CALGreen Section: 5.506.2 Carbon dioxide (CO2) monitoring. For buildings equipped with demand control ventilation, CO2 sensors and ventilation controls shall be specified and installed in accordance with the requirements of 2010 California Energy Code, Section 121(c).
Intent:
When demand control ventilation is required by Part 6, this provision intends to maintain CO2
levels which are within the range that is safe for human occupation.
Existing Law or Regulation:
The current edition of the California Energy Code, CCR, Title 24, Part 6, Section 121(c) identifies the sensors, controls and devices required to keep CO2 emissions at safe levels.
Compliance Method:
Design Team: The designer should specify and show calculations and locations for CO2 sensors in the construction documents. The team familiar with demand control ventilation will be familiar with these requirements.
Contractor: The contractor should install the specified equipment and make sure that it is operating as designed. Again, familiarity with demand control ventilation will be an advantage.
Suggestion:
Contractor: Retain product data sheets for onsite verification by the enforcing agency and for the operation and maintenance manual.
Enforcement:
Plan Intake: The reviewer and/or plan checker should review the plans, specifications and calculations to confirm that sensors are included which meet the requirements of Part 6.
On-Site Enforcement: The inspector should review the permit set of plans and product data sheets to verify that complying sensors displaying readings are installed in designated locations. He/she should obtain assurance that the readings are recorded as required by Part 6.
CALGreen Section: 5.714.7.3 Carbon dioxide (CO2) monitoring. [BSC] For buildings equipped with demand control ventilation, CO2 sensors and ventilation controls shall be specified and installed in accordance with the requirements of 2010 California Energy Code, Section 121(c).
Intent:
This section intends to provide clarity to the code user regarding carbon dioxide monitoring systems to protect occupant health and minimize GHG emissions. It is limited to additions and
alterations to buildings equipped with demand control ventilation and as provided in theCalifornia
Energy Code, Part 6, Title 24.
Compliance and Enforcement: See § 5.506.2 of this guide
NONRESIDENTIAL, HIGH-RISE RESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—MANDATORY REQUIREMENTS
NONRESIDENTIAL, HIGH-RISE RESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—MANDATORY REQUIREMENTS
be reduced below the level required by Section
121(b)2 for up to 5 minutes each hour if the average rate for each hour is equal to or greater than the required ventilation rate.
B. CO2 sensors shall be located in the room between 3 ft and 6 ft above the floor or at the anticipated height of the occupants heads;
C. Demand ventilation controls shall maintain CO
Note: VAV must comply with Section 121(c)1 at min- imum supply airflow.
2. Pre-occupancy. The lesser of the minimum rate of out- door air required by Section 121(b)2 or three complete air changes shall be supplied to the entire building dur- ing the one-hour period immediately before the build- ing is normally occupied.
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concentrations less than or equal to 600 ppm plus the
outdoor air CO2 concentration in all rooms with CO2
sensors;
Exception to Section 121(c)4C: The outdoor air ventilation rate is not required to be larger than the design outdoor air ventilation rate required by Sec- tion 121(b)2 regardless of CO2 concentration.
3. Required demand control ventilation. HVAC sys-
D. Outdoor air CO2
concentration shall be determined
tems with the following characteristics shall have
demand ventilation controls complying with Section
121(c)4:
A. They have an air economizer; and
by one of the following:
i. CO2 concentration shall be assumed to be 400 ppm without any direct measurement; or
ii. CO2 concentration shall be dynamically mea-
B. They serve a space with a design occupant density,
sured using a CO2
sensor located within 4 ft of
or a maximum occupant load factor for egress pur-
poses in the CBC, greater than or equal to 25 people per 1000 ft2 (40 square feet per person); and
C. They are either:
i. Single zone systems with any controls; or
ii. Multiple zone systems with Direct Digital Con- trols (DDC) to the zone level.
Exception 1 to Section 121(c)3: Classrooms, call centers, office spaces served by multiple zone sys-
the outdoor air intake.
E. When the system is operating during hours of expected occupancy, the controls shall maintain sys- tem outdoor air ventilation rates no less than the rate listed in Table 121-A times the conditioned floor area for spaces with CO2 sensors, plus the rate required by Section 121(b)2 for other spaces served by the system, or the exhaust air rate, whichever is greater.
F. CO sensors shall be certified by the manufacturer to
tems that are continuously occupied during normal
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be accurate
within plus or minus 75 ppm at a 600 and
business hours with occupant density greater than
25 people per 1000 ft2 per Section 121(b)2B, healthcare facilities and medical buildings, and public areas of social services buildings are not required to have demand control ventilation.
Exception 2 to Section 121(c)3: Where space exhaust is greater than the design ventilation rate specified in Section 121(b)2B minus 0.2 cfm per ft2 of conditioned area.
Exception 3 to Section 121(c)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, or beauty salons shall not install demand control ventilation.
Exception 4 to Section 121(c)3: Spaces with an area of less than 150 square feet, or a design occu- pancy of less than 10 people per Section 121(b)2B.
4. Demand control ventilation devices.
A. For each system with demand control ventilation, CO2 sensors shall be installed in each room that meets the criteria of Section 121(c)3B with no less than one sensor per 10,000 ft2 of floor space. When a zone or a space is served by more than one sensor, a signal from any sensor indicating that CO2 is near or at the setpoint within a space shall trigger an increase in ventilation to the space;
1000 ppm concentration when measured at sea level and 25°C, factory calibrated or calibrated at start-up, and certified by the manufacturer to require calibra- tion 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
121(b)(2) to the zone serviced by the sensor at all times that the zone is occupied.
G. The CO2 sensor(s) reading for each zone shall be dis- played continuously, and shall be recorded on sys- tems with DDC to the zone level.
(d) Ducting for zonal heating and cooling units. Where a return plenum is used to distribute outdoor air to a zonal heat- ing or cooling unit, which then supplies the air to a space in order to meet the requirements of Section 121(b)2, the outdoor air shall be ducted to discharge either:
1. Within 5 feet of the unit; or
2. Within 15 feet of the unit, substantially toward the unit, and at a velocity not less than 500 feet per minute.
(e) Design and control requirements for quantities of outdoor air. All mechanical ventilation and space-condition- ing systems shall be designed with and have installed ductwork, dampers and controls to allow outside air rates to be operated at the larger of (1) the minimum levels specified in Section 121(b)1; or (2) the rate required for make-up of exhaust systems that are required for a process, for control of odors, or for the removal of contaminants within the space.
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