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Everything You Need to Know About Water Use Intensity

Organizations across the country use a variety of metrics for tracking water. What does success look like when it comes to water use? While the answer is unique to every landscape, some general water truths are universal.

One of these is that water use intensity is a fundamental component of your overall water health. Whether you’re trying to achieve LEED certification, balance a budget, grow more sustainable, or improve your business health, you should have a handle on water use intensity.

So what is it, why is it so important, and how is yours doing? Let’s take a look.

What is Water Use Intensity?

Water Use Intensity (WUI) generally refers to the rate at which water is used in a given area. It is an indicator of how much water your building requires during its occupation. WUI informs sustainable water allocation.

Looking at WUI can give insight into how well your organization is managing water resources over time. WUI has far-reaching impact on areas like business performance, conservation frameworks, and how effectively a landscape is reducing pressure on the environment.

How is WUI measured?

WUI is calculated in gallons per square foot per year (gal/ft²/yr). There is a difference between indoor WUI and general WUI (from all water sources). Your WUI metrics aren’t generally adjusted for any of your property use details, like number of workers, weekly working hours, etc.

With general WUI, you would divide all water sources by a building’s square footage (excluding parking and irrigated areas).

Indoor WUI is slightly different. It divides all indoor water meters by the building’s square footage (again, excluding any parking and/or irrigated areas). The indoor WUI accounts for features like showers, toilets, kitchens, and lavatories, whose fixtures are critical to energy conservation and water use.

Why is WUI important for my business?

The WUI metric will help you discern whether you’re optimizing your water use. It also helps you calculate your yearly water use estimate, so you can track how you’re performing as the year gets underway. Staying on top of your WUI can help you fix problem areas faster, and save money before minor problems turn into catastrophes.

WUI is an easy way to compare water use across different types of buildings. There’s a wide variation in water use among different buildings. For example, buildings where people live and work – hotels, hospitals, and multi-family housing – will have the highest WUI.

I’ve calculated my WUI. Is the result good or bad?

If you’ve calculated your WUI, what should you do with that information? It can be overwhelming to come up with a number outside of any context for whether it’s high or low. Having a “good” WUI will depend on the type of organization in question, and the complexities of the water systems within it. To give you some benchmarks, here are the median WUIs for several common types of buildings, according to the EPA:

  • Senior Care Facility – 60 gal/ft²
  • Hotel – 55 gal/ft²
  • Hospital – 52 gal/ft²
  • Multifamily Housing – 45 gal/ft²
  • Residence Hall – 39 gal/ft²
  • Supermarket – 24 gal/ft²
  • Medical Office – 18 gal/ft²
  • Office – 13 gal/ft²
  • Financial Institution – 12 gal/ft²
  • Court House – 10 gal/ft²
  • K-12 School – 10 gal/ft²
  • House of Worship – 7 gal/ft²
  • Retail – 6 gal/ft²
  • Unrefrigerated Warehouse – 4 gal/ft²

What is the relationship between WUI and LEED?

Water use is an important part of the LEED certification process. The Leadership in Energy and Environmental Design (LEED) verifies that a building is operating according to optimal environmental design. Water efficiency is 10% to 15% of the assessment.

If you have an understanding of your WUI, you’re more likely to take steps to reduce both indoor and outdoor water use, as well as installing proper water meters that can analyze your water use for buildings and grounds.

Preparing for LEED certification and optimizing your WUI go hand-in-hand. For more information, check out our breakdown of water efficiency for LEED certification.

The Bottom Line….

 At a time when water is growing more scarce, its management requires both care and a sense of urgency. The WUI can impact your entire bottom line, from budgeting to regulatory compliance to future projections. No matter how you choose to assess your water use, make sure you factor in this important metric; it’s one number that can illustrate the entire story of your property’s water efficiency.