WE Prerequisite 1: Water Use Reduction- 20% less than standard.
WE Credit 1: Water Efficient Landscaping 2–4 Points
WE Credit 3: Water Use Reduction (30-40% reduction) 2-4 Points
Intent- To increase water efficiency within buildings to reduce the burden on municipal water supply and wastewater systems.
By: Wesley Holmes
Energy Efficient Bathrooms in the LEED Certified APUS Academic Center from Kudda on Vimeo.
Between 1950 and 2000, the U.S. population nearly doubled. In that same period water consumption more than tripled to 410 billion gallons per day (Bgal/d) in 2005, according to the US Geological Survey (USGS). Thermoelectric power generation and irrigation are by far the largest consumers of national water supply, consuming 201 Bgal/d and 128 Bgal/d in 2005, respectively. In the same year public water supply, utilized by 86% of the population, accounted for 44.2 Bgal/d. On average an individual will use 100 gallons of water each day—enough to fill 1,600 drinking glasses. This level of consumption is costly. The 2009 EPA Building Impact Summary notes that $4 billion is spent annually in the U.S. for energy to run drinking water and wastewater utilities. If this could be reduced by just 10 percent through better efficiency, that could save $400 million a year. Here, we will look at APUS efforts to reduce water consumption in the new Academic Center.
The Whole Building Design Guide advises that building owners and developers incorporate efficient water conservation strategies throughout the planning and commissioning process. The USGBC recommends low flow water fixtures and efficient landscape designs to make the most impact on water consumption and waste. Throughout the development of the Academic Center, APUS has remained conscientious of water savings and water quality. In the sites development the university emphasized rainwater runoff quantity and quality controls. For landscaping needs, APUS elected to use native plants. Native plants are adapted to the areas natural rainfall and require little or no additional water. The sites small beds and indigenous plants will utilize no potable water for landscape irrigation and allow the university to pursue WEc1 for four points.
For domestic and commercial buildings, landscape irrigation is a small portion of the annual water use. Most water is consumed through our sinks, showers and toilets. APUS has focused on using high efficiency water fixtures to reduce long term consumption. More than 1 trillion gallons of water pass through faucets across the United States each year and a leaky faucet can waste gallons of water in a short period of time. Academic Center faucets put out .5 gallons per minute (gpm) per sink. Showering is another heavy water consumer, accounting for approximately 17 percent of residential indoor water use in the United States—more than 1.2 trillion gallons of water consumed each year. The AC will have shower facilities to accommodate bicycle commuters. Showers will have a low flow of 1.5 gpm compared to the standard 2.5 gpm. Toilets are the other top water consumers. A leaky toilet can waste 200 gallons per day. The AC will utilize low flow urinals and dual flush toilets to reduce waste water. Urinals will have a flush of just half a liter, that’s one quarter of a two liter soda bottle, compared to the standard gallon. The dual flush toilets offer the user two flushing options, a low flow flush of 1.1 gallons and the standard flush of 1.6 gallons.
To ensure that the design meets the desired performance, KTD Engineers, the same firm responsible for the buildings energy modeling, modeled the building water performance. Water use can be modeled using the same type of software that is used to model energy consumption. Manipulating fixtures in the model, KTD was able to help APUS find strategies to reduce water consumption possibly beyond the benchmarks set by the USGBC. The LEED rating system sets a baseline standard (WEp1) that buildings seeking certification must use 20% less water than a standard building of the same size. Owners and developers can go beyond this requirement and pursue 2-4 more points for achieving 30-40% water use reductions (WEc3), respectively. The base building design, without water efficiency features, was modeled to show a consumption rate of 199,302 gallons per year. When the buildings water efficiency features were added to the model it showed savings of 47% below this standard, reducing consumption by 94,270 gallons per year. Last week, APUS decided to push it a little further by upgrading to even higher efficiency fixtures. The AC is now projecting water savings of over 50%, amounting to 100,030 gallons of potable water saved each year.
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