ASHRAE-90.1-2022- - Page 307

Extracted Content

G3.2 Performance Calculations for New Buildings, Additions and Substantial Alterations

G3.2.1 Baseline HVAC System Type and Description. HVAC systems in the baseline building design shall be selected based on the building area types and criteria described in Section G3.2.1.1 and shall be adjusted, when applicable, based on the requirements in Section G3.2.1.2 and modeled in the baseline build- ing design per Section G3.2.1.3.

G3.2.1.1 Baseline HVAC System Types based on Building Area Types. HVAC system types in the baseline building design shall be determined as follows:

a. Determine the combined area of the gross conditioned floor area and semiheated floor area of each of

the following building area types in the proposed design:

1. Residential. HVAC zones that include dwelling units, guest rooms, living quarters, private living spaces, and sleeping quarters, and residential associated HVAC zones shall be classified as residen- tial . Other space types, including patient rooms in hospitals, shall not be classified as residential.
2. Public Assembly. Houses of worship, auditoriums, movie theaters, performance theaters, concert halls, arenas, enclosed stadiums, ice rinks, gymnasiums, convention centers, exhibition centers, and natatorium buildings shall be classified as public assembly. HVAC zones that include these area types in other buildings shall also be classified as public assembly.
3. Heated-Only Storage. Nonrefrigerated warehouse buildings and heated parking garages that are not mechanically cooled, shall be classified as heated-only storage.
4. Retail. Grocery stores, retail stores, and supermarket buildings with two floors or fewer shall be classified as retail.
5. Hospitals. Hospital building area types, including patient rooms, shall be classified as hospitals.
6. Other Nonresidential. Buildings and areas within buildings that are not classified as residential, public assembly, heated-only storage, hospital, or retail shall be classified as other nonresidential . b. Classify the nonresidential building area type with the largest combined area from Section G3.2.1.1(a) as

the predominant nonresidential building area type. Add the combined area of any remaining nonresiden- tial building area types with less than 20,000 ft [2] to the combined area of the predominant nonresidential building area type. c. Select a baseline HVAC system type from Table G3.1.1-3 for each of the following building area types

included in the proposed design :

1. Residential based on Section G3.2.1.1(a)
2. Predominant nonresidential based on Section G3.2.1.1(b)
3. Each additional nonresidential building area type with more than 20,000 ft [2] of combined area based on Section G3.2.1.1(a)

G3.2.1.2 Additional and Adjusted Baseline HVAC System Types. Baseline HVAC systems shall be added or adjusted for individual HVAC zones based on the following criteria.

a. If the baseline HVAC system type is 5, 6, 7, or 8 use separate single-zone systems conforming with the

requirements of system 3 or system 4 for any HVAC zones that have occupancy, or internal gains that differ significantly from the rest of the HVAC zones served by the system . Total peak internal gains that also differ by 12 Btu/h·ft [2 ] or more from the average of other HVAC zones served by the system, or occupied hours that are more than 40 hours per week higher than the average of other HVAC zones served by the system, are considered to differ significantly. Examples where this exception may be applicable include, but are not limited to, commercial kitchens, auditoriums, natatoriums, and continually occupied security areas. This exception does not apply to computer rooms . b. In a building having a total laboratory exhaust rate greater than 15,000 cfm, use a single system of type 5

or 7 serving only those HVAC zones that include the laboratory spaces . The lab exhaust fan shall be modeled as constant horsepower reflecting constant-volume stack discharge with outdoor air bypass. c. HVAC zones designed with heating-only systems in the proposed design serving storage rooms, stairwells,

vestibules, electrical/mechanical rooms, and restrooms not exhausting or transferring air from mechanically cooled thermal zones in the proposed design shall use system type 9 or 10 in the baseline building design . d. If the baseline HVAC system type is 9 or 10, use additional system types for all HVAC zones that are

mechanically cooled in the proposed design . The baseline HVAC system types for such zones shall be determined based on the building area type determined in accordance with Section G3.2.1.1(a) and the requirements of Section G3.2.1.1(c).

ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 305