Constructing a net zero water building includes the following design elements:
- Reducing demand by employing innovative technologies that consume less water.
- Producing alternative water sources to offset purchased freshwater.
- Treating wastewater on-site and reuse or inject treated wastewater into the original water supply.
- Implementing green infrastructure by infiltrating stormwater to the original water supply.
An important tenet of net zero water design is incorporating water-efficient equipment and landscaping that substantially reduces the demand for water as illustrated in the table below.
High-Performance Design Options
|Plumbing||High-efficiency and the Environmental Protection Agency (EPA) WaterSense-labeled equipment||Specify the most efficient equipment available, consider non-water-using fixtures such as composting toilets and non-water urinals, ensure that proper operation and maintenance practices are established|
|Commercial kitchen||EPA WaterSense and ENERGY STAR-qualified equipment||Specify the most efficient equipment available, look for dishwashers that recycle water|
|Cooling and heating systems||High-efficiency system design||If applicable, reduce or eliminate water used for cooling and heating by using passive systems that use the power of the sun and natural convection cycles|
|Landscaping||Water-Smart landscaping||Incorporate water efficiency principles with native plantings that require no supplemental irrigation into the landscape design|
Successful Example Projects
- Seattle Bullitt Center successfully implemented composting toilets in an office building
- The EPA implemented native landscaping at several facilities
For More Information
- Federal Energy Management Program (FEMP) Best Management Practices (BMPs) for Water Efficiency
- EPA WaterSense at Work BMPs
- EPA WaterSense Water-Smart Landscaping Design Tips
Produce Alternative Water
Alternative water is a sustainable water source not derived from freshwater sources. Alternative water includes:
- Harvested rainwater, stormwater, or sump-pump (foundation) water
- Air cooling condensate
- Rejected water from water purification systems
- Reclaimed wastewater
- Water derived from other water reuse strategies.
Alternative water can be produced on-site or purchased in the form of reclaimed water from a local utility.
A net zero water building (or campus) uses alternative water sources to offset the use of freshwater. Freshwater is water sourced from surface or groundwater such as lakes and rivers. See FEMP's Alternative Water Sources Maps.
Alternative Water Source
|Harvested rainwater||Precipitation that is collected from a roof and stored for use.||Minimal treatment is needed for irrigation.|
|Harvested stormwater||Precipitation that is collected from hardscape on the building's grounds and stored for use.||Additional treatment is likely needed compared to rooftop rainwater because stormwater picks up contaminants from the hardscape.|
|Foundation water||Water that is pumped away from the building's foundation (also referred to as sump-pump water).||Treatment depends on the quality of the source.|
|On-site reclaimed wastewater||Wastewater that is discharged from buildings and is treated and stored for use.||Substantial filtration and disinfection is required.|
|Graywater||Lightly contaminated wastewater that is discharged from lavatory sinks, showers, and laundry.||Subsurface irrigation is most appropriate unless water is disinfected.|
|Air handling condensate||Condensed water on air handling unit surfaces that is collected and stored.||Condensed water can corrode metals because condensate can be slightly acidic. Water may absorb copper from cooling coils.|
|Purified water system discharge||Water that is discharged from water purification systems (called "concentrate").||Filtration is likely required. Highly dissolved solids can pose issues for cooling towers and landscape.|
A building that captures alternative water may require a dual plumbing system, which has two separate distribution networks to deliver potable water and alternative non-potable water to separate end uses. A building with a dual plumbing system minimizes potable water use only for applications that interface directly with occupants, such as restroom faucets and showers and kitchen equipment.
Successful Example Projects
- The U.S. Army's Fort Buchanan in San Juan, Puerto Rico, installed rainwater harvesting systems to flush toilets and urinals. The projects were implemented through an energy savings performance contract.
- The U.S. Department of Interior implemented a large-scale system that reuses foundation water for cooling tower makeup at its Washington, D.C., headquarters.
- The General Services Administration designed and constructed a building that reclaims treated wastewater at the San Ysidro Land Port of Entry in San Diego, California.
- EPA's Science and Ecosystem Support Division in Athens, Georgia implemented a project that captures condensate from air-handling units and reuses the water for cooling tower makeup.
Treat Wastewater On-site and Return to the Original Water Source
A net zero water building closes the loop on the water system by returning water to the original water source. The original water source is considered freshwater sources from same local watershed or aquifer as the building's supply water.
If the building is located within the original water source, water can be returned through an on-site septic system or wastewater treatment system, which discharges treated wastewater to the local aquifer. (Treated wastewater can also be reclaimed as an alternative water source and reused within the building as stated above.)
It is important to note that treating wastewater on-site may not be a viable solution for many buildings due to space and cost constraints. If space or cost is an issue, the building will have to depend on using alternative water to offset the use of freshwater or return water back to the original source through green infrastructure.
Successful Example Projects
The National Guard Center Camp Rilea, located in Astoria, Oregon, treats wastewater on-site and recharges groundwater through rapid infiltration basins.
Design Green Infrastructure Features to Return Water Back to the Original Water Source
Another option for returning water to the original water source is through green infrastructure (also called low-impact development). Green infrastructure uses landscape features that retain stormwater on-site and infiltrate it back to groundwater.
These features minimize water loss due to runoff and allow water infiltration through soil into the local water table. While this process preserves the natural flow of water, it also helps prevent flow on hardscape where water may be more exposed to contaminants and may more readily be lost into the atmosphere through evaporation. Green infrastructure examples include bioswales, rain gardens, and permeable pavement.
If the building is not located within the watershed or aquifer of the original water source, then returning water via green infrastructure to the original water source will be unlikely. The option for the net zero water strategy would have to depend on using alternative water to offset the use of freshwater.
Successful Example Projects
Fort Riley, Kansas, installed permeable pavement at an elementary school to pilot green infrastructure and use it as a tool for sustainability education.
Tips for Net Zero Design and Continued Operational Success
Incorporate Net Zero into Design Reviews of New Projects
When designing a net zero water building, it is important to incorporate these net zero elements early in the process. Clearly lay out the net zero water goals of the building at the onset of design. Specify net zero water equipment and elements at the initial design charrette. Bring stakeholders to the table at the beginning of the design process to ensure everyone agrees on the net zero water goals.
Develop Contract Language to Maintain the Integrity of Net Zero
Include language in the contract that ensures the net zero water elements are installed per the design. The language should specify that the equipment specifications identified in design phase will be cross-walked with the contractor's procurement to ensure that the correct equipment is purchased and installed. Add language to the contract that includes performance metrics on water use that require the building meets the water use determined in the design phase. This provision should include a requirement to meter the building's water use, major water-consuming equipment, alternative water systems, and on-site wastewater treatment systems.
Commission Buildings Water and Wastewater Systems
All contracts should include language that ensures net zero water equipment and features are commissioned during the construction phase and on completion of construction. This will ensure that the building's water systems are installed and tested to perform per the design specifications. Develop a commissioning plan that includes the overall objectives, commissioning strategies, and project team. The plan should include the tests required to commission each major water system. Tests may include flow rate monitoring to ensure that equipment meets the manufacturer's specified flow rate. This measurement can be done through a flow meter or spot flow measurement. All equipment should be tested to ensure the connections are not leaking. For alternative water and wastewater systems, it is recommended that the commissioning plan require water quality testing to confirm that the treatment system is producing the desired level of filtration and/or disinfection.
Develop a Building Operation Plan
Ensure the building operation plan includes specific operation and maintenance measures of water equipment. The plan should describe the measure, action items that should be performed, how often the actions should be performed, and the personnel responsible for each action. Action items should include checking for leaks, broken components, and loose connections. Also ensure that manufacturer-specified use and care instructions are being followed.
Meter Water Use and Monitor for Leaks and Operational Issues
Metered data provides critical information on the building's water use to ensure that the building is performing as designed. The building should be metered as a whole to monitor total water use. Water-intensive applications such as irrigation and cooling towers should be sub-metered. Alternative water systems should also be metered to monitor water production. On-site wastewater should also be metered so that the total amount of treated wastewater returned to the original water source can be monitored and measured. Water infiltration of green infrastructure features can also be monitored with flow sensors.
All meters should be advanced meters able to download data at least in hourly intervals. The interval data can be used to monitor the building and equipment for unusual spikes in water use that can pinpoint leaks or operational issue.
Implement an Active Institutional Change and Training Program
For a net zero building to succeed, occupants must be engaged in and knowledgeable about the building's net zero elements and functions. An institutional change program can be an effective way to train occupants on a building's key net zero features. Such a program integrates technology, policy, and behavior into the building's daily operations.
Example elements of such an institutional change program include training occupants to identify plumbing leaks, providing an easy way to report leaks, setting periodic goals for building water use, informing occupants on water performance through newsletter and email announcements, and giving awards for meeting water reduction targets. Learn more about institutional change.
Develop Campus Master Plan
For a net zero water campus, develop a master plan that prioritizes projects for implementation and specifies equipment that should be installed in new construction and renovations. A net zero master plan should include elements that ensure net zero water goals are systematically implemented, including items such as a prioritized list of water projects with targeted goals, an implementation timeline, and equipment specifications that are required for all new construction and renovations.
Net Zero Water Building Examples
The following two examples illustrate the concept of a net zero water building using buildings with different approaches to achieving net zero water.
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