Quick Tip with Outdoor Water documentation

The Green Building Team on January 6, 2023

Rating System/Standard
LEED v4.1
Certification essentials

Under LEED v4/v4.1 BD+C WE Outdoor Water Use Reduction, Option 2 on reducing irrigation, project teams have the choice of using either the USGBC Outdoor Water Use Reduction Calculator or the EPA WaterSense Water Budget Tool (for which Canadian postal codes can be entered). Both provide the values to be entered into the LEED Form.

For those using the USGBC calculator, it is easy to misinterpret which values need to be entered into the LEED Form. This impacts projects that are claiming additional reductions through alternative water sources and smart scheduling technologies.

As you can see below, the Form requires the Landscape Water Allowance value and the Landscape Water Requirement.

The Landscape Water Requirement is the designed water use and found on the Summary tab of the calculator – easy.
The Landscape Water Allowance is the watering requirement that the project needs to meet to obtain the prerequisite. In other words, it is the maximum volume of water the project can use. The Landscape Water Allowance is not found in the Summary tab. Instead, you’ll find it on the Baseline Calculation tab in the calculator as shown below.

The Landscape Water Baseline represents the baseline water needs in the peak watering month and is a value shown in the Summary tab of the calculator. This value is not transcribed to the LEED Form as it has already been accounted for in the percentage shown on the Summary tab, and that percentage is transcribed to the LEED Form to demonstrate compliance with prerequisite. The previously mentioned Landscape Water Allowance is a 30% reduction from this baseline, the minimum requirement necessary to meet the prerequisite.

The reason for use of the Landscape Water Allowance in the Form’s calculation is because the further reductions with smart scheduling and alternative water to achieve points are calculated from the Landscape Water Allowance, and not the Landscape Water Baseline.

Note that in the LEED v4 BD+C Reference Guide, under the credit’s Step-by-Step Guidance, the Landscaped Water Allowance is referred to as the “Prerequisite Landscape Water Requirement”.