Net Zero Water

Giving Green Fondation (GGF) provides information about net zero water and provides strategies on how to design and implement net zero water buildings.

By following net zero water strategies, GGF can construct buildings and campuses that preserve natural water resources, help improve water infrastructure, and secure water to meet mission-critical needs.

What Is a Net Zero Water Building?
A net zero water building (constructed or renovated) is designed to:

  • Minimize total water consumption
  • Maximize alternative water sources
  • Minimize wastewater discharge from the building and return water to the original water source.

Net zero water creates a water-neutral building where the amount of alternative water used and water returned to the original water source is equal to the building’s total water consumption.

The goal of net zero water is to preserve the quantity and quality of natural water resources with minimal deterioration, depletion, and rerouting of water by utilizing potential alternative water sources and water efficiency measures to minimize the use of supplied freshwater. This principle can be expanded to the campus level.

Measuring Net Zero Water

Understanding how net zero water can be measured is important so that you can determine if your building has met the net zero objective. Net zero water can be represented by a simple formula where:

  • Total water use is the amount of water consumed within the boundaries of a building from all sources (potable and non-potable including freshwater and alternative water) over the course of a year.
  • Alternative water use is the amount of water consumed within the boundaries of a building from sustainable water sources not derived from freshwater sources over the course of a year. In a net zero building, the total annual water use should be offset by alternative water in part or completely.
  • Water returned is the amount of water collected from the building systems (green infrastructure and on-site treated wastewater) and is returned back to the original water source over the course of a year. In a net zero building, the total annual water use should be offset by water returned to the original source in part or completely.

To verify that the building is operating at net zero, collect annual water use data for each water flow:

  • Potable water use
  • Non-potable water use (from freshwater sources)
  • Alternative water use
  • Treated wastewater on-site returned to original water source
  • Stormwater infiltrated to the original water source through green infrastructure.

Sum all freshwater use and alternative water use to calculate the building’s total annual water use. Next, sum alternative water use and treated wastewater and stormwater returned to the original source. If this sum is equal to or greater than the total annual water use, then the building is considered net zero water.

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.

Scenario 1: The Ideal Net Zero Water Building

An ideal net zero water building uses on-site alternative water sources to supply all of the building’s water needs. All wastewater discharged from the building is treated on-site and returned to the original water source.

Scenario 2: The Mainstream Net Zero Water Building

A more main stream net zero water scenario is shown below. This building offsets freshwater with alternative water and recharges water back to the original water source through green infrastructure.

All the graphic shows incoming and outgoing water flows of the building.

  • Potable water is supplied and treated on-site from harvested rainwater.
  • Alternative non-potable water is supplied and treated on-site from harvested stormwater and graywater, which is lightly contaminated wastewater generated by lavatory faucets and showers.
  • Wastewater is treated on-site and returned to the local aquifer.
  • Stormwater is recharged to the aquifer through on-site green infrastructure features on the building’s landscape.