Building life cycle assessment is a methodology used to measure the environmental impact and energy consumption of a building throughout its entire lifespan, typically across 50 years.

The whole use of the building is taken into account for a more realistic portrayal of overall environmental impact, shifting focus away from only looking at carbon emissions produced during the material manufacturing phase.

Conducting building life cycle assessments allows us to identify which phases of the build are energy efficient or inefficient, which areas could show improvement, and a study of different construction systems to see which materials perform better or worse at various points of the build lifespan.

By analysing energy use across the lifespan of a building we are able to select more environmentally responsible and sustainable construction solutions which result in a reduction of carbon emissions in New Zealand’s building industry.

Four Phases

Building life cycle assessments are measured across four phases. Firstly production, which encompasses raw material extraction and product manufacturing. The second phase is construction, which includes transportation of materials and equipment to the site as well as the build. The use phase, which comes after, is where the highest energy usage is measured. This is the longest phase and most energy intensive as it includes consistent operational use across decades, maintenance, repairs and refurbishments.

The final phase is end-of-life which involves demolition of the building when it is no longer fit for use, recycling and disposing of materials, as well as transportation in removal of materials. Energy use across each of these phases is studied in a building life cycle assessment, resulting in an accurate collection of data that shows the environmental impact the building will have over the decades of its existence.

Material Performance

Comparative studies highlight strengths and weaknesses of construction materials we are currently using. Some materials perform better than others during specific phases, and some materials show an overall better performance across the entire life cycle assessment. Comparing timber frame homes with insulated concrete formwork indicates differences across various phases. ICF shows to have higher energy use during the production phase when compared with timber. On the other hand, when isolating the longest phase, the use phase, ICF has significantly lower energy consumption compared to timber.

Overall, this makes ICF the more favourable option when considering the entire life cycle assessment as it produces less carbon emissions across the entire lifespan. Due to the structural toughness and airtight design, which offers good thermal efficiency because of the high level of insulation, ICF is able to accomplish these notable energy usage reductions during the use phase.

Timber performs well in the production phase, but underperforms during the operational phase. Air leakage and heat loss through thermal bridging is a prominent issue in timber construction. The build is thermally inefficient and requires much more energy to adequately heat and cool the building.

Environmental Impact

As Nz Continues to take steps towards being environmentally conscious and reducing our carbon footprint, case studies into carbon emissions from the construction industry are important to analyse. A building life cycle assessment provides a comprehensive and structured look into environmental impact across phases.

For several construction materials there are trade-offs, where some perform better in particular phases than others. As a whole, it is beneficial to be looking at the bigger picture and consider the entire lifespan of a building in order to proceed with more sustainable construction solutions and develop better building practices.

Anthony Corin and his team specialise in property development and construction using ICFs and operating through a relational contract, open-book system. Shorcom Ltd, 0800 SHORCOM, www.shorcom.co.nz