ASHRAE-90.1-2022- - Page 316
Extracted Content
d. The baseline HVAC system serving HVAC zones that include computer rooms shall be modeled in accor dance with one of the following:
- Baseline System 11 shall be used for such HVAC zones in buildings with a total computer room peak cooling load greater than 3,000,000 Btu/h.
- Baseline S ystem 11 shall be used for such HVAC zones in buildings where the baseline HVAC system type is 7 or 8 and the total computer room peak cooling load is greater than 600,000 Btu/h.
- Baseline System 3 or 4 shall be used for all other HVAC zones that include computer rooms based on climate zone. e. Residential associated HVAC zones shall use system type 3 or 4 based on climate zone.
G3.2.1.3 For baseline HVAC systems 1, 2, 3, 4, 9, 10, 11, 12, and 13, each HVAC zone or thermal block shall be modeled with its own HVAC system . For Systems 5, 6, 7, and 8, each floor shall be modeled with a separate HVAC system . Floors with identical HVAC zones or thermal blocks can be grouped for modeling purposes.
Exception to G3.2.1.3: Baseline system 5 or 7 serving laboratory spaces in accordance with Section
G3.2.1.2(b).
G3.2.1.4 Purchased Heat. For systems using purchased hot water or steam, the heating source shall be modeled as purchased hot water or steam in both the proposed design and baseline building design . Hotwater or steam costs shall be based on actual utility rates, and on- site boilers, electric heat, and furnaces shall not be modeled in the baseline building design .
G3.2.1.5 Purchased Chilled Water. For systems using purchased chilled water, the cooling source shall be modeled as purchased chilled water in both the proposed design and baseline building design . Purchased chilled-water costs shall be based on actual utility rates, and on- site chillers and direct expansion equipment shall not be modeled in the baseline building design .
G3.2.1.6 Baseline HVAC System Requirements for Systems Utilizing Purchased Chilled Water and/or Purchased Heat. If the proposed design uses purchased chilled water and/or purchased heat, the following modifications to the baseline HVAC system types in Table G3.1.1-4 shall be used.
G3.2.1.6.1 Purchased Heat Only. If the proposed design uses purchased heat, but does not use purchased chilled water, then Tables G3.1.1-3 and G3.1.1-4 shall be used to select the baseline HVAC system type, and purchased heat shall be substituted for the heating type in Table G3.1.1-4. The same heating source shall be used in the proposed design and baseline building design .
G3.2.1.6.2 Purchased Chilled Water Only. If the proposed design uses purchased chilled water but does not use purchased heat, then Tables G3.1.1-3 and G3.1.1-4 shall be used to select the baseline HVAC system type, with the modifications listed below:
a. Purchased chilled water shall be substituted for the cooling types in Table G3.1.1-4. b. System 1 and 2 shall be constant-volume fan-coil units with fossil fuel boilers . c. System 3 and 4 shall be constant-volume single-zone air handlers with fossil fuel furnaces. d. System 7 shall be used in place of System 5. e. System 8 shall be used in place of System 6.
G3.2.1.6.3 Purchased Chilled Water and Purchased Heat. If the proposed design uses purchased chilled water and purchased heat, then Tables G3.1.1-3 and G3.1.1-4 shall be used to select the baseline HVAC system type, with the following modifications:
a. Purchased heat and purchased chilled water shall be substituted for the heating types and cooling types in
Table G3.1.1-4. b. System 1 shall be constant-volume fan-coil units. c. System 3 shall be constant-volume single-zone air handlers. d. System 7 shall be used in place of System 5.
G3.2.1.6.4 On-Site Distribution Pumps. All on- site distribution pumps shall be modeled in both the proposed design and base building design .
G3.2.1.7 Modeling Building Envelope Air Leakage. The air leakage rate of the building envelope ( I75Pa ) at a pressure differential of 75 Pa (0.30 in. of water) shall be converted to appropriate units for the simulation program using one of the following formulas:
For methods describing air leakage as a function of floor area,
IFLR = 0.112 × I75Pa × S / AFLR
314 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)