Whole Project Water Use Reduction | U.S. Green Building Council
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LEED BD+C: New Construction | v4 - LEED v4

Whole Project Water Use Reduction

Possible 10 points


To reduce indoor and outdoor water consumption of the entire project.


Depending on the building type and use, LEED may not currently address all the water use with-in the project boundary. This performance pathway for water conservation uses a whole project/ whole campus water budget approach. It allows projects to quantify water use with whole-building water balance modeling, similar to the compliance path for whole-building energy mod-eling. It also allows projects to include potentially significant water savings that previously went unrecognized, such as process water. This alternative compliance path (ACP) documents over-all water consumption reduction and establishes point thresholds based on this performance metric.

NOTE: A phone call must be conducted with GBCI reviewers prior to using this Pilot ACP. After you register the project for this ACP, you will be contacted for a call. The call must be completed before application, and the meeting notes must be uploaded into LEED Online.


Projects must document compliance with all Water Efficiency (WE) prerequisites separately. This ACP replaces the points available cumulatively in WE credits Outdoor Water Use Reduction, Indoor Water Use Reduction, and Cooling Tower Water Use. WEc Water Metering may be pursued separately.

To pursue this pathway, project teams must develop a water use baseline and create a proposed use model. Points are achieved based on reductions from the baseline, as follows:

Table 1. Points for reducing overall project water use

Percentage reduction


(New Construction, Core & Shell, Healthcare, Data
Centers, Hospitality, Warehouses & Distribution


(Schools, Retail)































Detailed Methodology and Documentation;
Create a baseline Water Balance Model

  • The baseline water balance model must represent all water sources and uses typically associated with the project type, location, building, and site.
    • Typical sources are potable water from municipal systems or wells. Municipally-treated seawater should also be included if this is a typical water source for the project’s region.
  • Demonstrate that the baseline meets:
    • Local building codes for water quality and efficiencies.
    • Industrial water consumption meets specific industrial standards established by the American Society for Testing and Materials (ASTM), International Organization for Standardization (ISO), American Water Works Association (AWWA) standards, United States Pharmacopoeia (USP), the Clinical and Laboratory Standards Institute (CLSI) or other industry-specific water quality and consumption standards.
  • Illustrate the average amount of water used for each type of equipment to determine an appropriate baseline.

Create a proposed Water Balance Model

  • The proposed water balance must represent all water sources and proposed water sources for the project building and site.
    • Water sources could include rainwater harvesting, greywater, black water treatment, process water reuse, air handler condensate, retention ponds, municipal water, well water, etc.
    • Water uses must align with those outlined in the baseline model.
    • Rainwater harvesting sources should include documentation from local weather stations providing hourly or daily precipitation amounts. In the United States of America, Puerto Rico, the US Virgin Islands, and various Pacific Islands, hourly precipitation data for over 5,000 weather stations are available here or here.
  • Illustrate the average amount of water used for each type of equipment to demonstrate that the proposed increased efficiency, compared to the baseline, exceeds the minimum threshold.

When calculating the baseline and proposed Water Balance Models:

  • Use existing LEEDv4 Building Design and Construction credit calculation methodologies where applicable. These credits include:
    • Rainwater Management – use calculation guidance when determining available stormwater for alternative uses in the proposed water balance.
    • Outdoor Water Use Reduction – use the credit guidance (which could include the EPA WaterSense Water Budget tool) to determine baseline and proposed water balances for outdoor water use.
    • Indoor Water Use Reduction – use the LEED guidance for frequency of use and defaults (for fixtures, fittings, site water, process, etc) for the baseline and proposed water balances.
    • Note: the requirements in the Cooling Tower Water Use credit do not provide a methodology for calculating water use of cooling towers, as the credit addresses filtration parameters and number of cycles. However, water used by cooling towers must be included in the baseline and proposed models.
  • Document water use for each water using component of the project in 1000’s gallons (k-gallons) or kiloliters (k-liters) per year.
  • All types of water use which constitute 5% or greater of the overall water demand must be illustrated in the model. Any individual uses that constitute less than 5% of the total demand may be excluded. However, the model must account for at least 90% of the total project water consumption. For example, a project’s overall water demand is 6,350 k-gal per year. There are 400 toilets within the scope of the project. The combined annual water use of all the toilets together equals 520 k-gal, which is 8.2% of the project’s overall water demand. Thus, this type of water use must be illustrated in the model. These toilets cannot be separated out into smaller groups that make up less than the 5% threshold. Provide clear justification in the documentation to support any exclusion(s).
  • Water uses could include, but are not limited to: fixtures and fittings, hot water, appliances (washing machines, dish washers, drinking fountains, ice makers), commercial kitchen equipment, process water (sterilizers, swimming pools, manufacturing process) HVAC (steam plants, cooling towers, humidification systems), landscape irrigation, etc.
  • Water demand and alternative source data should ideally be modeled on an hourly basis, but no greater than daily, to account for fluctuations in water demand and available supply. Extrapolation of data is acceptable if daily data is not available.



Register for the pilot credit

Credit Survey

To document water baselines and efficiency measures, provide one of the following:

  • For projects establishing a new baseline technology as the industry standard, submit exceptional calculations and at least one of the following:
    • List of three projects built in the last five years that use the baseline technology
    • Current utility incentive programs for new construction that establish the baseline
    • Published studies justifying the baseline technology as standard practice
  • For projects with proprietary manufacturing processes, demonstrate that the production process is more efficient than the company’s average production efficiency:
    • Identify at least three projects built in the last five years that manufacture the product
    • Calculate the process’s past average Water Consumption Index (WCI) in units of water per product manufactured to establish the baseline production efficiency
    • Provide the new process’s estimated WCI, anticipated production level, and an explanation of how these numbers were determined
    • Calculate the annual production process water cost savings using the baseline WCI, proposed WCI, and anticipated production level
  • Provide a diagram and narrative explaining the water balance and how the baseline and proposed water balances were developed. The narrative must describe what water conservation measures were used to reduce potable water use. Also, describe risk management measures that will be implemented to ensure that the water conservation measures will not lead to compromised water quality, poor Indoor Environmental Quality, or occupant health risks. ASHRAE Standard 188-2015, as an example, establishes minimum legionellosis risk management requirements for building water systems.

    Provide manufacturer specification documentation (i.e. cut sheets) or other data showing water usage of indoor and outdoor equipment used. In cases where the manufacturer’s information provides a range of performance values, use the most conservative value.

    Resources for Calculating the Water Balance

    Simulating Water: Supply and Demand in the Built Environment by Fred Betz and Willa Kuh presented at the 2014 ASHREA/IBPSA-USA Building Simulation Conference, September 10-12, 2014

    Public Review Draft or Approved (depending on timing) BSR/ASHRAE/USGBC/ASPE/AWWA Standard 191P Standard for the Efficient Use of Water in Building, Site and Mechanical Systems

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