ASHRAE-90.1-2022- - Page 163

Extracted Content

a. For each space enclosed by partitions that are 80% of the ceiling height or taller, determine the appropri ate space type and the corresponding LPD allowance from Tables 9.5.2.1-1 and 9.5.2.1-2. If a space has multiple functions, where more than one space type is applicable, that space shall be broken up into smaller subspaces, each using its own space type from Tables 9.5.2.1-1 and 9.5.2.1-2. Any of these subspaces that are smaller in floor area than 20% of the original space and less than 1000 ft [2] need not be broken out. Include the floor area of balconies and other projections in this calculation. b. In calculating the area of each space and subspace, the limits of the area are defined by the centerline of

interior walls, the dividing line between subspaces, and the outside surface of exterior walls or semiexte- rior walls . For the purposes of this section, semiexterior walls that separate semiheated space from con- ditioned space shall be considered interior walls. c. Based on the space type selected for each space or subspace, determine the lighting power allowance of

each space or subspace by multiplying the calculated area of the space or subspace by the appropriate LPD allowance determined in Section 9.5.2.1(a). For space types not listed, selection of a reasonable equivalent category shall be permitted. d. The interior lighting power allowance is the sum of lighting power allowances of all spaces and sub spaces. Trade-offs among spaces and subspaces are permitted, provided that the total installed interior lighting power does not exceed the interior lighting power allowance .

9.5.2.2 Additional Interior Lighting Power. When using the Space-by-Space Method, an increase in the interior lighting power allowance is allowed for specific lighting functions. Additional power shall be allowed only if the specified lighting is installed and controlled independently of the general lighting in accordance with Table 9.5.2.2. This additional power shall be used only for the specified luminaires and shall not be used for any other purpose unless otherwise indicated. Lighting control requirements referenced in Section 9.5.2.2 are the only required controls for these applications.

An increase in the interior lighting power allowance is permitted in the following cases:

a. For each space in which lighting is installed in addition to the general lighting for the purpose of decora tive appearance or for highlighting art or exhibits not exempted in Table 9.2.2.1, provided that the additional lighting power shall not exceed the value in Table 9.5.2.2 . b. For lighting equipment installed in sales areas and specifically designed and directed to highlight mer chandise, provided that the additional lighting power shall not exceed the value in Table 9.5.2.2. c. For spaces in which lighting is installed for the purpose of videoconferencing and the lighting in that

space meets ANSI/IES/AVIXA RP-38, additional lighting power shall be allowed per Table 9.5.2.2.

Exception to 9.5.2.2: Other merchandise categories may be included in Retail Areas 2 through 4 above,

provided that justification documenting the need for additional lighting power based on visual inspection, contrast, or other critical display is approved by the authority having jurisdiction .

9.5.2.3 Additional Interior Lighting Power Using Nonmandatory Controls. An additional lighting power allowance shall be permitted for space types with nonmandatory controls installed as identified in Table 9.5.2.3 when all mandatory controls are used according to Section 9.4. This allowance is added to the interior lighting power allowance and is calculated as follows:

Additional Interior Lighting Power Allowance = Lighting Power Under Control × Control Factor where Lighting Power Under Control = the total input watts of all lamps being controlled using the control method indicated Control Factor = the value given in Table 9.5.2.3 for the corresponding space type and control method 9.5.2.4 Room Geometry Adjustment. When using the Space-by-Space Method, an adjustment of the space LPD allowance is permitted for individual spaces where room cavity ratio ( RCR ) calculated for the empty room is documented to be greater than the RCR threshold for that space type shown in Tables 9.5.2.1-1 and 9.5.2.1-2.

RCR = 2.5 × Room Cavity Height × Room Perimeter Length/Room Area where Room Cavity Height = Luminaire Mounting Height – Workplane.

For corridor/transition spaces, this adjustment is allowed when the corridor is less than 8 ft wide, regardless of the RCR .

The LPD allowance for these spaces may be increased by the following amount:

LPD Increase = Base Space LPD × 0.20 where Base Space LPD = the applicable LPD allowance from Tables 9.5.2.1-1 and 9.5.2.1-2.

ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 161