Sustainability in Prefabricated Architecture: A Comparative Life Cycle Analysis of Container Architecture for Residential Structures

Abstract

The aim of this research is to establish whether container architecture in the residential sector of New Zealand is energy efficient in contrast with traditional houses built by different building materials. This study is part of a discussion on sustainability in prefabricated architecture. The term "container architecture" has not been assessed in depth yet. On the other hand, the concept of prefabrication in architecture is well documented. Despite the large amount of empirical knowledge, little is known about container architecture in the residential sector. A comparative life cycle analysis has been undertaken by emphasising three different approaches: Energy consumption, CO2 emissions and the thermal performance of three conventional building materials (steel, concrete and timber-based structures) in the residential sector of New Zealand. Results from international studies of the Life Cycle Analysis (LCA) method in houses have been mixed. A number of studies suggest the importance of this methodology in order to achieve benefits in the reduction of energy consumption and CO2 emissions. Most of these studies agree that operational energy is the highest driver of both the energy consumed and CO2 emitted. However, some studies disagree with this approach due to the assumption made in the underestimation of the energy used in the transport of raw materials in the construction process of a building. Establishing a comparative life cycle analysis between a container-house, a concrete dwelling and a timber residence may provide further insight in the understanding of the patterns related to the energy consumption and CO2 emissions in the residential sector when container houses are used. Such understanding may be useful in developing more efficient houses. The household data for each project has been calculated and this information has been used to explore the drivers of the energy consumption and CO2 emissions through the lifespan of every example. Three case studies have been selected for this comparative life cycle analysis. Selection criteria are based upon relationships between container-architecture's main features that match with some ideals of the Modern Movement in Architecture: the construction of prefabricated and mass produced elements, modularity and formal simplicity. Emphasis is put on numerical relationships related to shipping steel-boxes, size and form, scale, material properties, density, site location and climatic conditions. The three case studies are: for steel, the Stevens House, which is the first container house constructed in Wellington, for concrete, a single dwelling unit of the Jellicoe Towers, a post-WWII model of Modern Architecture in New Zealand built in the late 1960s and for timber, the Firth House, a wooden-based house designed by Cedric Firth which was inspired by the works of Walter Gropius and Konrad Wachsmann, German figures of the Modern Movement in Architecture. The life cycle energy consumption is given by using two different software packages. The first is known as Gabi, which has a European database. It is useful to calculate the total amount of energy used and the amount of CO2 released into the atmosphere by the different projects through their lifespan. The second program is New Zealand software known as ALF 3 (Annual Loss Factor 3), developed under BRANZ (Building Research Association of New Zealand) which is useful to calculate space heating energy. The outcome of the research shows that the usage of shipping containers in buildings leads to a major consumption of energy (per square metre) and release of CO2 into the atmosphere (per square metre) in comparison with traditional concrete and timber buildings.