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LEED v4.1

Existing Buildings

Water Efficiency
Water Performance

LEED CREDIT

EBOM-v4.1 WEc1: Water Performance 15 points

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Dan Ackerstein

Ackerstein Sustainability, LLC
Principal

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© Copyright U.S. Green Building Council, Inc. All rights reserved.

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:
  1. Annual water consumption (gallons), with monthly or daily totals
  2. Gross floor area (sq. ft. or sq. m.)
  3. Weighted occupancy
  4. 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. See all forum discussions about this credit »

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Addenda

2/6/2023Updated: 2/9/2023
Rating System Correction
Description of change:
Edit the fifth and sixth paragraphs to read as:
"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. "

Add "for initial certification" to each of the required values in Table 1.
Campus Applicable
No
Internationally Applicable:
No
2/6/2023Updated: 2/9/2023
Reference Guide Correction
Description of change:
Under Step By Step, Step 3:
- revise title of Step 3 to be: "Input Water Data"
- Revise first bullet to be: "Upload Arc Data Template"
- Replace "manually" in bullet 4 with "directly"

Add the following language after the bullet points:
"It is recommended to provide data formatted with each water meter listed separately. If providing combined data include a calculation or summary table showing how the values were determined. Only combine data from meters with identical service dates.

Classify the following water sources as potable water:
- Municipally supplied potable water, well water, groundwater, and naturally occurring surface bodies of water (such as streams, lakes, or rivers)

Classify the following alternative water sources as reclaimed:
Municipally supplied reclaimed wastewater (“purple pipe” water), graywater, rainwater, stormwater, treated seawater, water recovered from condensate, foundation dewatering water, treated blowdown from process water, reverse osmosis reject water, and other recycled water sources."


Add the following language to the paragraph that starts "You do not have to enter....":
"If a water meter is not used for part of the year (e.g. months outside of the irrigation season, or the meter went out of service/was replaced) make sure the data for the meter includes the entire year by including zero for the months where water has not been consumed.

If excluding any tenant spaces from this prerequisite (per the 10% tenant space exclusion), clearly indicate which spaces have been excluded in your project documentation. If using this exception, the tenant water use must be sub-metered and excluded from the consumption data for the prerequisite."

Delete "Also input your weighted occupancy and weighted operating hours (see Appendix A. Project Information) via the USGBC calculator."

Add the following on to the end of Step 4: "The water score will be calculated using the floor area, occupancy, and weekly operating hours information provided for the project. (see Definitions)."

Revise Required Documentation to read as:
"- Utility bills for all water sources, with consumption values and dates highlighted
o Internal meter reading logs may be provided in place of utility invoices where the latter are not applicable, but a narrative should be provided to explain the
circumstances (e.g., the building does not have utility meters and water consumption is measured with building-owned meters).
- Indicate how water used for irrigation is accounted for and whether this water use is included in the main building water meter.
- Water performance score result. A minimum performance score of 40/100 is required for initial certification."

Campus Applicable
No
Internationally Applicable:
No
4/9/2019Updated: 4/9/2019
Rating System Correction
Description of change:
Add "(Required)" after the 40 point threshold
Campus Applicable
No
Internationally Applicable:
No
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Ackerstein Sustainability, LLC
Principal

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USGBC logo

© Copyright U.S. Green Building Council, Inc. All rights reserved.

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:
  1. Annual water consumption (gallons), with monthly or daily totals
  2. Gross floor area (sq. ft. or sq. m.)
  3. Weighted occupancy
  4. 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.

In the end, LEED is all about documentation. LEEDuser’s Documentation Toolkit, for premium members only, saves you time and helps you avoid mistakes with:

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  • Sample templates to help guide your narratives and LEED Online submissions.
  • Examples of actual submissions from certified LEED projects.

LEEDuser expert

Dan Ackerstein

Ackerstein Sustainability, LLC
Principal

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