Indoor water use reduction is an essential aspect of sustainable building design, particularly for commercial buildings where water consumption can be significant. The LEED (Leadership in Energy and Environmental Design) rating system, developed by the U.S. Green Building Council (USGBC), offers a credit category for Indoor Water Use Reduction to promote water-efficient practices in new commercial construction (NC) and core and shell (CS) projects. In this article, we will explore the key aspects of the LEED Indoor Water Use Reduction credit and provide guidance on achieving this credit for LEED NC and CS projects.

Indoor Water Use Reduction LEED Credit

The Indoor Water Use Reduction credit aims to promote water conservation and reduce the consumption of potable water in buildings by encouraging the installation of high-efficiency plumbing fixtures and fittings. To earn this credit, projects must demonstrate a reduction in indoor water use compared to a calculated baseline, which is determined by the building type and occupancy.

Strategies for Indoor Water Use Reduction

Install high-efficiency plumbing fixtures and fittings: Select and install high-efficiency toilets, urinals, faucets, and showerheads that meet or exceed the EPA WaterSense standards. These fixtures use less water without compromising performance.

Implement water-efficient appliances: Choose water-efficient dishwashers, washing machines, and other water-consuming appliances that have earned the ENERGY STAR label.

Monitor and control water use: Incorporate submetering systems to track water consumption and identify potential areas for improvement. Regular monitoring enables building operators to detect leaks and address issues promptly.

Educate occupants: Encourage water-saving behaviors among building occupants by providing information and resources on water conservation strategies.

Quiz: Test Your Knowledge on Indoor Water Use Reduction LEED Credit

What is the primary goal of the Indoor Water Use Reduction LEED credit?
a) To reduce energy consumption
b) To decrease indoor air pollution
c) To minimize potable water use
d) To enhance occupant comfort
Answer: c) To minimize potable water use

Which plumbing fixture is NOT a part of the Indoor Water Use Reduction LEED credit?
a) Dual-flush toilet
b) Low-flow faucet
c) Waterless urinal
d) High-efficiency air conditioner
Answer: d) High-efficiency air conditioner

What organization sets the standards for high-efficiency plumbing fixtures?
a) U.S. Green Building Council
b) Environmental Protection Agency
c) Department of Energy
d) International Plumbing Code
Answer: b) Environmental Protection Agency

Which appliance label indicates water efficiency?
a) WaterSense
b) ENERGY STAR
c) Green Seal
d) LEED Certified
Answer: b) ENERGY STAR

LEED Indoor Water Use Reduction Credit Document Requirements Table

Requirement/Document	New Construction (NC)	Core and Shell (CS)
Plumbing fixture and fitting specifications	X	X
Water use calculations	X	X
Submetering plan (if applicable)	X	X
Occupant education materials	X	X

Sample calculation for water use reduction

To calculate indoor water use reduction for LEED compliance in liters, you’ll need to convert the water use of your project’s plumbing fixtures and fittings to a baseline established by the Energy Policy Act of 1992 (EPAct 1992) and the Uniform Plumbing Code (UPC) or International Plumbing Code (IPC). Here’s a sample calculation for a small office building, with conversions from gallons to liters (1 gallon ≈ 3.78541 liters).

Baseline fixture performance requirements (liters per flush or liters per minute):

Water Closet (Toilet): 6.057 liters per flush (lpf)
Urinal: 3.785 liters per flush (lpf)
Lavatory Faucet (private use): 8.327 liters per minute (lpm)
Lavatory Faucet (public use): 1.893 liters per minute (lpm)
Showerhead: 9.464 liters per minute (lpm)
Building fixture count:

4 Water Closets
2 Urinals
4 Lavatory Faucets (private use)
4 Lavatory Faucets (public use)
2 Showerheads
Assumed daily usage per occupant:

Water Closet: 3 uses per day
Urinal: 2 uses per day
Lavatory Faucet (private use): 3 uses per day, 30 seconds per use
Lavatory Faucet (public use): 4 uses per day, 30 seconds per use
Showerhead: 1 use per day, 5 minutes per use
Total occupants: 20

Baseline daily water use:

Water Closets: 6.057 lpf * 3 uses * 20 occupants = 363.42 liters
Urinals: 3.785 lpf * 2 uses * 20 occupants = 151.4 liters
Lavatory Faucets (private use): 8.327 lpm * 3 uses * 20 occupants * 0.5 min/use = 249.81 liters
Lavatory Faucets (public use): 1.893 lpm * 4 uses * 20 occupants * 0.5 min/use = 75.72 liters
Showerheads: 9.464 lpm * 1 use * 20 occupants * 5 min/use = 946.4 liters
Total baseline daily water use = 363.42 + 151.4 + 249.81 + 75.72 + 946.4 = 1786.75 liters

Project fixture performance:

Water Closet (Toilet): 4.85 lpf (high-efficiency)
Urinal: 1.893 lpf (high-efficiency)
Lavatory Faucet (private use): 5.678 lpm (high-efficiency)
Lavatory Faucet (public use): 1.893 lpm (sensor-operated)
Showerhead: 7.571 lpm (high-efficiency)
Project daily water use:

Water Closets: 4.85 lpf * 3 uses * 20 occupants = 291 liters
Urinals: 1.893 lpf * 2 uses * 20 occupants = 75.72 liters
Lavatory Faucets (private use): 5.678 lpm * 3 uses * 20 occupants * 0.5 min/use = 170.34 liters
Lavatory Faucets (public use): 1.893 lpm * 4 uses * 20 occupants * 0.5 min/use = 75.72 liters
Showerheads: 7.571 lpm * 1 use *

To calculate the net water saved, we will subtract the project’s total daily water use from the baseline daily water use.

Total baseline daily water use = 1786.75 liters
Total project daily water use = 1376.4 liters

Net water saved = Baseline daily water use – Project daily water use
Net water saved = 1786.75 liters – 1376.4 liters
Net water saved = 410.35 liters

So, the net water saved per day is 410.35 liters.

To calculate the percentage savings in water use, we will divide the net water saved by the baseline daily water use and multiply the result by 100.

Percentage savings = (Net water saved / Baseline daily water use) * 100
Percentage savings = (410.35 liters / 1786.75 liters) * 100
Percentage savings ≈ 22.97%

The water use reduction achieved in this project is approximately 22.97%.

LEED Credit Compliance Narrative:

The project has successfully achieved a 22.97% reduction in indoor water use compared to the baseline established by the EPAct 1992 and UPC/IPC. High-efficiency plumbing fixtures and fittings were installed, including water closets, urinals, lavatory faucets (private and public use), and showerheads. The water use reduction surpasses the minimum requirement of 20% for the LEED Indoor Water Use Reduction credit under the Water Efficiency category. 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.

By following the strategies outlined in this article and meeting the document requirements, commercial buildings can successfully achieve the LEED Indoor Water Use Reduction credit, resulting in significant water savings and a more sustainable built environment.