What makes New Zealand houses expensive: A detailed construction cost analysis of an energy-efficient house.

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Abstract
The escalating global primary energy demand highlights the need for sustainable practices, particularly in the New Zealand residential sector. Despite the proven benefits of well-designed, energy-efficient houses in reducing energy consumption and ecological footprints, misconceptions about high construction and operating costs hinder their wide adoption. Therefore, this study presents a detailed cost breakdown of an energy-efficient house in New Zealand, providing insights into cost distribution and offering a systematic approach to cost planning for future projects. A case study approach was employed, analysing an energy-efficient house with an estimated Homestar rating of 7-8 and a Gross Floor Area of 121 m². Data were obtained through document analysis, including drawings, specifications, quotations, manuals, and other building documents. A cost comparison was conducted based on the elemental breakdown provided by the New Zealand Institute of Quantity Surveyors and cost data from QV Costbuilder. Findings indicate that the total construction cost of the energy-efficient house, approximately NZD 3,700 per m², exceeds the average cost of similar single-storey houses in different New Zealand cities. According to the cost distribution analysis, the main contractor accounted for 68% of the total costs, with materials comprising 44%, labour at 16%, and management costs at 8%. Based on elemental analysis, internal finishing, external fabric, and building structure contributed 29%, 24%, and 19%, respectively. The study is limited by procurement type, building shape, and site-specific conditions. However, its findings provide valuable insights to inform decision-making and enhance the feasibility of energy-efficient houses in New Zealand.

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