ASHRAE-90.1-2022- - Page 082

Extracted Content

Table 6.4.3.8 Demand Control Ventilation (DCV) Floor Area Thresholds

Climate Zone	Occupant Outdoor Airflow Component (cfm/1000 ft2) a	Col3	Col4	Col5	Col6	Col7
Climate Zone	100 to 199	200 to 399	400	100 to 199	200 to 399	400
Climate Zone	Minimum Space Floor Area in ft2 where DCV Is Required	Minimum Space Floor Area in ft2 where DCV Is Required	Minimum Space Floor Area in ft2 where DCV Is Required	Minimum Space Floor Area in ft2 where DCV Is Required	Minimum Space Floor Area in ft2 where DCV Is Required	Minimum Space Floor Area in ft2 where DCV Is Required
Climate Zone	Areas without Exhaust Air Energy Recovery	Areas without Exhaust Air Energy Recovery	Areas without Exhaust Air Energy Recovery	Areas with Exhaust Air Energy Recovery b	Areas with Exhaust Air Energy Recovery b	Areas with Exhaust Air Energy Recovery b
7, 8	400	200	150	800	400	250
5A, 6A, 6B	600	250	150	1400	900	400
0A, 0B, 1B, 3A, 4A, 5B, 5C	800	400	250	2000	1000	500
2A, 2B, 4C	1100	600	300	2300	1100	600
3B, 4B	1500	700	400	5200	2350	1250
1A	2400	1100	600	5800	2600	1400
3C	7000	3000	1700	12,000	6000	3000

a. Occupant outdoor airflow component in cfm per 1000 ft [2] shall be calculated as the product of default occupant density and outdoor airflow rate per occu pant ( Rp ) as shown in ASHRAE Standard 62.1, Table 6.2.2.1. b. Where exhaust air energy recovery is required by Section 6.5.6.1.

required by accreditation standards, and where humidistatic controls are capable of and configured to maintain a dead band of at least 10% rh where no active humidification or dehumidification takes place.

Exception to 6.4.3.6.1, 6.4.3.6.2, and 6.4.3.6.3: Systems serving zones where humidity levels are

required to be maintained with precision of not more than ±5% rh to comply with applicable codes or accreditation standards or as approved by the authority having jurisdiction .

6.4.3.7 Freeze Protection and Snow/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 above 40°F 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 above 50°F and no precipitation is falling, and an automatic or manual control that will allow shutoff when the outdoor temperature is above 40°F so that the potential for snow or ice accumulation is negligible.

6.4.3.8 Ventilation Controls for High-Occupancy Areas. Demand control ventilation ( DCV ) is required for spaces larger than the floor area shown in Table 6.4.3.8 based on an occupant outdoor airflow component in cfm per 1000 ft [2] and served by systems with one or more of the following:

a. Air economizer b. Automatic modulating control of outdoor air damper c. Design outdoor airflow greater than 3000 cfm

Exceptions to 6.4.3.8:

1. Multiple-zone systems without DDC of individual zones communicating with a central control panel.
2. Spaces where >75% 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 .
3. Spaces with one of the following occupancy categories as defined in ASHRAE Standard 62.1: correctional cells, daycare sickrooms, science labs, barbers, beauty and nail salons, and bowling alley seating.
4. Spaces where the requirements of ASHRAE Standard 170, applicable codes, or applicable accreditation standards do not allow the reduction of outdoor airflow.

Informative Note: ASHRAE Guideline 36 includes detailed sequences of control for CO2-based demand control ventilation and how it can be implemented while complying with ASHRAE Standard 62.1.

80 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)