Creating developments that operate within the water balance of a given place and climate
“The intent of the Water Petal is to realign how people use water and to redefine ‘waste’ in the built environment so that water is respected as a precious resource.” International Living Future Institute
The Water Petal has only one imperative, Net Positive Water, which requires one hundred percent of occupant water to come from captured precipitation or closed loop water systems. Water used on site for drinking or irrigation must also be treated on site, without the use of chemicals if allowed by the regulatory authority. This helps ensure that certified projects are able to operate sustainably within the water balance of a given place and climate.
For a Living Building in Atlanta, Georgia, an integrated approach is needed for onsite capture of the variable amount of available water and to optimize it for the building’s needs.
- Atlanta has received an average 50 inches of rainfall annually between 1981 and 2010 - an amount that is equal to Seattle, Washington. However, recent prolonged droughts and rising sewer bills have made water a regionally critical issue.
- In addition, Atlanta has very limited available groundwater and relies on rivers, streams and reservoirs for its municipal water supply. The City is relatively close to the headwaters of these rivers and streams, which limits the ability to withdraw water sustainability.
Achieving Net Positive Water
The Kendeda Building relies upon rainwater, greywater, and stormwater systems to achieve the Net Positive Water requirement. Collectively, these systems will supply all the potable water demands for the building while recycling waste water and stormwater to recharge the surrounding aquifer.
Rainwater: Converting Rainwater to Drinking Water
The Kendeda Building will have the first rainwater to potable (i.e. drinkable) water approved system in Georgia for a non-single family residence. This system is permitted as a Public Water Supply System through Georgia’s Environmental Protection Division.
Rainwater will be harvested from the 913 panel photovoltaic (PV) array, roof deck, and green roof to supply all potable water demands for the building. After the water is collected, it will be filtered and routed to the 50,000 gallon cistern in the building’s basement for holding. The cistern system treats approximately 41 percent of the annual rooftop runoff collected; the remaining 59 percent of the annual rooftop runoff will be released from the cistern and directed to onsite stormwater systems.
- The design team determined that a 50,000 gallon cistern would provide ample capacity to overcome drought and provide water resiliency after studying 31 years of drought and precipitation data and stress testing the model for varying occupancy and water use patterns (high, moderate, low).
- While the building is allowed one initial fill before the building is occupied; the cistern will begin to collect water as soon as the roof, piping, and filtering is in place to help eliminate the need for an initial fill with city water.
- The building will maintain connections to city water and sewer from a regulatory and life safety perspective.
- Over the course of a year, at least 74,550 gallons of excess rainwater from rooftop harvesting will be used to offset the water drawn from district/campus cooling systems. This water will be used in the building for radiant heating and cooling systems as well as the HVAC system.
As water is needed, it will be pumped from the cistern to a filtering tank and disinfected with UV lighting to potable standards, then piped throughout the building for potable water needs. Potable water uses in the building include sinks, water fountains, showers, and the minimal amount needed for the composting toilets.
- Ultraviolet disinfection (UV) is allowed by the Living Building Challenge. It should be noted, however, that UV disinfection lamps typically contain mercury, an item that requires the use of an “Exception” to comply with the Materials Red List.
Greywater: Managing Waste Water to Recharge the Landscape
Greywater (or water that does not contain organic matter) will be collected from shower drains, sink drains, and water fountains and directed to a primary tank for infiltration on site. This recycled water will be pumped to a constructed wetlands at the south end of the site, gravity fed to other filtration and disinfection tanks, and ultimately allowed to infiltrate back into the soil via leach fields at the north end of the site to recharge the surrounding groundwater.
Constructed wetlands are treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.
In addition, condensate collected from HVAC system will be used for irrigation on the green roof above the auditorium and for the drip irrigation system throughout the site.
A blackwater (water with organic matter) system will not be present on the project. Rather a total of 12 composting toilets and four urinals will be installed throughout the building to separate liquids and convert solids into a fertilizing soil which can be used for uptake by plants.
Living Buildings are only allowed to have minimal stormwater runoff. For The Kendeda Building, this is water from rainstorms not captured for potable water needs. All stormwater will be captured on site and infiltrated back into the soil though controlled design measures that leverage the site’s hydrology – namely seepage areas, rain gardens, and permeable pavers.
Kendeda Building is located on a previously developed site (formerly a parking lot). The overall design intent is to restore the site as it existed prior to pre-human development by mimicking the hydrological flow of the area and re-introducing vegetation and biology native to the region, referencing the Piedmont Forest ecosystem.
In addition to providing access to the Eco-Commons, the cascading porch areas support substantial volume storage of stormwater underneath permeable pavers. The method used for The Kendeda Building manages rainwater in dispersed locations along a sloped site. This requires careful use of gravity as a tool for equalizing a dynamic system.