Requirements
Have permanently installed water meters that measure the total potable water use for the project and associated grounds. All potable or reclaimed water supplied to the project must be metered.
For Interiors projects, have permanently installed sub-meters that measure total potable water use for any fixtures or fittings in the project scope. Alternately, interiors projects may pro-rate water use, using occupancy and base building water use over twelve consecutive months.
Measure total potable water use on a monthly basis for twelve consecutive months (one full year).
Input the twelve months of potable water use data into the Arc Platform, and calculate a Water Performance Score for the project.
For initial certification, obtain a minimum Water Performance Score of 40. Additional points for this prerequisite are awarded for Water Performance Scores above 40, according to Table 1.
Interiors projects that do not have fixtures or fixture fittings in the project scope are exempt from the requirement to obtain a minimum Water Performance Score of 40 but must provide twelve months of base building potable water use data, pro-rated by occupancy, and calculate a Water Performance Score for the project.
Table 1. LEED Points for Water Performance
|
Water Performance Score
|
LEED Points
|
|
40 (Required for initial certification)
|
6 (Required for initial certification)
|
|
44
|
7
|
|
50
|
8
|
|
57
|
9
|
|
64
|
10
|
|
70
|
11
|
|
77
|
12
|
|
84
|
13
|
|
90
|
14
|
|
97
|
15
|
Water Performance Score
The water performance score rates the building’s total water consumption against the total water consumption of comparable high-performing LEED certified buildings.
The score is a value from 1-100 based on the project’s water consumption per occupant and water consumption per floor area.
Performance Score calculation
To calculate a water performance score, the following data is required:
- Annual water consumption (gallons), with monthly or daily totals
- Gross floor area (sq. ft. or sq. m.)
- Weighted occupancy
- Weighted operating hours
The water consumption is adjusted for weighted operating hours and converted into daily water consumption using Equation 1.
Equation 1: adjusted daily water consumption * operating hours adjustment factor / 365 days
The operating hours adjustment factor is determined using Table 2. The adjustment factor accounts for typical LEED buildings operations of 50 hours a week.
Table 2. Operating hours adjustment factor
Daily water consumption per occupant is calculated by dividing the daily water consumption by the weighted occupancy, using Equation 2.
Equation 2: adjusted daily water consumption per occupant = daily water consumption / weighted occupancy
Daily water consumption per floor area is calculated by dividing the daily water consumption by the
gross floor area, using Equation 3.
Equation 3: adjusted daily water consumption per floor area = daily water consumption /
gross floor area
The project’s daily water consumption per occupant AND daily water consumption per floor area are input into the water scoring function for the specific project type to produce a water performance score.
The water scoring functions were developed using water consumption data from high-performing buildings. The data set includes LEED buildings that shared their water consumption data with USGBC as part of the
whole-building energy and water usage requirement.
