Space types such as ventilated parking garage, attics, and crawlspaces are defined by Standard 90.1-2019 as unenclosed spaces, and for the purposes of envelope requirements, envelope components adjacent to them are treated as exterior surfaces. Therefore, the following rules apply:
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Baseline |
Proposed |
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Envelope |
Demising Walls: The baseline envelope for spaces (conditioned, semi-heated, and plenum) adjacent to unenclosed spaces shall be considered exterior and modeled with the baseline exterior envelope requirements. |
As designed |
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Exterior Walls: Surfaces separating unenclosed spaces from the exterior shall be modeled to be the same as the proposed building. |
As designed |
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All Other Surfaces: All other surfaces, except those classified as ‘Semi-Exterior’ or ‘Exterior’ shall be modeled to be the same as proposed. |
As designed |
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Window-to-Wall Ratio (WWR) Calculation: As designed |
As designed |
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Skylight Roof Ratio (SRR) Calculation: Only exterior roofs for enclosed spaces are included in the calculation of skylight area, hence exterior roof area for parking garages, attics or crawlspaces shall not be considered in the calculation of the skylight area. |
As designed |
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Lighting |
The lighting power allowance for attics and crawlspaces shall be 0 W/ft2 for the baseline building unless the space is used as a storage or mechanical room, in which case the lighting power density (LPD) would be the value defined in Table G3.7 of Standard 90.1-2019. For attics, LPDs should be used in conjunction with floor area that has headroom height of 7.5 ft or greater. The lighting power allowance for parking garages is defined in Table G3.8 of Standard 90.1-2019. |
As designed |
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HVAC System |
Ventilated parking garages, attics, and crawlspaces shall be excluded from the floor area used to determine the baseline HVAC system. |
As designed |
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If these unenclosed spaces have space conditioning or a mechanical ventilation system, the systems are assumed to be the same in both proposed and baseline models. |