Last month we alerted you to the newly-released first draft of Green Star Buildings for New Zealand. Due to replace the current Green Star Design & As Built certification from mid-2025, Green Star Buildings NZ sets a new benchmark for sustainable commercial buildings.
As part of the draft proposal, grey water recycling and rainwater harvesting could well provide strong opportunities to lift the Green Star points you can achieve under the Green Star Water Use Calculator. In turn, this means that installing Hydraloop, the world’s first on-lot water recycling system, to recycle grey water in your property, could give your project or property the boost it needs to lift its rating under the new system.
GreenStar quantifies the building’s water usage using the “Green Star Water Use Calculator” and assesses its achievement level using a comparison method, described in their Criteria as a “Reference Building”.
There are no specifics on a “reference building”; our understanding is it is a similar commercial building used for the same purpose and of a similar scale – this is at the discretion of the NZGBC and Green Star.
The “reference building” method is similarly used for the Energy Use, Upfront Carbon Emissions, and Life Cycle Impacts criteria.
GreenStar quantifies the building’s water usage using the “Green Star Water Use Calculator” and assesses its achievement level using a comparison method, described in their Criteria as a “Reference Building”. There are no specifics on a “reference building”; our understanding is it is a similar commercial building used for the same purpose and of a similar scale – this is at the discretion of the NZGBC and Green Star.
The “reference building” method is similarly used for the Energy Use, Upfront Carbon Emissions, and Life Cycle Impacts criteria.
The table below is a summary of the points available under the proposed GreenStar standard.
Green Star Water Use Calculator
Within the calculator, there is room to include water reduction incurred by rainwater harvesting and grey water recycling – one of WaterSmart’s specialties. Additionally, there is also a Sewerage calculation component of the calculator. Buildings can claim an innovation point for a 90% or more significant reduction in flow to the sewer.
The calculator allows you to account for up to 100% of the project’s non-potable water demand met by rainwater, greywater, or a combination.
The standard consumer of non-potable water in a commercial setting is likely to be toilets unless it is a building that incorporates any commercial washing machines. The other potential uses are irrigation systems.
A combination system would allow the building’s primary water supply to be recycled greywater and a secondary top-up feed from collected rainwater. This combination of systems is an area that WaterSmart specialises in. Theoretically, combining rainwater harvesting with an industry-leading product such as Hydraloop could yield upwards of a 45% potable water reduction in a building – Solely Achieving “Credit Achievement” and 2 points.
Secondly, solely incorporating Hydraloop to facilitate grey water recycling could yield around a 20-30% in potable water use.
If a rainwater harvesting system is specifically designed to the project’s/building’s size (another of WaterSmart’s specialties), then all non-potable fittings could be serviced by rainwater, yielding up to a 45% reduction in potable water use.
Furthermore, if you were to incorporate a to-scale water treatment system for rainwater, it is a feasible that up to 100% of both potable and non-potable water requirements could be serviced by rainwater – certainly reaching Exceptional Performance (3 points).
Combine any of these options with water-efficient fixtures, and the building could be well on its way to the “Exceptional Performance” Criteria.
Within the calculator, you input your ‘Water Consumption due to Fittings’, using water efficiency (e.g. L/min), whether they are supplied by rainwater/greywater (Yes/no), and no. of fittings.
Further on in the calculator, you are required to validate your claims for Rainwater and Greywater. Achievement is at the discretion of the Green Star assessor, but WaterSmart can assist with the calculation proof necessary for validation.
Product Specifications
In combination with the calculator, the guidelines require:
- Manufacturer’s information, including backwash volume and frequency of filter cleaning.
- Drawings and specifications for infrastructure.
Regarding our rainwater harvesting products, Aquacomb and FenceTank, they have achieved third-party eco-label certifications meaning they are eligible for Green Star points under the sustainable materials section.
Case Studies
WaterSmart has consulted on numerous projects where Hydraloop, combined with rainwater harvesting, has been necessary to get the commercial project past the planning stage. Projects have ranged from apartment buildings to retirement villages and Maraes. WaterSmart has the building blocks ready to incorporate Hydraloop (grey water recycling) and rainwater harvesting in your next Green Star project.
Additionally, also review the case studies on NZGBC’s website: https://www.nzgbc.org.nz/greenstar/green-star-case-studies
