LEED v4 Updates to Water Efficiency Credit Category

The impacts of severe drought, as defined by the U.S. Drought Monitor, include common water shortages, water restrictions and crop and pasture losses. At any time during the past five years, on average, 20% of the contiguous United States was experiencing these severe drought conditions.

During the summer of 2012, this statistic peaked at over 46%. According to data published by the U.S. Drought Monitor last week, over 55% of California is currently experiencing conditions of exceptional drought, the effects of which include “exceptional and widespread crop and pasture losses and shortages of water in reservoirs, streams and wells creating water emergencies.2”

LEED addresses drought through the Water Efficiency credit category. The idea is that, if drought conditions are to persist or worsen, the best solution is to optimize the efficiency with which society uses the water it has.

Due to the commonality of drought conditions, both in the United States and worldwide, LEED v4 includes significant changes to the Water Efficiency credit category.

LEED v4 BD+C New Construction: Water Efficiency Credit Category

Requirements: LEED 2009’s BD+C: NC Water Efficiency credit category includes one requirement: Water Use Reduction. This prerequisite requires that the building’s water fixtures, including toilets, urinals, showerheads and faucets, use 20% less water than the baseline.

In contrast, LEED v4 BD+C: NC includes three prerequisites. The first, Indoor Water Use Reduction, is similar to LEED 2009’s Water Use Reduction requirement described above, but has a slightly larger scope (eg. It includes dish washers and clothes washers). The second, Outdoor Water Use Reduction, mandates that permanent irrigation be absent or reduced by a minimum of 30% from the baseline for the site’s peak watering month. The final requirement is Building-level Water Metering. The building must have permanent water meters that measure the total potable water use by the building and its grounds.

These requirements together specifically act to decrease the building’s water demand, thereby ensuring that the building and its grounds do not enhance local or regional drought conditions.

Modified Credits: Adapting LEED 2009 BD+C: NC Credits for LEED v4

The three additional credits offered as a part of LEED 2009 are designed to further decrease the building’s total water use. The principles behind all three were included, albeit modified, in LEED v4. LEED 2009’s Water Efficient Landscaping and Water Use Reduction credits were updated and replaced with credits titled Outdoor Water Use Reduction and Indoor Water Use Reduction. LEED 2009’s Innovative Wastewater Technology credit was eliminated, although its intent of reducing wastewater generation and potable water demand has been transferred across several of LEED v4’s credits.

New Credits in LEED v4

LEED v4 BD+C: NC includes two credits new to this category: Cooling Tower Water Use and Water Metering. The Cooling Tower Water Use credit mandates a decrease in the total water used by the cooling tower while also defining maximum acceptable levels for several common water quality parameters. The Water Metering credit is available for buildings that add meters to monitor the water use of two of the following: irrigation, indoor plumbing fixtures and fittings, domestic hot water, boiler water, reclaimed water and additional process water.

Design and Continued Use

As described above, LEED strengthened the BD+C: NC Water Efficiency credit category during the development of LEED v4. This credit category is critical as it addresses not only the initial design and construction of the building, but also provides a foundation for the building’s future water use.

In a time when drought conditions persist and the demands on water are increasing, LEED buildings that prioritize efficient water use can be an important tool in the development of society’s sustainable water use plan.

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Note: Information regarding the Water Efficiency credit category was obtained from USGBC.org.

1 The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.

For a comparative look at how other rating systems for sustainable design, such as Living Building Challenge and Green Globes, compare to LEED v4 in the water efficiency category, see this article.