Timber has hit the mainstream in Australia with significant timber towers at various stages of design and construction around the country, and local supply capacity expanding to meet the anticipated appetite of our region.
Among the many reasons why project teams are choosing to build with timber, perhaps the most influential factor relates to the material’s inherent sustainability.
We’re not talking about timber’s low thermal conductivity or the value of a panellised timber façade to achieve Passive House certification. We’re talking about the carbon absorbed by trees during their growth which is then locked away in the timber structures we build.
In this article we look at how to easily work out the amount of carbon stored in any timber building, and where your project sits on the sustainability spectrum.
You may be familiar with the process of photosynthesis in which plants take carbon dioxide from the air and water from the ground and combine these with sunlight to create the energy they need to grow fibre.
As you read this there is about 1 million hectares of plantation softwood trees growing around Australia, making up less than 1 per cent of our total forested area.
This represents a massive amount of CO2 locked away from the atmosphere, so why should these trees be harvested? As trees mature their growth slows, as does their consumption of CO2. By harvesting the mature trees and replacing them with saplings we are effectively turbocharging this incredible, natural, CO2 removal machine, fuelling our construction industry and driving our economy all at the same time.
Decades of experimentation have allowed the timber industry to identify a range of species which offer fast growth and high strength.
While all trees utilise CO2 in their growth and a wide variety of timber species are suitable for construction, decades of experimentation have allowed the timber industry to identify a range of species which offer fast growth and high strength.
So, we know every tree in a plantation is a veritable carbon sink, but doesn’t the energy required for harvesting and milling a tree offset this benefit? Timber processing certainly looks like a highly industrial task that involves very large machines, noisy trucks, long conveyor belts, sharp saws and cavernous kilns.
In fact, the process of turning round logs into rectangular studs does require a massive amount of energy, but interestingly this generates relatively small amounts of emissions and waste.
How? Well, the large energy demands of your typical sawmill often cannot be supplied by the electrical grid in the rural communities in which they are typically found. Often sawmills turn to on-site energy production, utilising solar, wind or biomass burner production methods to generate their own power and reduce their impact and reliance on the local power grid.
This may sound like a lot to consider, and a whole heap of work for anyone who just wants to know the amount of carbon locked up in their timber building. Surely there must be an easier way?
Enter the Environmental Product Declaration (EPD). EPDs are a standardised and verified way of quantifying the environmental impacts of a product. A material’s EPD provides metrics which measure the environmental impact of a product’s production (cradle to gate) and sometimes beyond.
WoodSolutions hosts a library of free, generic timber EPDs produced in partnership with Australia’s timber industry.
While EPDs are typically supplier specific, WoodSolutions hosts a library of free, generic timber EPDs produced in partnership with Australia’s timber industry.
Think of your house – for the sake of this exercise, let’s assume it is a three-bed, single-storey, timber-framed brick veneer.
The building has about 12 cubic metres of structural softwood used in the wall frames, floor joists and roof trusses.
WoodSolutions’ revised Softwood Timber EPD shows a cradle to gate environmental impact of minus 718 kilograms of CO2eq per cubic metre of timber, meaning the timber in your house is storing more than eight tonnes of CO2 – roughly equivalent to the emissions produced by your car over two years of driving.
It is easy to be intimidated by the complexity associated with sustainability and emissions, but EPDs can make things easier.
Armed with this information you can readily compare the environmental impacts of different building materials, and quickly calculate the real amount of carbon sequestered within your timber structure.
For more information on the environmental impacts of a variety of structural timber products, as well as other valuable resources, visit the WoodSolutions resource library.