For LEED calculations, the baseline case is defined as the building with fixtures that meet the Energy Policy Act requirements (see page 100 of the LEED v2.1 Reference Guide for EPACT fixture ratings), NOT the actual fixtures existing prior to retrofit. The design case is defined as the building with the actual fixtures installed. In the project cited, this would include the new fixtures installed AND the existing fixtures remaining.The calculation methodology for this credit is described in detail in the LEED Reference Guide. The LEED v2.0 Calculator and the v2.1 Letter Template provides spreadsheets for creating the baseline and the design cases. The calculations are based on the building occupants\' usage of fixture types. For both the baseline and design cases, the occupants\' usage patterns need to be consistent, which includes the number of occupants, frequency and duration of use for male and female of a fixture type with the corresponding water volume consumed (in gallons per minute or gallons per flush).The proposed methodology for occupant use of the new fixtures (80%) and the existing fixtures (20%) is acceptable, but only if entire restrooms have been retrofitted with new fixtures. If there has been a mix of new and existing fixtures within one or more restrooms, a different methodology must be developed by the project team and justified based on the use patterns of the individual restrooms. Applicable Internationally.