Water Performance Benchmarks for New Zealand: Understanding Water Consumption in Commercial Office Buildings

Abstract

There is an increasing amount of literature outlining the issues underlying water shortages and restrictions to come in most regions of New Zealand. The problem is not helped by rising demands and climatic changes, as well as both a lack of measured data, and a lack of any demand-side incentives. No attempt has been made to assess how the users of commercial buildings are consuming potable water. There are no benchmarks for water performance in buildings, hindering attempts to improve water efficiency.

This study investigated the water use in 93 Auckland and Wellington commercial office buildings. The data collected from both survey level water audits (on-site investigations, historic billing analysis) and full water audits (water monitoring), were used to develop market-based water performance benchmarks, and a Water Efficiency Rating Tool (WERT). This was done to understand water consumption in these buildings, and to determine the feasibility of using performance based data for the development of a water benchmarking system.

The principal results were in the form of both a benchmarking index system, and the WERT. The benchmarking study found that Net Lettable Area (NLA) was the most statistically and pragmatically appropriate driver for water use. lt also found that, due to the distinct difference in tariff structures and incentives between Auckland and Wellington, different benchmarks for the two regions (Auckland 'Typical' use 0.76m³ / m² / year, and Wellington 'Typical' use 1.03m³ / m² / year) were required.

The WERT calculates a building Water Use Index (WUI- m³ / m² / year) , estimates its end-use disaggregation, and provides recommendations through outlining the financial viability of implementing specific water efficiency measures. This tool utilised six design criteria to ensure target market usability: accuracy (demonstrated at ±8. 5%) ; relevance and realism; practicality; promotion of understanding and action; objectivity; and effective communication.

Further recommendations included satisfying some of the many knowledge gaps present in the New Zealand water industry concerning office building water use. These included: introducing a national legislative or standard document providing guidelines on demand-side management of water; investigation into changing tariff structures to include a volumetric charge for all building types to increase individual awareness and education of water use; research into the durability of water meters; and expanding the research to include other New Zealand regions.