Double Zero simply means Zero Water Ready and Zero Energy Ready
Kreger Design Build designs and builds climate-responsive buildings informed by the globally emerging Passive House Standard together with advanced water conservation strategies. Located at 6,720 ft above sea level in the semi-arid mountain and mesa lands with views of two mountain ranges, weather extremes and water challenges inspired the owners and design team to prove "Double Zero CAN be done". In the context of winter temperature extremes occasionally dropping below zero for days and of historic precipitation averages receding into the New Norm of increasingly diminished annual rainfall (Climate Change), Double Zero seemed a logical choice.
Defining and validating these innovative practices requires a third-party verification to lift them from assertions to practical solutions. In this case the design team chose:
Zero Water in this case means rooftop collection and storage of rainwater using RainVessels (as well as reuse of grey water) for up to 100% of interior water demands including potable and non-potable needs.
Potential zero water validation comes from an innovative third-party verification water modeling software that generates a Water Efficiency Rating Score, or WERS.
Developed by the Green Builder Coalition, in cooperation with Build Green New Mexico, Santa Fe Area Home Builders Association, and members of the City of Santa Fe Water Conservation Committee, it uses measurable parameters, along with a scoring scale of 100 down to 0, with zero being the most desirable. WERS' primary criteria focuses on reducing potable water demand in:
- indoor water uses by employing conservation strategies
- outdoor water conservation strategies including the EPA WaterSense program.
Zero Energy in this case refers to a zero energy building (ZEB), using advanced energy conservation design and construction strategies, substantial energy demand reductions can drive this home's HERS Rating to Zero Energy Ready, Near Zero Energy or Zero Energy. HERS also uses a scoring scale of 100 down to 0 with zero being the most desirable. In general, Zero Energy is an efficient, grid-connected solution using energy primarily from renewable sources to compensate for its own energy demand.
This first Double Zero Home's Zero Energy target is currently in process towards third-party verification to become a Passive House certified under the PHIUS+ 2015 program which was developed by the Passive House Institute US. A certified Passive House provides not only extremely low energy demand but also superior comfort, indoor air quality, durability and resilience against oncoming climate change.
The PHIUS+ 2015 certification also includes other national third-party programs:
- the DOE Zero Energy Ready Home program
- the EPA ENERGY STAR (Version 3) program
- the EPA ENERGY STAR Indoor airPLUS program.
Zero Energy Ready means future-proofing this home to easily become a net-zero-source energy home by 2030 in conformance with the Architecture 2030 Challenge.
Of course there are no Zero Water Ready and Zero Energy Ready people, just buildings.
Users' habits and choices greatly influence the Double Zero outcome.
Despite sharing the name "Zero Net Energy", several connotations define ZNB's in practice:
- Zero Net SITE Energy use:
A "Zero Net Site Energy" building means the amount of energy provided by on-site renewable energy sources is equal to the amount of energy used by the building.
- Zero Net SOURCE Energy use:
This ZNB generates the same amount of energy as is used, including the energy used to transport energy to the building from external sources (i.e.power plants). It accounts for losses during electricity transmission and it must generate more electricity than zero net site energy buildings. PHIUS identifies a national average ratio of 3.16 more source energy than site energy.
- Net Zero Energy EMISSIONS:
Also known as a zero carbon building or zero emissions building ZEB, under this definition the carbon emissions generated from on-site or off-site non-renewable fuels use are balanced by the amount of on-site renewable energy production. Other definitions include not only the carbon emissions generated by the building in use, but also those generated in the construction of the building and the embodied energy of the structure.
- Net Zero COST:
In this metric, the cost of purchasing energy is balanced by income from sales of electricity to the grid of electricity generated on-site. Such a status depends on how a utility credits net electricity generation and the utility rate structure the building uses.
PHIUS lists both SITE and SOURCE energy use as important energy metrics to define performance.