We have a question about the baseline and proposed lighting for tenant spaces, and more specifically how to input those in the LEED v4 Minimum Energy Performance Calculator v05 spreadsheet.
Per the ASHRAE 90.1-2019 User's Manual, section G3.1-6, the LPD for the baseline building must be determined using either the Building Area or Space-by-Space Method. The categorization of spaces must be identical between proposed and baseline buildings. For the proposed building lighting system, if there are any areas of the building for which the lighting systems are not defined, then those areas are modeled using base interior LPDs for both the proposed and baseline runs (based on the Building Area Method). In the special case where no lighting system or design exists, as in a shell building where the lighting will be installed by a future tenant, then a default lighting power must be assumed, based on the Building Area Method for the appropriate space type. If no space type is known, then "office" is assumed.
So, for example in a high-rise core and shell building we would model the tenant office spaces under the Building Area Method, with 0.90 W/sf LPD as per Table 9.5.1. Within the same building, however, there are core spaces with the lighting system designed (lobbies and restrooms, for example). Ideally those would be classified using the Space-by-Space Method. We would therefore have a building which is using both the Building Area Method and the Space-by-Space Method. Section 188.8.131.52 allows this mix if the tenant spaces are separately metered or permitted.
If we want to complete the Minimum Energy Performance Calculator v05, lighting tab, however, we have to choose between the Building Area Method and the Space-by-Space method. The spreadsheet does not appear to accommodate for a mix of the two.
Are we allowed to use a mix of Building Area Method and Space-by-Space method? If so, how is it documented in the Minimum Energy Performance Calculator spreadsheet?