The study investigates the environmental benefits of reusing Cross Laminated Timber (CLT) panels. The Global Warming Potential (GWP) of a single-stored Coffee shop built in 2016 in Kobe city was calculated, considering different CLT reuse ratios, forest land-use and material substitution possibilities. The results showed that as the rate of reused CLT panel increases the total GWP decreases. Moreover, in all cases, the option with smallest GWP is when the surplus wood is used for carbon storage in the forest, revealing the importance of a growing forest for increasing the environmental benefits of timber utilisation. The results suggest the systematic reuse of CLT panels offers a possibility to increase the carbon stock of Japanese Cedar plantation forests and further mitigate the environmental impact of construction.
Prefabrication of timber envelope components is a constantly developing research field, which attracts interest from various sectors of expertise thanks to the conspicuous advantages it can confer in terms of resources savings, as well as quality management and safety for all actors involved in the process...
This report presents an overview into cross laminated timber (CLT) as a construction material and how it compares to traditional methods of construction. CLT is also examined in the context of a move to off-site manufacturing (OSM) and a greater emphasis on sustainability in the construction sector. In this context it is found to perform well with mass timber products such as CLT being the only carbon negative building materials capable of building mid and high-rise buildings.
The barriers and opportunities for CLT are explored looking at literature, industry reports and case studies. The main barriers to wider use of CLT still come from uncertainties around the material. Although they have been proven to not be a problem, worries over issues such as how it performs during fires and the lifetime of buildings persist. A lack of standardisation may be the primary cause for this as a range of products and specifications across different manufactures and countries creates confusion and means that each building needs to be individually specified. The opportunities identified for CLT include its carbon saving properties which could benefit governments wanting to reach their carbon reduction targets. In addition, the ability to use CLT on a wider range of sites such as unstable brownfield land and over service tunnels lends to its strength in aiding with urban densification.
In terms of costs, these are found to be comparable to those of traditional construction methods with high material costs being offset by reduced foundations and construction time. CLT buildings do, however, face a premium in insurance costs. Transport costs, resulting from a concentrated production base in central Europe, also add a considerable amount to the overall cost of the finished product. This in turn encourages domestic production in countries outside of Europe.
The possibilities for CLT in the UK residential construction market are investigated with a focus on mid-rise and high-rise flat construction as that is what the economics and material properties of CLT most lend itself to. Although CLT currently has a low market share of less than 0.1% of homes in this sector there is the potential for this to increase to 20-60% over time. The lower range of this estimate is not predicted to be reached before 2035 and this is also dependant on rising CLT production levels. The volume of timber that is needed to manufacture enough CLT to reach these increased construction volumes can be sourced sustainably from existing forests production in Europe and North America. In addition, the UK has enough excess timber harvesting capacity to provide for the entirety of CLT buildings in the UK, however, large scale domestic CLT production is required to make this a reality.
Cross-laminated timber (CLT) construction is a relatively new process. There is therefore very little specific technical documentation for the erection of structures designed and built with CLT panels. Current CLT manufacturers provide recommendations on lifting systems for the installation of prefabricated wood assemblies. However, technical documents currently available mostly come from Europe or Canada and may appear incomplete to some design professionals and builders/contractors in the United States. This Chapter presents a variety of lifting systems that can be used in the construction of structures using CLT panels. We discuss the basic theory required or suggested for proper lifting techniques. In addition, we introduce various tools and accessories that are frequently required for CLT construction, as well as good building practices to help contractors build safe and efficient CLT panel structures. Finally, we discuss issues related to the transportation of CLT assemblies from factory to building site. Regulatory aspects of transportation are also discussed. It is importat to note that the lifting, handling, and installation of CLT panels involve multiple interest groups including design professionals, contractors/erectors and CLT manufacturers, each with different areas of interest and expertise. Therefore, the information presented in this Chapter is broad in scope and may or may not be relevant to each interest group.