Wood in buildings: the right answer to the wrong question

Abstract

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.

The carbon dioxide storage potential of building materials: a systematic literature review

“…The category 'biomass -slow growing' contains materials like wood or timber but also cellulose fibre, cork, cardboard and construction paper. The values for the materials in this category have been reported by [8,10,[13][14][15]. The CO2 storage ranges reported for both biomass categories appear to be very similar.…”

“…Figure 2 shows that the materials in the categories 'biomass -fast growing' and 'biomass -slow growing' have the highest CO2 storage potential according to the literature. Reviewed materials for the category 'biomass -fast growing' are straw, hemp and bamboo but also miscanthus, sheep wool, herbaceous plants, moso bamboo, palm leaves and seaweed, as reported in the studies by [8][9][10][11][12][13][14][15]. An interesting new approach for growing microalgae in a CO2 off-gas stream with a CO2 storage potential of 2000 gCO2/kg is also included in this category.…”

Exploring Low-Carbon Design and Construction Techniques: Lessons from Vernacular Architecture

“…While timber buildings are promoted at a global scale, the extent to which the present and future demands of the construction industry can distress the available forests is less clear [112]. In fact, the largest forest areas allowing for the sustainable sourcing of wood building materials exist in developed countries, notably in North America and Europe, while the largest building stock growth happens in developing countries-Asia and Africa-some of which are experiencing significant population growth [11][12][13]. Accordingly, the application of timber buildings as a one size-fits-all approach to all building types may not be a solution for many developing regions.…”

“…Among all bio-based materials, wood has received the most attention [9]. In recent years, many scholars and policy makers in developed countries have mainly focused on the promotion of wood buildings, especially mass timber construction, as the key solution to reducing embodied carbon emissions from the building sector [11]. Researchers have even advocated using engineered timber to turn the global building stock into a carbon sink to mitigate the climate crisis [12].…”

“…The global building stock is expected to double in size, and the largest new building stock increase will happen in developing countries in Africa and Asia, accompanied by a population growth [13]. By 2055, Asia's population is expected to peak at 5.4 billion, while by 2100, Africa's population is expected to reach 10.9 billion [11]. In those areas with the highest population growth, the demand for wood as a primary construction material cannot be fulfilled [9].…”