Figure 1.2 Global material flows, by type, 1945 versus 2015
Biomass materials dominated in buildings until the latter half of the 20th century.
Source: Haas et al. 2020.
We Used to Build with Low-Carbon Materials
Even in the very recent past, building materials were not always carbon intensive.
Given the increasingly furious pace and scale of the global construction boom, the challenge of shifting away from carbon-intensive materials and methods often seems daunting and potentially impossible. But it is important to recall that even in the very recent past, building materials were not always carbon intensive. Up until the mid-20th century, global material flows were extracted overwhelmingly from renewable, biological sources such as forests and agricultural processes (see Figure 1.2). The vast majority of building materials were locally sourced, and buildings were specifically designed with climate conditions in mind.
Biomass materials — including wood and timber — dominated global construction, alongside earth-based materials, until the latter half of the 20th century. It has only been in the last several decades that the majority of building materials come from extractive, toxic, non-renewable processes. By the late 20th century, a preponderance of metals and minerals constituted the most-used building materials for the first time in human history. Just three materials — concrete, steel and aluminium — are responsible for 23 per cent of overall global emissions today (GlobalABC, IEA and UNEP 2018). With cooperation across global sectors, we can alter this path. The shift towards properly-managed biobased materials could lead to a compounded emissions savings in the sector of up to 40 per cent by 2050 in many regions.
To enable the shift towards new methods, it is important to understand what drives the decisions being made at each phase of the built environment process. Building materials carry enormous cultural significance. The reasons that societies choose to build with certain materials over others are complex and are driven by diverse social, technical and economic factors. Common carbon-intensive materials such as bricks, concrete, steel and glass are responsible for the image and cultural currency of cities, institutions and houses. They reflect how a community has organised over time and what it has valued during different periods of its history. Inside buildings, where modern society increasingly spends the most time, interior finishes such as wood, plaster and ceramics define the “look and feel” of how people experience their homes and workplaces, with significant implications for health and well-being.
