How does the use of wood in buildings influence the impact on climate change?

The sustainable arguments for wood construction are many. The construction industry is one of the biggest contributors to the negative climate impact and building in wood can save us a lot of carbon emission. Then why don’t we use more wood? The biggest challenges are the lack of knowledge and hands-on experiences. Political and legal matters also make it more difficult, time consuming and expensive to choose wood and timber solutions.

As green building has evolved beyond its initial emphasis on operational energy efficiency, greater attention has been given to the choice of structural materials and the degree to which they influence a building’s environmental impact. Wood is the only major building material that grows naturally and is renewable. The use of wood from sustainably managed forests also offers significant benefits when compared to materials that require large amounts of fossil fuels to manufacture.


Wood is able to replace other construction materials


Wood can replace other construction materials in many structures while providing the same functionality. One example is that in the Swedish bridge standards (Hästepallarna) wooden bridges can be designed for the same function and service life as steel and concrete bridges. Such a material substitution could bring significant climate benefits, where wood replaces materials whose production requires fossil fuels and causes high carbon emissions. A study has shown that where wood products replace other construction materials in buildings, there is an estimated average substitution factor of 1.6 tonnes carbon dioxide per cubic metre of wood material, which in an industrially produced apartment with a wood frame adds up to 16 tonnes of carbon dioxide. With greater energy efficiency drives and more climate-smart building, the production phase and thus material choices will take on greater significance, and substitution options will be important.


Hästepallarna Wooden pedestrian and cyclist bridge in Sweden.


Fitting several vertical webs and horizontal Glulam (glued laminated timber) beams together allows the box cross-section to be built up. The beams are bound together with adhesive and transverse stays. The webs can be manufactured with a camber to give the bridge a gently curved shape. Box beam bridges have high stiffness and thus are able to handle longer spans.

The deck is sealed with a weatherproofing layer plus asphalt or gravel. Box beam bridges are often made in one as they can have spans of 30 m. The design and surface treatment is performed in line with the relevant bridge standards and the service life of such a bridge is 80 years.


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. 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 newbuilds, 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.


Sources: BuildingGreen & SwedishWood

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