The benefits of wood construction for the climate are not pure imagination, but a significant way to sequester carbon dioxide and reduce the carbon footprint of residential areas. Markku Karjalainen, professor of Architectural Construction at the School of Architecture at the University of Tampere reveals the physical facts that make wood the best construction material.
Wood sequesters half its weight in carbon – and a log house stores it
‘When one cubic metre of wood grows in the forest, it sequesters a tonne of carbon dioxide during its growth while photosynthesis releases 700 kg of oxygen into the atmosphere. A cubic metre of wood, weighing 500 kg, binds 250 kg of carbon, meaning that about half of the weight of wood is carbon,’ explains Karjalainen.
Wood absorbs carbon dioxide as it grows even if it won’t be used for construction. It’s about storing carbon dioxide. ‘When wood is used in construction, it is stored. In other words, if the service life of the building is 60, 80 or 100 years, carbon dioxide is prevented from entering the natural cycle during that time,’ says Karjalainen.
The same result cannot be achieved with the other uses of wood. ‘If wood is made into biodiesel, pulp, paper or wood chips, the carbon dioxide will be released into the atmosphere within a few years. So, for the climate, the wisest way to use wood is construction.’
According to a global trend, the use of wood in construction is increasing due to reasons related to environmental and carbon footprint. At the moment, wood construction is extremely popular in the construction of schools and daycare centres.
Wood wins the emission competition in every construction phase
According to the Ministry of the Environment of Finland, providing emission calculations for the entire construction process already in the building permit phase will be mandatory in Finland by 2025 at the latest. This also includes a report on building materials and how much emissions their manufacture and transport produce. ‘In this respect, wood is a superior building material,’ says Karjalainen. ‘Wood is a renewable and local material, and we have plenty of it. Due to its lightness, wood is easy to transport. A cubic metre of wood weighs only about a fifth of what a cubic metre of concrete weighs.’
The lightness of wood also helps to reduce emissions during the construction phase. ‘The lightness can be utilised well in advanced prefabrication. The future trend is to use solid wood, and more and more industrial prefabrication is being moved to dry factory conditions. Spatial element construction is fast and ecological because the construction site phase is so short.’
Solid log is the most ecological frame material
The facts are eye-opening. The production of concrete creates seven per cent of the global greenhouse gas emissions. It is easy to imagine the effects if concrete were replaced with wood in construction whenever possible. In reality, we will not reach this situation, but we must use wood for all possible construction.
‘Even though concrete production generates emissions, it is still needed in construction,’ points out Karjalainen. ‘As are steel, glass, aluminium and insulation materials. These materials will still be required. But in many cases, we can replace concrete with wood. According to a global trend, the use of wood in construction is increasing due to reasons related to environmental and carbon footprint. At the moment, wood construction is extremely popular in the construction of schools and daycare centres.’
Particularly the use of solid wood in on the increase. ‘Solid wood structures are the future. In other words, in the construction of large sites, whether they are care facilities or schools, daycare centres or wooden high-rises, the material will be solid wood. Log construction is even more environmentally friendly than balloon-frame construction due to the larger amount of wood.’
More wood in all construction
Karjalainen has many new uses for solid wood: ‘Wood could be used, for example, in bicycle and pedestrian bridges, noise barriers, park benches and lamp posts. The use of wood could be significantly increased.’ The professor, who specializes in wood construction, points out that the importance of environmental issues will grow even further. We must be able to construct more ecological buildings so that the building materials are locally sourced, preferably renewable natural materials. In addition, we should make an effort to build more densely. This is the vision for the future, and we are headed in this direction.’
Solid wood structures are the future. In other words, in the construction of large sites, whether they are care facilities or schools, daycare centres or wooden high-rises, the material will be solid wood.
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