The ups and downs of life cycle thinking – Part Two
July 2016

Previously on the CAB Channel…I outlined how aluminium is making a significant contribution to sustainable cities, and in particular I highlighted the compelling case study evidence presented in the International Aluminium Institute (IAI) funded “Towards Sustainable Cities” series of publications.

The third report in the series, “Aluminium and Life Cycle Thinking”, was published in 2015 and it focuses on the use of Life Cycle Assessment (LCA) techniques to quantify a product’s environmental impact during its lifetime, from its manufacture and use through to its deconstruction, reuse and recycling at the end of life.

While LCA offers a rigorous, quantitative means to assess the environmental impact of a product and as a technique it has been in use for over twenty years, its application in the building sector is relatively immature. Complex assemblies such as curtain walling, windows and doors are only just beginning to be understood and modelled using LCA practices. LCA is itself a complex science, with its own terminology, complex datasets and methodological snares. However, it is becoming increasingly important, with Environmental Product Declarations and building sustainability assessment schemes such as BREEAM turning to LCA as their basis.

Inevitably, the comparability question arises: “OK, so can I use LCA data to compare products?” It is here that the report authors refer to the use of “nuanced” LCA, described as a design tool that can allow for a particular comparison of different material assemblies that serve the same function in the building, while respecting each option’s unique material attributes and design logic. So the answer to the question is: “It depends…” Or at least, a red flag is raised that product comparisons must be handled with care, with attention drawn to the end of life stage.

LCA modelling practice is not fixed and it should allow for fine-tuning to explore the complex relationships between material selection, manufacturing processes, durability and recycling rates, to name but a few. In particular, the report highlights the significance of the end of life stage, which is important for materials that may require a relatively large amount of energy for initial production but that have the potential to save resources through their use, reuse and recycling at end of life. LCA should be used to model the total environmental cost of ownership.

Chapter Three of the report sets out an LCA for window framing, looking at aluminium, timber, aluminium-clad timber and PVCu materials, noting that window frames represent under-studied, complex assemblies that contribute both to the embodied environmental impacts of building components and moreover to their energy performance. It also notes that few studies to date have adequately examined use-stage impacts or considered the effects of window frame repair, replacement, recycling or disposal.

How recyclability and recycling, durability and manufacturing are modelled all have a significant impact on the LCA results, which will be explored in the third and final article in this series.