Introduction

Water is one of our most precious resources, and its responsible management has become increasingly important as the world faces growing water scarcity issues. The LEED (Leadership in Energy and Environmental Design) rating system developed by the U.S. Green Building Council (USGBC) recognizes this challenge and offers a Water Efficiency (WE) credit category to encourage sustainable water practices in building design, construction, and operation. In this article, we’ll explore the key aspects of the LEED WE credits and learn how projects can earn these valuable points.

LEED Water Efficiency Credits Overview

LEED’s Water Efficiency credits are designed to promote the reduction of potable water use, both indoors and outdoors, as well as encourage the use of alternative water sources. The credits are divided into three main categories:

1. Outdoor Water Use Reduction
2. Indoor Water Use Reduction
3. Cooling Tower Water Use

Each of these categories offers points based on specific performance requirements and strategies that help reduce water consumption in different areas of a building project.

Outdoor Water Use Reduction

To earn points for outdoor water use reduction, projects must implement landscape designs that minimize potable water consumption. Strategies include using native or adapted plant species, installing high-efficiency irrigation systems, and utilizing alternative water sources like rainwater or graywater for irrigation.

Indoor Water Use Reduction

Indoor water use reduction credits are earned by implementing strategies that minimize potable water consumption in a building’s plumbing fixtures and fittings. Projects can achieve this by installing high-efficiency fixtures such as low-flow faucets, dual-flush toilets, and waterless urinals. Additional points can be earned by exceeding the baseline reduction percentages set by LEED.

Cooling Tower Water Use

For projects that use cooling towers, the Cooling Tower Water Use credit encourages optimization of water consumption by setting a minimum number of cycles of concentration and promoting the use of alternative water sources like rainwater or graywater.

LEED CS and NC Water Efficiency Credits Table

Requirement	New Construction (NC)	Core and Shell (CS)
Option 1: No Irrigation Required	X	X
Option 2: Reduced Irrigation	X	X

Requirements:

• New Construction (NC)
• Core and Shell (CS)

Reduce outdoor water use through one of the following options. Nonvegetated surfaces, such as permeable or impermeable pavement, should be excluded from the landscape area calculations. Athletic fields and playgrounds (if vegetated) and food gardens may be included or excluded at the project.

Option 1: No Irrigation Required Show that the landscape does not require a permanent irrigation system beyond a maximum two-year establishment period.

OR

Option 2: Reduced Irrigation Reduce the irrigation water consumption by improving the irrigation system efficiency, as calculated by the Environmental Protection Agency (EPA) WaterSense Water Budget Tool.

Guidance: There are no substantive changes to the prerequisite requirements; refer to the LEED v4 reference guide, with the following addition:

Further Explanation

Connection to Ongoing Performance

• LEED O+M WE credit Water Performance: Designing out the need for a permanent irrigation system, selecting native or adapted plants for project landscaping, and/or installing efficient irrigation systems reduces irrigation water use throughout the building life cycle, which may contribute to achieving the LEED O+M WE credit Water Performance.

Achieving LEED Water Efficiency credits requires a comprehensive approach that addresses outdoor and indoor water use reduction, as well as water use in cooling tower systems. Here’s a step-by-step procedure to help you comply with LEED Water Efficiency credits:

1. Understand the LEED Water Efficiency credit requirements: Familiarize yourself with the credit categories and specific requirements, such as outdoor water use reduction, indoor water use reduction, and cooling tower water use.
2. Assess the project’s water consumption baseline: Determine the baseline water consumption for your project based on the building type, location, and water use patterns. The EPA WaterSense Water Budget Tool can be a useful resource for this.
3. Develop a water efficiency strategy: Create a comprehensive water efficiency strategy that addresses all aspects of water use in your project. Consider the following areas:
   • Landscape design
   • Irrigation systems
   • Plumbing fixtures and fittings
   • Cooling tower systems
4. Outdoor water use reduction: a. Option 1 – No Irrigation Required: i. Select native or adapted plants that require little to no irrigation. ii. Design the landscape to not require a permanent irrigation system beyond a maximum two-year establishment period. b. Option 2 – Reduced Irrigation: i. Incorporate high-efficiency irrigation systems, such as drip irrigation or weather-based controllers. ii. Use alternative water sources, such as rainwater, graywater, or reclaimed water for irrigation. iii. Calculate the reduction in irrigation water use and ensure it meets or exceeds the required threshold.
5. Indoor water use reduction: a. Select and install high-efficiency plumbing fixtures, such as low-flow faucets, dual-flush toilets, and waterless urinals. b. Calculate the reduction in indoor water use and ensure it meets or exceeds the required threshold.
6. Cooling tower water use: a. Optimize cooling tower water consumption by increasing the number of cycles of concentration. b. Use alternative water sources, such as rainwater or graywater, in cooling tower systems.
7. Documentation and submission: a. Prepare the necessary documentation, including calculations, product specifications, and design plans that demonstrate compliance with the LEED Water Efficiency credit requirements. b. Submit the documentation to the USGBC for review and approval.
8. Monitor and maintain water efficiency performance: Once the project is completed and occupied, regularly monitor water consumption to ensure ongoing performance. Implement a water management plan to maintain and improve water efficiency over time.

By following this step-by-step procedure, you can successfully comply with LEED Water Efficiency credit requirements and make a positive impact on water conservation in your building project.

LEED Water Efficiency Credit Document Requirements Table for LEED NC and LEED CS

Requirement/Document	New Construction (NC)	Core and Shell (CS)
Landscape Plan	X	X
Plant List (native or adapted species)	X	X
Irrigation Plan (if applicable)	X	X
Irrigation System Specifications	X	X
Two-year Establishment Period Statement	X	X
EPA WaterSense Water Budget Tool Results	X	X

To calculate the outdoor water use reduction for LEED compliance, you’ll need to compare the landscape water requirement of your project’s landscape design to a baseline established using the Environmental Protection Agency (EPA) WaterSense Water Budget Tool. Here’s a sample calculation for a small office building with a landscaped area.

Site characteristics:

Landscape area: 5,000 sq. ft (464.5 sq. m)
Irrigation efficiency: 0.75 (assumed, as per LEED requirements)
Baseline water use (using EPA WaterSense Water Budget Tool):

Baseline Landscape Water Requirement (LWR) = 100,000 gallons per year (378,541 liters per year)
Project landscape design:

Plant species: A combination of native and adapted plants with low water requirements
Irrigation system: Drip irrigation with a smart controller (weather-based)
Option 1: No Irrigation Required

If the landscape does not require a permanent irrigation system beyond a maximum two-year establishment period, the project would achieve 100% outdoor water use reduction. However, for this example, we’ll assume that some irrigation is still required.
Option 2: Reduced Irrigation

Reduced Landscape Water Requirement (LWR) = 60,000 gallons per year (227,125 liters per year)
Percentage reduction in outdoor water use:

(100,000 – 60,000) / 100,000 = 0.4

Outdoor water use reduction = 40%

LEED Credit Compliance Narrative:

The project has successfully achieved a 40% reduction in outdoor water use compared to the baseline established using the EPA WaterSense Water Budget Tool. The landscape design features native and adapted plants with low water requirements, and a drip irrigation system with a smart controller has been installed to optimize water use. The outdoor water use reduction surpasses the minimum requirement of 30% for the LEED Outdoor Water Use Reduction credit under the Water Efficiency category for both LEED NC and LEED CS. As a result, the project is in compliance with the LEED requirements for this credit and contributes to a more sustainable and water-efficient built environment.

Requirements:

• New Construction (NC)
• Core and Shell (CS)

Reduce outdoor water use through one of the following options. Nonvegetated surfaces, such as permeable or impermeable pavement, should be excluded from the landscape area calculations. Athletic fields and playgrounds (if vegetated) and food gardens may be included or excluded at the project.

Option 1: No Irrigation Required Show that the landscape does not require a permanent irrigation system beyond a maximum two-year establishment period.

OR

Option 2: Reduced Irrigation Reduce the irrigation water consumption by improving the irrigation system efficiency, as calculated by the Environmental Protection Agency (EPA) WaterSense Water Budget Tool.

Guidance: There are no substantive changes to the prerequisite requirements; refer to the LEED v4 reference guide, with the following addition:

Further Explanation

Connection to Ongoing Performance

• LEED O+M WE credit Water Performance: Designing out the need for a permanent irrigation system, selecting native or adapted plants for project landscaping, and/or installing efficient irrigation systems reduces irrigation water use throughout the building life cycle, which may contribute to achieving the LEED O+M WE credit Water Performance

Quiz: Test Your Knowledge on LEED Water Efficiency Credits

What does LEED stand for?
a) Leading Efficiency and Environmental Design
b) Leadership in Energy and Environmental Design
c) Leaders in Environmental Efficiency and Design
d) Low Energy and Environment Development
Answer: b) Leadership in Energy and Environmental Design

How many main categories are there in the LEED Water Efficiency credits?
a) 2
b) 3
c) 4
d) 5
Answer: b) 3

Which of the following is NOT a category in the LEED Water Efficiency credits?
a) Outdoor Water Use Reduction
b) Indoor Water Use Reduction
c) Energy Use Reduction
d) Cooling Tower Water Use
Answer: c) Energy Use Reduction

What is one strategy to earn points for outdoor water use reduction?
a) Installing solar panels
b) Using native or adapted plant species
c) Insulating hot water pipes
d) Replacing light fixtures with LED lights
Answer: b) Using native or adapted plant species

How can projects reduce indoor water use?
a) By installing high-efficiency plumbing fixtures
b) By improving insulation
c) By using recycled building materials
d) By optimizing HVAC systems
Answer: a) By installing high-efficiency plumbing fixtures

Which alternative water source can be used for irrigation?
a) Drinking water
b) Rainwater
c) Pool water
d) Sea water
Answer: b) Rainwater

What is the primary goal of LEED Water Efficiency credits?
a) To increase energy efficiency
b) To reduce potable water consumption
c) To improve indoor air quality
d) To reduce greenhouse gas emissions
Answer: b) To reduce potable water