The role of construction materials in the move to net zero

Sustainable use of building materials is key in order to reduce the greenhouse gas emissions in construction. Certain materials are highly rated in terms of sustainability credentials and, while these sustainable resources should be favoured under all circumstances, it rarely happens that one solution fits all when it comes to material choice in projects. The right products need to be selected for the right building based on type, size, location, usage, and lifetime expectancy, making intelligent and efficient material use necessary to build sustainably.

Timber for example, is an inherently sustainable and a renewable resource. Timber sequesters carbon during tree growth and, when used in buildings, it locks this sequestered carbon within the building. It is a structural solution with significantly lower upfront embodied carbon emissions than concrete or steel. Targeting a reduction in upfront emissions is especially important because it's released before a building even opens its doors and can equate to 38-55 per cent of a low-energy building's whole life carbon emissions, according to the London Energy Transformation Initiative (LETI).

According to the Timber Accord, building 200,000 new houses in timber would store around 4 million tonnes of carbon dioxide each year, equivalent to the carbon emissions of approximately 2.4 million London to New York return flights.

Timber structures still come with some complexities in the UK, so checking the fire regulations and warranties that are applicable to the size and use of the building, but also acoustics and risks of condensation as early as possible are of paramount importance when assessing viability of a timber solution. Designing efficiently, and developing a design that responds to the timber characteristics, such as designing for smaller structural grids, is key to reducing the need for timber too.

Concrete can be the right solution for certain buildings. Efficient design, pre and post tensioned strategies, and offsite construction can contribute to using less concrete. Using ground granulated blast-furnace slag (GGBS) as a cement replacement helps to reduce concrete embodied carbon, but should only be considered as the last resort at the end of design after all possible efficiencies have been applied. This is because GGBS is a waste product from the carbon intensive steel manufacturing industry and there is just not enough GGBS for all UK projects to use it at high rates for cement replacement. Recent research by University of Dundee highlights the increasing scarcity of GGBS and calls for alternatives. The concrete industry is trying to decarbonise concrete, according to a report by Institution of Civil Engineers, so watch this space.

Steel can also be a possible alternative for appropriate buildings. Sizing accordingly, designing for adaptability, flexibility and deconstruction, and ensuring steel elements' characteristics are stored with building files (via BIM and materials passports, for example) are key to increasing the lifetime of the building allowing for extensions and/or change of use, or for these elements to be reused at the end of this building's life.

Building layers beyond the building structure can have shorter lifespans or may require frequent replacement. Use of bio-based materials and materials of high recycled content in those layers can reduce the environmental impact of a project. There is a lot of innovation taking place in this sector at the moment, with insulation products made of mycelium, furniture made of waste plastics from various post-consumer and post-industrial sources, boards and insulation made of hemp, carpet with 100 per cent recycled content, and blinds made from recycled waste plastic. Cradle-to-cradle certified products can be sought to ensure use of circular materials that are responsibly made.

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