Abstract
In New Zealand, housing is typically low density, with light timber framing being the dominant form of construction with more than 90% of the market. From 2020, as a result of the global pandemic, there was a shortage of timber in New Zealand, resulting in increased popularity for light steel framing, the main alternative to timber for housing. At the same time, the New Zealand government is committed to sustainability practises through legislation and frameworks, such as the reduction of whole-of-life carbon emissions for the building industry. New Zealand recently announced reducing its net greenhouse gas emissions by 50% within 2030. Life cycle assessment (LCA) is a technique for assessing the environmental aspects associated with a product over its life cycle. Despite the popularity of LCA in the construction industry of New Zealand, prior research results seem varied. There is no unified NZ context database to perform an LCA for buildings. Therefore, in this paper, a comprehensive study using LCA was conducted to quantify and compare the quantity of carbon emissions from two commonly designed houses in the Auckland region, one built from light timber and the other from light steel, both designed for a lifespan of 90 years. The cradle-to-cradle system boundary was used for the LCA. From the results of this study, it was found that the light steel house had 12.3% more carbon in total (including embodied and operational carbons) when compared to the light timber house, of which the manufacturing of two houses had a difference of 50.4% in terms of carbon emissions. However, when the end-of-life (EOL) analysis was included, it was found that the extra carbon could be offset due to the steel’s recyclability, reducing the amount of embodied carbon in the manufacturing process. Therefore, there was no significant difference in carbon emissions between the light steel and the light timber building, with the difference being only 12.3%.
Highlights
As the population increases globally, the demand for housing will naturally increase [1]
The Life cycle assessment (LCA) results confirmed that the light timber house emitted 13.72 kg CO2 eq/m2/year, while the light steel house emitted 15.41 kg CO2 eq/m2/year of total carbon
There was no significant difference in carbon emissions between those two houses, considering the carbon offset from the building materials after their EOL stages
Summary
As the population increases globally, the demand for housing will naturally increase [1]. In New Zealand, the building and construction sector contributes 20% of the nation’s total carbon emissions [6]. CFS members can be rolled into different cross-sectional shapes and optimizing these shapes can further improve their load-bearing capacities, resulting in a more economical and efficient building solution. These CFS members (especially channels) are often used in beams [20,21,22,23], columns [24,25,26,27,28,29,30,31,32], shear walls [33], and cladding systems [34]. It is essential to consider the energy performance of the CFS structures
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