The local sourcing of construction materials has taken on greater importance for clients and architects looking to achieve building projects that can be considered sustainable. It can be likened to the increased awareness of where our food comes from, and how we might be more resistant to buying out-of-season fruit in the supermarket because it has been transported halfway round the world.
Of course, construction materials generally don’t have seasons like fresh produce does. Nor do a lot of materials have the country of origin printed on their labels like fruit and vegetables. This makes the topic of local sourcing in construction a much more complex one.
Before global supply chains and transportation, people had no choice but to build using the materials available to them locally. Plenty of evidence of that remains today, especially in areas whose visual character is defined by certain masonry or roofing materials. In those cases, the material was extracted, processed, and sold all within a matter of miles.
Today, the picture is considerably more complicated.
Look at the results of life cycle assessment (LCA) for a product or material, such as in the form of an environmental product declaration (EPD), and transport is mentioned multiple times. In the early stages of the product’s life cycle, the transporting of raw materials for processing/manufacture is separate from the transporting of a finished product to site.
How are you defining ‘local’ in terms of your project? Is it feasible to specify components where the raw material is extracted, and the product is manufactured within a few miles of the site? Do you simply want to be able to say that all products were purchased from a local merchant or supplier, regardless of where the raw materials came from?
While it’s easy to see how the former is likely to have a lower overall impact than the latter in terms of transport, there is not necessarily a right or wrong answer.
The information provided in EPDs is often based on assumed travel distances, which will be more applicable to some projects and sites than others. Unless you know exactly where something is coming from, calculating accurate impact figures is very difficult.
The method of transport and the efficiency with which something is transported also changes the nature of the overall impact. Internationally, sea freight tends to have a lower impact than air freight. Once the shipment arrives at our shores, rail miles tend to be less impactful than road miles.
How the material or product is packed for transport is important too; essentially transporting air, because products don’t stack easily, for example, is highly wasteful - but it’s also the kind of information a manufacturer is unlikely to make readily available to a specifier.
Ultimately, being transparent about, and accountable for, specification decisions is key, especially when you are seeking to label a project as sustainable. It helps to try and work with manufacturers and suppliers to better understand these issues, in order to help drive improvements in the supply chain.
Of course, sustainability encompasses a variety of different considerations that goes far beyond transport and local sourcing.
The durability and adaptability of buildings is a significant one, ensuring their lifespans can be maximised before we must think about deconstructing them. And then, if a building must be deconstructed in 60- or 100-years’ time, can its components be reused as part of another construction project, in order to minimise the demand for new materials and products?
This kind of resource efficiency is essential for the built environment to make its contribution to wider net zero goals. In some cases, that might make it desirable to specify a material that has to travel further than a local equivalent.
A good example might be structural timber, about which there is often discussion in terms of sourcing from within the UK. As a country, we have relatively little land available for growing trees, so we are a significant importer of timber. The way in which timber grows in the UK is also different, so not only is there a limited quantity available but it also has different performance properties.
Efficient design and use of wood could mean that more people can make use of UK-grown timber, but only if that product offers the right performance characteristics. If Scandinavian timber is stronger, so you need less of it to create a more resilient building with smaller foundations, the overall impact is likely to be lower even though the primary structural material had to come from further away.
The impact of local sourcing and travel distances is different for every construction product, so there is no ‘one size fits all’ answer to the questions raised in this post. For many materials and products, the environmental impact of raw material extraction and processing is so great that any savings made due to ‘local sourcing’ criteria are likely to be insignificant to the bigger picture.
Where designers and specifiers are being careful to keep environmental impact to a minimum across every aspect of a project, then travel distance is going to be a much bigger proportion of embodied and whole life carbon. In such situations, opting for local sourcing where possible will have a more noticeable effect on the project’s overall claims to sustainability.
Of course, it stands to reason that not specifying exotic materials that are in limited supply, and which are only available from other areas of the globe, is a generally sustainable approach to take. Where there is no choice but to select products with more travel miles than desirable, the key is to look for responsible sourcing rather than local sourcing, necessarily.
Sustainability extends to the way in which people and communities in other countries are treated. Local sourcing can support local economies, while responsible sourcing can demonstrate the supply chain traceability that ensures people elsewhere are treated appropriately and with fairness. Regardless of any trade-offs needed between local and global sourcing, the exploitation of land, resources, and people, cannot be considered sustainable in anybody’s book.