Water efficiency changes for LEED 2012
By Winston Huff, CPD, LEED AP BD+C
The USGBC LEED rating system is a guideline for building teams wanting to design, build and operate sustainable buildings that reduce energy and water consumption when compared to “average” buildings through the use of sustainable site, materials and resources practices. The LEED rating system offers a checklist of sustainable elements, called credits, which can be used in a building. The more credits that a building team earns, the higher the sustainable rating is for the building.
Later this year the LEED rating system will be updated for 2012. I am a member of the Technical Advisory Group (TAG) responsible for the revision. We have worked for several years to develop the new water-efficiency prerequisites and credits that will be included in LEED 2012. During our first meetings, we discussed what future sustainable buildings would look like to determine what the rating system should require.
We debated initiatives such as the 2030 Challenge, which aims for all new buildings to be net zero energy or carbon neutral by the year 2030. At what point in the future should LEED Platinum-rated buildings be required to be net zero energy? Is net zero energy the ultimate goal of sustainable buildings? What about beyond net zero? Current thinking is that a truly sustainable building should go beyond net zero energy and be regenerative or be able to produce enough energy on site to supply surrounding buildings.
Energy use is an important consideration, but what about water? In the future, buildings could be net zero water and even regenerative water. Future buildings could be self-sufficient, with few or no connections to the municipal water system. Similar to energy systems, a water-regenerative system could collect, filter and monitor water inside the building as well as supply other buildings around it to help them be net zero water.
All of these topics are interesting concepts to discuss, and it is a great exercise to look at the possibilities for future buildings. For now, however, LEED 2012 must consider real-world technologies and strategies that are currently in the marketplace, while keeping the future goals in mind. It also must include some challenges to help the industry expand and incorporate new strategies into building designs. The end result, from a water viewpoint, is that the 2012 revision can make significant reductions in water consumption in LEED-certified buildings. More water systems are included in the guidelines, and more credits are available for water efficiency.
Draft copies of the proposed guidelines are available on the USGBC website (usgbc.org). The new version is scheduled to be introduced this November at the Greenbuild conference in San Francisco. New copies and educational materials will be available at that time as well.
The intent of this article is to provide an overview of LEED 2012 from a water perspective. For more detail, refer to the draft guidelines. Changes in the credits will be made to all of the rating systems, including Building Design and Construction, Existing Buildings, Operations and Maintenance and Healthcare. The goal was to simplify the WE (Water Efficiency) credits and to address the different water users in a building.
Outdoor water use reduction
The largest irrigated crop in the United States is turf grass. Large amounts of drinking-quality water are used to irrigate lawns, golf courses, landscapes and more (Figure 1). To address this concern, the outdoor water use reduction prerequisite and credits are simpler to follow and now use the Landscape Water Requirement (LWR) as calculated by the EPA WaterSense Water Budget tool.
The credit encourages facilities to design and install landscaping that does not require irrigation. If a building does require irrigation, the guidelines encourage designs that reduce the amount of water used in the irrigation system. Better irrigation controls and collecting alternate water (using rainwater harvesting, for example) can reduce the amount of water the facility uses for irrigation.
The exclusions for outdoor water include non-vegetated surfaces, athletic fields, playgrounds and food gardens.
Requirement reduction: A fundamental question has to be considered: If alternative water is used in the irrigation system and municipal water use is reduced, does a site still need to use efficient systems? For example, can buildings that have access to plenty of rainwater and use little municipal water still be considered sustainable if the irrigation system uses large amounts of the harvested water? Should the USGBC certify a building that has inefficient irrigation?
A sustainable building should use less water and should use the water it does have efficiently. This is why a facility should obtain one point by reducing the landscape water first through water-reduction measures. For example, plant species selection and irrigation system efficiency should be used on all sustainable buildings whether they have alternate water or not. Additional water-efficiency measures beyond the required reduction measures can be from alternate water sources.
Alternate water: Alternate water systems are encouraged in the credits and can include rainwater harvesting, air-conditioning condensate and other sources of onsite water. The design and construction teams, owner and property management should look at alternative water systems as a water source early on in a project. Then the team can decide if the water is best used for irrigation, process water, graywater, mechanical or some other water supply for the facility.
Metering: Water metering is encouraged in many of the Water Efficiency credits, including the outside water credits. Studies have shown that the installation of water meters reduces water usage. The meter itself does not reduce water usage; it measures the way water is used. Water meters show the operator when and where leaks are occurring and track water use patterns. The end result is that the facility operator has a tool to run the water system efficiently.
Indoor water use reduction
This credit covers the plumbing fixtures, which are an important part of water efficiency. The prerequisite in LEED 2012 is the same: Fixtures must be 20 percent more efficient than the baseline. Obviously, using more efficient fixtures can increase the number of credits for a facility.
Similar to the outdoor water use section, a question could arise. What if a building used alternate water for the plumbing flush fixtures and little or no municipal water? Can a sustainable building use inefficient fixtures even if the building uses alternative water? For example, should a building that uses harvested rainwater to flush fixtures be allowed to use inefficient water closets and urinals? Can this building be considered sustainable?
The intent is that a sustainable building should have a core concept of efficiency and consider all water use both on and off site. Even though it obtained credits by using alternate water sources, a building would not be considered sustainable if that water was not used efficiently.
A criticism of past versions of LEED is that they did not include other systems in a building that use water. For 2012, process water and appliances are now included in all of the rating systems. The process and appliance section includes the other interior systems that use water such as clothes washers and dishwashers. These systems can be large water consumers in residential buildings and food service facilities.
Building-level water metering
The water industry lacks water use data to serve as a baseline in different types of buildings such as healthcare and food service facilities. LEED 2012 includes a building-level water meter prerequisite intended to help building owners monitor water use and provide data to the USGBC so they can develop a better database.
The intent of the credit is to provide accurate water consumption patterns to support operations and identify opportunities for additional water-saving practices. Similar to the outdoor credit, water meters and a monitoring system will help operations identify problems and develop solutions for the facility’s water consumption. Metering includes irrigation, plumbing fixtures, domestic hot water, reclaimed water and mechanical uses.
Cooling towers use large amounts of water in buildings. LEED 2012 requires basic equipment for the prerequisite, including makeup and blowdown meters, conductivity controllers and overflow alarms. Drift is a concern where water is sprayed into a tower and cross winds can blow the water out of the tower. To address this issue, the towers are now required to have drift eliminators.
Again, the prerequisite requires an efficient baseline for the cooling tower system. If a building uses alternate water sources, it could not be a sustainable building if it did not use that water efficiently.
The prerequisite covers the hardware items of the cooling tower. The credit involves the operations of the cooling tower system. Installing certain features in a cooling tower can reduce water usage but does not guarantee that the total system will use less water. Proper operation of the system and using the tools that are available to the operations staff are necessary to reduce total water usage.
The water in a cooling tower system must be treated and maintained. The source water can be hard or soft depending on the quality of the available water, and the cooling tower is open to the atmosphere, requiring methods to prevent biological contaminants from entering the water loop. As the water evaporates, the treatment residue will concentrate in the remaining water, requiring the water to be “blown down” and replaced with fresh water. The LEED credit is intended to encourage operators to reduce the frequency of blowdown; as a result, the overall system will use less water.
As mentioned, alternate water can be used as cooling tower makeup to help obtain this credit. Building teams are looking at alternate ways to capture rainwater or air-conditioning condensate to use in facility cooling towers.
The intent of this reworked credit is to increase the efficiency of wastewater reuse by encouraging water reuse, reduction or recovery. The way the credit is restructured should encourage design teams to develop alternate water systems. Technologies recently introduced have increased the availability of these systems to project teams. New standards are now available for these systems, including NSF 350: Onsite Residential and Commercial Reuse Treatment Systems.
The new and restructured Water Efficiency credits in LEED 2012 introduce new areas such as process water and cooling towers that can be developed in future rating systems to further reduce water usage in a facility. They set the groundwork to promote the importance of water efficiency in sustainable buildings. Just because a building with inefficient systems and fixtures uses alternate water does not mean it should be considered a sustainable building. Efficiency should be an important first goal in all sustainable buildings.
Alternate water systems should continue to be an important part of sustainable buildings. Future buildings should not use drinking-quality water for their non-drinking water systems. Reducing the amount of municipal water used in a building also will help communities use less energy and reduce the strain on old water infrastructures.
Collecting rainwater on site can reduce rainwater flows downstream while also reducing the amount of water used from municipal systems. LEED 2012 is an important step in incorporating these issues in today’s buildings.
Winston Huff, CPD, LEED AP BD+C, is a project manager, plumbing fire protection designer and sustainable coordinator with Smith Seckman Reed Consulting Engineers in Nashville, Tenn. He serves as an ASPE representative on the ICC Green Construction, Energy and Water Code Development Committee and is on the U.S. Green Building Council’s Water Efficiency Technical Advisory Group. He was the founding editor of Life Support and Biosphere Science and has served as its editor-in-chief. He also is editor of Me Green You Green (megreenyougreen.com), a LEED credit databank.