Achieving Net Zero Water

In recent years, we’ve discussed the move toward net zero energy in many of the stories and projects we have featured. As the interest in achieving net zero energy increases, so does the interest in achieving a more sustainable future in other areas as well, such as net zero water.

A look at how two projects have achieved net zero water as part of the Living Building Challenge

By Marcy Marro

The Regenerative Porch on The Kendeda Building for Innovative Sustainable Design. (Photo: Jonathan Hillyer, courtesy of The Miller Hull Partnership LLP)

The goal of net zero water is to have a building fully responsible for generating all of its potable water needs and treating all discharge waste. By creating a self-sufficient water resource, all water is either harvested on-site or sourced from a closed-loop system, while waste water is treated and reused or infiltrated within the property.

The Living Building Challenge looks to create positive environmental impacts through seven performance categories, or petals. Each petal is divided into imperatives, for a total of 20 imperatives, which can be applied to almost any building of any size in any location, new or existing. The seven petals are place, water, energy, health + happiness, materials, equity and beauty.

Following are two examples of projects—one, a single-family residence in the Seattle area, and the other, a larger university building in the southeastern United States—that have achieved net zero water as part of the Living Building Challenge.

Photo courtesy of McLennan Design.

Heron Hall, Bainbridge Island, Wash.

When the founder of the Living Building Challenge, Jason F. McLennan was designing a home for his family, he wanted a home that would last a few centuries. A designer and urban planner, McLennan is the founder of McLennan Design in Bainbridge Island, Wash., the firm that worked on his home, Heron Hall. Sitting on 1 acre of land along a man-made estuary, the 3,300-square-foot house is designed for net zero water and energy to meet Living Building Challenge requirements.

Despite living in a region known for rain, Bainbridge Island typically has more than 30 days of drought each summer and a lower rainfall count than most of the eastern and southern cities in the U.S., McLennan had to be creative in how he achieved his goal of living completely off the water grid and live on rainwater alone for his year-round water needs. To do so, McLennan’s first step was to dramatically change the amount of water required within the household by turning off faucets while not actively using water, and selecting and installing the most water-efficient appliances and fixtures available on the market including composting toilets. By replacing a standard flush toilet with Phoenix’s foam flush composting toilet system by Advanced Composting Systems LLC, Whitefish, Mont., he is using approximately 2 to 4% of the water an average person uses throughout the day to flush. Additionally, landscaping at Heron Hall consists of native or naturalized plantings that require very little irrigation once established.

McLennan’s next step was to design the water systems for Heron Hall based on a comprehensive understanding of the Pacific Northwest’s climate, where rain tends to fall from October through June, with July, August and September being generally dry without any major precipitation. With this information, he worked closely with 2020 Engineering, Bellingham, Wash., and RainBank Rainwater Systems, Snohomish, Wash., to develop a water plan.

The house features a 22-gauge structural standing seam roof from Metal Sales Manufacturing Corp., Louisville, Ky. The roof is the main collector for the rainwater collection system that provides 100% of the family’s water. To be usable, the water shedding from the roof needs to be clean through a three-step process. McLennan specified Fluropon Pure metal coating from Minneapolis-based Sherwin-Williams Coil Coatings, which is the first metal roof coating on the DECLARE list of products under the Living Building Challenge. Water running off the roof is then collected into a 15,000-gallon steel water tank cistern from Contain Water Systems, Marble Falls, Texas, before it is moved into a stair tower where it is treated by UV and carbon filters before going into a small buffer tank where it can be used daily. The zero-impact water system has no fluoride, chlorine, residual drugs or contaminants. Water that is collected from the south slope of the roof is directed to a 9,000-gallon agricultural cistern for landscaping and on-site agriculture.

After the 12-month occupancy period per the Living Building Challenge, it was confirmed that the McLennan family uses an average of 13 gallons of water per day, an 87% reduction from the average American.

Diagrams courtesy of The Miller Hull Partnership.

The Kendeda Building for Innovative Sustainable Design, Atlanta

Designed by The Miller Hull Partnership LLP of Seattle, in collaboration with Atlanta-based Lord Aeck Sargent, a Katerra company, the 37,000-square-foot Kendeda Building for Innovative Sustainable Design is a partnership between the Georgia Institute of Technology and The Kendeda Fund to build the most environmentally advanced education and research building in the southeast United States. The LEED Platinum building is pursuing net zero water as part of the full Living Building Challenge Certification.

Biohabitats, Baltimore, designed to meet the project’s Water Petal and net-positive water goals by performing water-balance modeling and developing and directing the strategy for water harvesting, sizing, and treatment and reuse approaches. This included rainwater harvesting, grey water treatment, composting toilets, and condensate reuse and irrigation. While grey water is treated through constructed wetlands and a recharge system, condensate and rainwater reuse systems provide 100% of the water for the green roof and site irrigation.

Rainwater is harvested from the roof canopy, which has gutters that collect all of the rainwater that falls on the photovoltaic panels and brings it to a 50,000-gallon cistern in the basement, where it is filtered to meet the building’s potable needs. According to Biohabitats, The Kendeda Building has the first rainwater-to-potable water system approved in Georgia for a non-single-family residence.

As Miller Hull’s Living Building Challenge Services Director Chris Hellstern explains, The Kendeda Building’s rainwater harvesting system is designed to be an integrated part of the building that works with several design features at once. “Using the large PV canopy that provides all of the building’s net-positive energy generation, rain is collected from those panels in a uniquely designed system to capture the water off each row of panels. From here, everything flows down into the building’s 50,000-gallon, cast-in-place concrete cistern. At this point, it is an on-demand system and the rainwater can be pulled to each plumbing fixture as needed. Just prior, the rain passes through a treatment skid in the basement that has been left exposed for educational value. A series of micron filters and UV treatment ensure the water is safe for drinking.”

Additionally, Hellstern explains that the grey water is treated on-site through a series of filters and landscaping that lines the Regenerative Porch–an outdoor gathering and classroom space shaded by the PV canopy. It is designed to utilize cooling breezes just as the historic vernacular of Georgian home porches have done for years. “Treated grey water is then infiltrated subsurface,” he adds. “Blackwater is handled through composting toilets. With almost a year of operation–including COVID-19-related shutdown time–the building is performing as net-positive water. The Kendeda Building’s operator describes the building as ‘sipping water.’”

Working together, these regenerative design responses help The Kendeda Building achieve the Living Building Challenge Water Petal and operate as net-positive water. “This project will be the first to achieve full Living Building Challenge Certification status in the southeast United States where there are greater climate challenges like extreme heat and humidity and heavy thunderstorms,” Hellstern adds.