ASHRAE-90.1-2022- - Page 318

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including those used for infiltration, occupants, lighting, gas and electricity using equipment, shall be equal to the highest hourly value used in the annual simulation runs and applied to the entire design day. For heating sizing runs, schedules for internal loads, including those used for occupants, lighting, gas and electricity using equipment, shall be equal to the lowest hourly value used in the annual simulation runs, and schedules for infiltration shall be equal to the highest hourly value used in the annual simulation runs and applied to the entire design day.

Exception to G3.2.2.2.1: For cooling sizing runs in residential dwelling units, the infiltration, occu pants, lighting, gas and electricity using equipment hourly schedule shall be the same as the most used hourly weekday schedule from the annual simulation.

G3.2.2.3 Unmet Loads. Unmet load hours for the proposed design or baseline building design shall not exceed 300 (of the 8760 hours simulated). Alternatively, unmet load hours exceeding these limits shall be permitted to be accepted upon approval of the rating authority, provided that sufficient justification is given indicating that the accuracy of the simulation is not significantly compromised by these unmet loads.

G3.2.2.4 Ventilation. Minimum ventilation system outdoor air intake flow shall be the same for the proposed design and baseline building design .

Exceptions to G3.2.2.4:

1. When modeling demand control ventilation in the proposed design in systems with outdoor air capacity less than or equal to 3000 cfm serving areas with an average design capacity of 100 people per 1000 ft [2] or less.
2. When designing systems in accordance with Standard 62.1, Section 6.2, “ Ventilation Rate Procedure,” reduced ventilation airflow rates may be calculated for each HVAC zone in the proposed design with a zone air distribution effectiveness ( Ez ) > 1.0 as defined by Standard 62.1, Table 6-2. Baseline ventilation airflow rates in those zones shall be calculated using the proposed design Ventilation Rate Procedure calculation with the following change only. Zone air distribution effectiveness shall be changed to ( Ez ) = 1.0 in each zone having a zone air distribution effectiveness ( Ez ) > 1.0. Proposed design and baseline building design Ventilation Rate Procedure calculations, as described in Standard 62.1, shall be submitted to the rating authority to claim credit for this exception.
3. Where the minimum outdoor air intake flow in the proposed design is provided in excess of the amount required by the building code or the rating authority, the baseline building design shall be modeled to reflect the greater of that required by either the rating authority or the building code and will be less than the proposed design .
4. For baseline systems serving only laboratory spaces that are prohibited from recirculating return air by code or accreditation standards, the baseline system shall be modeled as 100% outdoor air .

G3.2.2.5 Economizers. Air economizers shall not be included in baseline HVAC Systems 1, 2, 9, and 10. Integrated air economizer control shall be included in baseline HVAC Systems 3 through 8, and 11, 12, and 13 based on climate as specified in Table G3.2.2.5. Exceptions to G3.2.2.5: Economizers shall not be included for systems meeting one or more of the

exceptions listed below.

1. Systems that include gas-phase air cleaning to meet the requirements of Standard 62.1, Section 6.1.2. This exception shall be used only if the system in the proposed design does not match the building design.
2. Where the use of outdoor air for cooling will affect supermarket open refrigerated casework sys- tems . This exception shall only be used if the system in the proposed design does not use an economizer. If the exception is used, an economizer shall not be included in the baseline building design .
3. Systems that serve computer rooms complying with Section G3.2.2.5.1.

G3.2.2.5.1 Computer Room Economizers. Systems that serve computer rooms that are HVAC System 3 or 4 shall not have an economizer. Systems that serve computer rooms that are HVAC System 11 shall include an integrated fluid economizer meeting the requirements of Section 6.5.1.2 in the baseline building design .

G3.2.2.6 Economizer High-Limit Shutoff. The high-limit shutoff shall be a dry-bulb fixed switch with set-point temperatures in accordance with the values in Table G3.2.2.6.

G3.2.2.7 Design Airflow Rates

G3.2.2.7.1 Baseline All System Types Except System Types 9 and 10. System design supply airflow rates for the baseline building design shall be based on a supply-air-to-room temperature set-point difference of 20°F or the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or

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