Wood in buildings: the right answer to the wrong question

Reducing the embodied emissions of materials for new construction and renovation of buildings is a key challenge for climate change mitigation around the world. However, as simply reducing emissions is not sufficient to meet the climate targets, using bio-based materials seems the only feasible choice as it permits carbon storage in buildings. Various studies have shown that bio-based materials allow turning overall life cycle impacts negative, therefore, having a cooling effect on the climate. In recent years, scholars and policy makers have focused almost exclusively on the advancement of wooden buildings. Timber structures stand out as they can be prefabricated and used for high-rise buildings. Yet, one important aspect seems to be overlooked: the consideration of supply and demand. Large forest areas that allow sustainable sourcing of woody biomass only exist in the Northern hemisphere, notably in North America and Europe. In these regions, though, urbanization rates are mostly stagnating, meaning new construction rates are low. The largest amount of material requirements in these regions are derived from the refurbishment of the existing stock. Moreover, in areas where structural material is needed for new construction, in Asia, Africa and South America, rain forests need to be protected. Therefore, we need to rethink the desire to find one solution and carelessly implement it everywhere. Instead, we need to consider locally available material and know-how for grounded material choices. This paper explores the supply of a range of bio-based materials and matches it against the material demand of global building stocks. It is based on various previous studies by the authors, of South Africa, China, Portugal, and more. The analysis divides between structural materials for new construction, such as wood and bamboo, and thermal insulation materials for the refurbishment of existing buildings, such as straw and hemp. The results emphasize the need for diversifying bio-based material solutions

Dynamic life cycle assessment of straw-based renovation: A case study from a Portuguese neighbourhood

Action is needed to mitigate climate change. As the building sector is one of the main contributors to energy consumption, renovation of existing buildings is a key strategy. However, for a drastic greenhouse gas emissions (GHG) reduction, sensible material solutions are required. Bio-based products seem to be a promising alternative thanks to carbon sequestration in the new biomass, which needs to be regrown for substitution. The conventional life cycle assessment (LCA) framework seems unsuited to model temporal emissions and carbon uptake of such solutions. Dynamic LCA (DLCA), which models temporal aspects, is more appropriate to evaluate the environmental performance of bio-based products. Moreover, the different dynamic drivers of urban building stocks should be included to allow for informed material choices. A new methodology is proposed, integrating DLCA with material flow analysis (MFA) considering a dynamic renovation rate. The global warming potential over time of the thermal retrofit of a Lisbon neighbourhood with a straw-based technology is assessed. The results highlight the importance of the end of life scenario, greatly influencing the results in the mid- to long term. Increased renovation rates can yield higher carbon storage benefits. However, if accompanied by technological solutions that rely on carbon intensive materials, e.g. finishing, this can lead to increased embodied carbon emissions in the transition period

Speeding up post-disaster reconstruction: material choice or roof design?

The consequences of urbanization and climate change are dangerously converging. The most affected populations are the urban poor, settled in informal settlements, vulnerable to increasingly frequent disasters. This severely contributes to the existing housing gap of the affected regions, already struggling with housing demand. The speed of shelter delivery becomes key for an efficient response. The present study aims to understand the impact of material choice on postdisaster shelters delivery through a multiscale analysis of their construction speed. The scales considered for the study are: Constructive technology, Shelter Unit and Post-disaster settlement. At the scale of the Constructive technology, nine different solutions suitable for the Nepal earthquake reconstruction are compared, covering a range from local to industrialized. Successively, twelve different shelter designs delivered worldwide by the International Federation of the Red Cross have been studied under the same lens, at the Shelter unit scale as well as for the case of the Post-disaster camp. The study shows that a clear correlation between material procurement and speed can be identified at the element scale. This correlation becomes secondary at the shelter scale, where it is visible that materials play a limited role in affecting the construction time, that is mainly driven by the complexity of the roof design. Moving to the settlement scale, the procurement choice of materials seems to be impacting the speed again. The study indicates how no univocal solution fits for the three different scales of the study, providing efficient guidelines for post-disaster reconstruction. Beyond that, it highlights that effective construction can be developed with a variety of materials, but its emergency responsiveness can seriously be compromised by a non-appropriate design

Speeding up post-disaster reconstruction: material choice or roof design?

The consequences of urbanization and climate change are dangerously converging. The most affected populations are the urban poor, settled in informal settlements, vulnerable to increasingly frequent disasters. This severely contributes to the existing housing gap of the affected regions, already struggling with housing demand. The speed of shelter delivery becomes key for an efficient response. The present study aims to understand the impact of material choice on postdisaster shelters delivery through a multiscale analysis of their construction speed. The scales considered for the study are: Constructive technology, Shelter Unit and Post-disaster settlement. At the scale of the Constructive technology, nine different solutions suitable for the Nepal earthquake reconstruction are compared, covering a range from local to industrialized. Successively, twelve different shelter designs delivered worldwide by the International Federation of the Red Cross have been studied under the same lens, at the Shelter unit scale as well as for the case of the Post-disaster camp. The study shows that a clear correlation between material procurement and speed can be identified at the element scale. This correlation becomes secondary at the shelter scale, where it is visible that materials play a limited role in affecting the construction time, that is mainly driven by the complexity of the roof design. Moving to the settlement scale, the procurement choice of materials seems to be impacting the speed again. The study indicates how no univocal solution fits for the three different scales of the study, providing efficient guidelines for post-disaster reconstruction. Beyond that, it highlights that effective construction can be developed with a variety of materials, but its emergency responsiveness can seriously be compromised by a non-appropriate design