio of at least 50 percent for both heating and cooling design conditions. ii. Energy recovery bypass or control to disable energy recovery and to directly economize with ventilation air based on outdoor air temperature limits specified in Table 170.2-G. For energy recovery systems where the transfer of energy cannot be stopped, bypass shall prevent the total airflow rate of either outdoor air or exhaust air through the energy recovery exchanger from exceeding 10 percent of the full design airflow rate. iii. For a DOAS unit and a separate independent space-conditioning system meeting the requirements of Section 170.2(c)4Nia, the design supply fan airflow rate shall be the total airflow of only the DOAS unit. Exception to Section 170.2(c)4Oii : DOAS units with the capability to shut off when a separate independent space-conditioning system meets the economizer requirements specified by Section 170.2(c)4Cia is economizing. Exception 1 to Section 170.2(c)4O : Systems meeting Section 140.9(c) prescriptive requirements for laboratory and factory exhaust systems. Exception 2 to Section 170.2(c)4O : Systems serving spaces that are not cooled and that are heated to less than 60°F.
Exception 3 to Section 170.2(c)4O : Where more than 60 percent of the outdoor air heating energy is provided from site-recovered energy in Climate Zone 16. Exception 4 to Section 170.2(c)4O : Sensible recovery ratio requirements at heating design conditions are not required for Climate Zone 15. Exception 5 to Section 170.2(c)4O : Sensible recovery ratio requirements at cooling design conditions are not required for Climate Zone 1. Exception 6 to Section 170.2(c)4O : Where the sum of the airflow rates exhausted and relieved within 20 feet of each other is less than 75 percent of the design outdoor airflow rate, excluding exhaust air that is either: i. Used for another energy recovery system; ii. Not allowed by the California Mechanical Code (Title 24, Part 4) for use in energy recovery systems with leakage potential; or iii.
§ 0.00047 Medium relevance — show source text
ZONE**|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE|PERCENT OUTDOOR AIR AT FULL DESIGN AIRFLOW RATE| |CLIMATE ZONE|≥10% and
<20%|≥20% and
<30%|≥30% and
<40%|≥40% and
<50%|≥50% and
<60%|≥60% and
<70%|≥70% and
<80%|≥80%| |CLIMATE ZONE|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)|DESIGN SUPPLY FAN AIRFLOW RATE (cubic feet per minute)| |3C|NR|NR|NR|NR|NR|NR|NR|NR| |0B, 1B, 2B,
3B, 4C, 5C|NR|≥19 500|≥9000|≥5000|≥4000|≥3000|≥1500|≥120| |0A, 1A, 2A,
3A, 4B, 5B|≥2500|≥2000|≥1000|≥500|≥140|≥120|≥100|≥80| |4A, 5A, 6A,
6B, 7, 8|≥200|≥130|≥100|≥80|≥70|≥60|≥50|≥40|For SI units: 1 cubic foot per minute = 0.00047 m [3] /s
- NR = Not Required
(3) Heating energy recovery where more than 60 percent of the outdoor air heating energy is provided from site-recovered energy or on-site renewable energy.
(4) Enthalpy recovery ratio requirements at heating design condition in Climate Zones 0, 1, and 2.
(5) Cooling energy recovery in climate zones 3C, 4C, 5B, 5C, 6B, 7, and 8.
(6) Where the sum of the airflow rates exhausted and relieved within 20 feet (6096 mm) of each other is less than 75 percent of the design outdoor airflow rate, excluding exhaust air that is;
(a) used for another energy recovery system,
Frequently asked questions
How do I demonstrate compliance at acceptance?
Measure outdoor‑air flow at the system level (and at typical reduced supply conditions for VAV). The code requires documented tests showing measured outside air is within ±10% of the design minimum; acceptance testing and procedures are described in the referenced acceptance/test provisions in the code. § 120.1(f)3 / § 160.2(c)7.C.
Is a fixed damper stop allowed to protect minimum outside air?
No. The code explicitly states that a fixed minimum damper position is not considered dynamic and is not an allowed control strategy for VAV systems; active modulation is required. § 120.1(f)2.
When is demand control ventilation (DCV) required?
DCV is required for qualifying spaces (high occupant density, systems with economizers, modulating OA control, or design OA > 3,000 cfm) per the DCV criteria; in multifamily and nonresidential chapters the DCV and sensor rules are spelled out in § 120.1(d)4 and § 160.2(c)5D.
What if a CO2 sensor fails during operation?
Controls must provide a signal that resets to supply the minimum quantity of outside air required by the design (i.e., revert to design minimum OSA) whenever the CO2 sensor is failed. § 120.1(d)4F / § 160.2(c)5D(vi).
For multifamily whole‑dwelling ventilation, how is the total required ventilation calculated?
Use Equation 160.2‑B: Qtot = 0.03 × Afloor + 7.5 × (Nbr + 1) (cfm). See § 160.2(b)(iv) and associated multifamily requirements for system types and controls.
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