Global potential for material substitution in building construction: the case of cross laminated timber

The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes the vastest amount of natural resources. Widely considered a hard-to-decarbonise sector, improvements in buildings and construction are of fundamental importance for national and global targets to combat climate change. At material level, mitigation opportunities exist in terms of efficiency (using less of the same material) and substitution (using a different material). This article investigates the latter, with a global focus on the use of cross laminated timber to replace concrete floors in steel structural systems. This approach, whilst innovative, does not require any technological development nor upskilling of current professional practice, thus making it an immediately viable solution to accelerate decarbonisation. We combine Material Flow Analysis with Life Cycle Assessment across both spatial and temporal dimensions, accounting for different levels of uptake of the proposed hybrid construction in the next 30 years. Results show that greenhouse gas emissions saving potentials range between 20-80 Mt CO2e (95% confidence interval) with an average around 50 Mt CO2e in the case of full uptake of the hybrid construction system by 2050. Our analysis does not account for carbon sequestration potential in timber, which would make the savings much greater. Still, the overall savings represent a 1.5% reduction of the annual greenhouse gas emissions generally attributed to construction, thus making it a non-trivial contribution to progress towards global targets of net-zero carbon buildings