Otara project: Thermal performance analysis of Fibre Reinforced Earth Composite Indigenous Housing in Auckland - NZ

Unlike timber framed structures, which is the construction of most residential dwellings in New Zealand, earth buildings passively moderating more extreme seasonal temperature fluctuations by maintaining warm indoor temperatures in winter and keeping cool in the summer, due to the thermal mass of the thick rammed earth walls. In temperate climates like Auckland, this works well. The thermal mass of the rammed earth walls causes the indoor air temperature of earth buildings to follow the daily variation of the outdoor air temperature with significant attenuation and time lag, creating a thermally stable indoor environment. This paper discusses the thermal performance of the UKU harakeke soil-cement houses, based in two locations in south Auckland. The projects are two indigenous Maori dwellings, that have been developed with a high level of consultation throughout the local community. The materials (earth as a building material - and New Zealand Flax (harakeke) have been historically valued by Maori groups for their cultural and practical significance. The project has involved research in the literature on the existing understanding of harakeke and earth use as reported in the Traditional knowledge and Practices with Fibre extraction (1). Monitored data (temperature & humidity) were collected on both sites and compared with simulated results (Visual Doe 3.1 - LBL/ TAS - EDSL, UK) for validation purposes. The simulation runs (using different values for wall thickness) aimed at evaluating the thermal performance of the fibre reinforced earth composite for minimum values of thermal mass. This paper reports on the initial results for summer monitored and simulated data. The final results of this study will inform further studies into earthquake building resistance, so these could be cross-evaluated into practical and economical applications of low income housing solutions.