Annie Grey explores how the construction sector can become more sustainable through the adoption of natural materials.
Photo by The Blowup
“Over the next 40-years, the world is expected to build 230 billion square metres in new construction – adding the equivalent of Paris to the planet every single week,” wrote Dr Fatih Birol, Executive Directors of the International Energy Agency, in a 2017 report.
Buildings emit more energy-related carbon globally than the entire transport sector (30% against 28%), with large amounts of that carbon being burned on site; only 6% of the UK population heat their homes with electricity from renewable energy sources. Buildings in the US currently represent 35-40% of the country’s energy consumption, and a similar percentage of national carbon emissions.
To mitigate the environmental impact of construction at this scale, the sector has the opportunity over the short and long term to actively aim to reduce emissions of carbon dioxide. We’ve seen increased attention of both companies and governments, globally, in assessing the environmental performance and material of buildings, in a bid to create a more sustainable end product.
A Sustainable Alternative Resource?
An increase in the use of wood products is thought to be part of the solution, as wood is a renewable resource than can contribute to sustainability in the construction industry. Due to its immediate association with deforestation, at first glance it may be difficult to think of wood as a sustainable material, but man-made construction materials such as concrete and steel have a large carbon footprint, causing far greater environmental damage.
In fact, manufacturing wood products requires very little external energy input. As an example, 80% of the energy consumed by Sweden’s sawmills derives from biofuels from their own production lines, such as bark and shavings, though just 20% comes from electrical energy. When manufacturing other construction materials, such as concrete or plastic, the starting point is always finite raw materials. Both extraction and processing require energy, often in very large quantities and from fossil fuels.
Not only is wood from a natural resource, but the material’s properties also enhance energy efficiency over the building’s lifecycle due to its natural cellular structure. Simply put, homes and buildings require less energy to maintain heating and cooling, plus wood can help control humidity levels to some degree. Even at the end of its lifecycle, when exposed to natural climate conditions, wood will break down much quicker than its less sustainable alternatives – concrete, steel, plastic – whilst replenishing the soil in the process. However, by optimising the conditions for the wood, the lifespan of the building can easily surpass the lifespan of the tree.
A Carbon Negative Building Material
The manufacture of cement generates substantial carbon emissions, as do the processes for making steel, meaning that all construction materials produced by these processes have a positive carbon footprint. In contrast, wood from managed forestry actually stores carbon as opposed to emitting it, through the absorption of CO2 from the atmosphere. A cubic metre of wood contains around a tonne of CO2 (more or less, depending on the species of tree), which is comparable to 350 litres of gasoline. As well as removing more CO2 from the atmosphere than it adds through manufacture, by replacing carbon-intensive materials such as concrete or steel, the contribution to lowering CO2 is doubled.
As research from the Committee on Climate Change on the uses of ‘Biomass in a low-carbon economy’ concluded:
“the greatest levels of [greenhouse gas] reduction from biomass currently occurs when wood is used as a construction material… to both store carbon and displace high carbon cement, brick, and steel”
Between 15% - 28% of new build homes in the UK annually use timber frame construction, capturing upwards of 1 million tonnes of CO2 annually as a result. Increasing the use of timber in construction could triple that amount, the report concluded.
Can Chopping Down Trees Actually Restore Carbon Levels?
There have been calls for tree planting on a massive scale to capture CO2 and control climate change, which seemingly counteracts the proposal of wood as construction material. However, both are viable options in limiting environmental damage through excess carbon.
Research has shown that while young trees are effective carbon sinks, the same cannot be said for mature trees. The Earth maintains a balanced carbon cycle: trees grow using carbon, but when they eventually fall and die, the carbon is released again. Many pine trees in managed forests take roughly 80 years to reach maturity, being net absorbers of carbon during the years of growth. Once maturity is reached, the trees shed roughly as much carbon as they absorb through the decomposition of needles and fallen branches. In fact, Canada’s great forests have emitted more carbon than they absorb since 2001 due to mature trees no longer being actively felled.
Respectively, the most beneficial form of carbon reduction is to chop down trees to restore sustainable managed forests and repurpose the resulting wood as a building material. While the appeal to not rely on the world’s forests for building demands is well-intentioned, the advantages of wood as a building material, outweighs other products on the market when looking at the environmental impact and performance.
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