Environmental life cycle assessment of analogous New Zealand 'exemplar house' designs

Abstract

To reduce the environmental impact of residential construction a holistic understanding of the building life cycle is necessary. Life Cycle Assessment (LCA) is well suited to the task of calculating the impacts associated with building products and systems so it is used in this study to assess building material options for a typical New Zealand house design. The LCA and underlying data adhered to international standards and framework. Four house designs comparing concrete and timber flooring, steel and timber framing and fibre cement and timber cladding were investigated. The different designs were modified to have the same thermal performance using NZS4214:2006. Consequently the difference in environmental performance can be attributed to the wooden building products. Substituting steel with timber framing results in a 20-30% decrease in global warming emissions, eutrophication and photochemical oxidation, but an increase in land and water use. Exchanging concrete with timber flooring results in a similar trend but there is a significant reduction of solid waste. Substituting fibre cement cladding with timber weatherboards yielded had little difference on the LCA-metrics. It is an over-simplification to focus on environmental performance as other building product characteristics are important.