WHY CHOOSE WOOD?
Wood is a sustainable construction material
Wood is a versatile raw material and the only renewable construction material. Wooden structures are usually characterised by a combination of different components that together deliver the best possible load-bearing capacity, thermal, acoustic and moisture insulation, fire resistance and a long service life.
Increasing the proportion of wood in construction can facilitate a reduction in the use of other construction materials, such as concrete, steel and brick. These construction materials don’t come from renewable raw materials, they require a great deal of energy for their production and they entail higher emissions of carbon dioxide.
The EU’s long-term plan for a competitive economy with low carbon emissions is called Roadmap 2050. The key driver of this transition will be energy efficiency. A low carbon economy will have much greater need for renewable energy sources, energy-efficient manufacturing of construction materials, energy-efficient structures and low-energy modes of transport.
In this context, the construction sector has opportunities over the short and long term to reduce emissions of carbon dioxide through the choice of materials with a low environmental impact and through energy-efficient structures. Increasing the use of wood products is part of the solution.
Low carbon footprint
The past two decades have seen the rapid development of wood in architecture, as a result of the EU’s switch to function-focused standards in the member states’ building regulations. This now makes it possible to build larger buildings using wood-based systems.
Manufacturing wood products requires the input of very little external energy, over and above the energy from their own by-products.
The most energy-intensive stage of the process is the drying of boards and planks. This is also the stage that uses most electrical energy to run the fans in the dryers.
When manufacturing other construction materials, the starting point is always finite raw materials. Both extraction and processing require energy, often in very large quantities and from fossil fuels.
The manufacture of cement generates substantial carbon emissions, as do the processes for making steel. All the construction materials produced by these processes therefore have a positive carbon footprint.
This measure of a product or activity’s emissions of carbon dioxide and other greenhouse gases helps the user to opt for the alternative with the lowest impact on the climate. Wood is carbon negative since carbon dioxide is stored in the original wood and the emissions associated with harvesting, transport and processing are small compared with the quantity of stored carbon dioxide.
Environmentally efficient life cycle and ecocycle
All construction materials except wood have a single ecocycle that involves reuse. For wood there are two ecocycles – a shorter one that reuses the component or material, and a longer one that reuses the constituent parts of the wood material via nature’s ecocycle.
We see examples of the shorter ecocycle in the construction industry and in distribution and packaging. Windows, doors and timber can be reused, as can pallets, packaging and cable drums. In all cases, there is an organisation to deal with the products and find new users.
Once wood can no longer be reused or its material recovered, for use in fibreboard and other sheet materials for example, it can still generate energy through incineration. This energy is climate-neutral and is in fact stored solar energy.
To make optimum use of wood in climate terms, it should be carried out in a particular order that is illustrated by the environmental hierarchy for wood (see below). When choosing between different usage options, the alternative that gives the longest period of use should always be chosen, i.e. the one that is higher up the environmental hierarchy. Directly using felled forest for energy production is not optimal – although it is naturally still better for the environment than energy from finite fossil fuels. It is important to note that wood never needs to be sent to landfill.
Building with wood is positive for the climate
Achieving a climate neutral society depends on greater energy efficiency and wider use of renewable energy sources.
For the construction and real estate sector, this will have an impact on both the production and use phase. For newbuilds, this is about the choice of materials and having a construction process with a low environmental impact and an energy-efficient building at the end of it. For the existing buildings, the focus will largely be on energy efficiencies, since the environmental impact of the construction phase has already happened.
Looking forward to the year 2050, an estimated 80 percent or so of the stock in existence then will be buildings that have already been built today. These must be upgraded to make them fit for the future. It is therefore no coincidence that the greatest focus is on energy efficiencies. We have chosen, however, to present the case for new-builds, as this gives a complete picture of the system for future building design.
Historically, a building’s operational phase has accounted for the greatest energy consumption during the building’s lifetime, and the production phase has been seen as almost negligible. With the advent of new, increasingly stricter requirements concerning energy use in our buildings, and in an extreme case zero-energy buildings, energy use in the production phase will become increasingly important.
Adapting material choices, designs and production processes to the new conditions is a major challenge for the construction sector. Greater use of wood-based products and wooden structures is a significant part of the solution, due to the material’s carbon storage and substitution effects.
Forest a renewable raw material resource
Growing forest absorbs carbon dioxide from the atmosphere. This happens through photosynthesis, which converts solar energy, carbon dioxide and water into carbohydrates that are the building blocks of wood. Oxygen is released as part of the process. Through photosynthesis, a normal tree absorbs an average of 1 tonne carbon dioxide per cubic metre of growth, while at the same time producing and releasing the equivalent of 0.7 tonnes carbon dioxide. Growing forest constitutes a carbon sink, because it captures and stores carbon.
The absorbed carbon from the carbon dioxide is bound in the wood and continues to be stored in the products made from the wood. If the wood products are used in buildings, the carbon is stored for a long time. The stored carbon is only released when the products are incinerated at the end of their life. During incineration, the converted solar energy is released as heat, making the process entirely climate neutral. In our European cogeneration plants, the biomass ends up as heat and electrical energy when the bound carbon dioxide is released.