CTI Blog - Why Build In Wood?
This article is by Paul Brannen, MEP for the North East England Region. It originally appeared on www.northeastlabour.eu
Historically timber has been used to build homes, especially one and two storey buildings. Taller and larger buildings have been possible with timber frames but above 5 or 6 storeys is rare.
However, relatively new engineered timber products such as Cross Laminated Timber (CLT) and Laminated Veneered Timber (LVL) have the structural strength of steel and concrete, enabling wooden framed buildings to now be built to much taller heights and on a much larger scale.
These new products have enabled the construction of the world’s tallest wooden building, Tallwood House at Brock Commons East, on the campus of the University of British Columbia in Vancouver, Canada. It is 53m tall with 18 floors - you can watch it being constructed in under 3 minutes here.
Wooden buildings even taller than this are currently under construction including the HoHo building in Vienna, Austria which will have 24 floors, see here, and a Japanese company are planning on building the world’s tallest wooden skyscraper. Other wooden skyscrapers are being built or are planned across the globe.
There are many benefits to be gained from building in engineered wood, including:
Building in wood can see a floor a week being constructed on site, as the wooden panels are constructed off site in factory conditions. This is twice as fast as concrete. Overall wooden buildings can be up to a third faster to build reducing construction site costs i.e. the hired crane is there for less time.
Timber is a renewable and sustainable product when managed and produced in an environmentally friendly way. Construction timbers, such as CLT, LVL and Glulam, are made with a non-toxic adhesive and can be made with little or no burning of fossil fuels unlike steel, brick and block which all need large amounts of heat to produce and they tend to derive this heat from the energy produced from burning fossil fuels. The actual chemistry involved in making cement for concrete results in large amounts of CO2 being released. Theoretically this could be captured (Carbon Capture and Storage - CCS) but to date it has not happened.
Sequestration of Carbon
While trees are growing they sequestrate carbon from the air. In fact trees could rightly be described as CCS ´machines´. When trees are turned into timber products the timber still continues to sequestrate the carbon for the life time of the wooden product, hence timber is a natural “carbon sink”.
Tall and/or large steel and concrete buildings have large carbon footprints. Comparable wooden buildings can have a reduced carbon footprint of 60-75% in comparison.
The importance of substituting for steel and concrete
Concrete and steel have large carbon footprints. One of the primary ingredients in concrete is cement and to make cement you need to heat and grind up limestone or a similar material. In addition to the energy required in the manufacturing process, the U.N calculate approximately 1 ton of carbon dioxide is emitted per ton of cement produced. As concrete is the second-most consumed substance on the planet, after water, cement production accounts for as much as 8 percent of human-produced carbon dioxide emissions.
Concrete and steel are both heavy to transport involving large numbers of lorries that in turn generate exhaust fumes that contribute to poor air quality especially in our cities and they also burn fossil fuels exacerbating climate change.
Wooden buildings can be five times lighter than a steel and concrete equivalent meaning transport costs both financially and environmentally are reduced. Lorry deliveries to the construction sites where wood is the principal building material can be reduced by 80% because wood is lighter and needs fewer lorries to move it. As wood is lighter this can also reduce the groundwork (foundation) costs.
A 125m high building made from wood could have a 75% lower carbon footprint than one made from steel and concrete.
50% less energy is used to manufacture wooden rather than concrete buildings and only 1% of the energy needed to produce steel.
During construction wooden buildings produce less dust and their construction is quieter, which is good news in urban areas.
Following construction in cold climates the estimated energy consumption and carbon emissions for CLT buildings are 9.9% and 13.2% lower than those of reinforced concrete buildings in view of life-cycle assessment; see here for more information.
Currently using building methods centered around, concrete, steel, brick and block, the building sector is responsible for 42% of final energy consumption, 35% of total greenhouse gas emissions, 50% of extracted materials and 30% of water consumption in the European Union. Construction and housing have a fundamental role to play in enhancing societal goals for sustainable growth, see here.
Wooden interiors deliver a multiple of physiological and psychological benefits including:
- reduced blood pressure, heart rate and stress levels
- improvements to a person’s emotional state and level of self-expression
- improved air quality through humidity moderation.
Renovation and Refurbishment
As a light-weighted material that can be processed easily, wood is the ideal material for renovation and refurbishment, allowing high flexibility for inhabitants and users to adjust buildings to specific needs.
Cost; Timber/CLT v concrete/block/steel
A question often posed is whether building in wood is cheaper than building in a material such as concrete. To help answer this question, Building magazine undertook a price comparison in June 2017 and noted:
“We have prepared two detailed cost models, one each for a CLT and concrete design for a seven-storey private residential building. The scheme has been designed with both a timber and concrete solution in mind at the outset, with a structural layout to suit both.
“…the construction cost variance between timber and concrete for this hypothetical scheme is minimal. The higher CLT superstructure costs are offset by the ability to reduce pile quantities because of a lighter frame, hence a saving on substructure. The CLT programme for the frame and upper floors is around 10–15% shorter than the concrete option, resulting in a lower preliminaries cost.”
The cost of wooden buildings can be kept down by pre-fabricating panel sections in factory conditions where they can be made to the millimetre, meaning that there’s little to no waste. Doors and window apertures can be pre-cut in the factory. Government figures show about a third of the materials that arrive on a construction site using concrete tend to get sent to landfill resulting in more lorries on the road.
In April 2018 Alinea Consulting produced an influential report that highlighted the advantages of using CLT over concrete. The report, Residential Timber: Cost Model, suggests CLT is a viable alternative and uses two detailed exemplar cost models to demonstrate the point.
Wooden buildings are more energy efficient meaning longer term the owners will both use less energy and pay smaller energy bills. If the CLT used is thick enough then an energy saving of 14% could occur. This is because wood has a natural thermal efficiency which means timber systems can be more cost effective in constructing energy efficient buildings than concrete, block or bricks.
Additionally, In a recent (July 2018) independent study produced by Rider Levett Bucknall (rlb.com) a comparison was made between the cost of timber frame v masonry build methods in order to determine which is more economical for affordable housing. The study found "the overall situation ... results in the timber frame solution being more economical to construct" p16. It was also "quicker".
But aren’t wooden buildings more prone to hazards and natural disasters?
Buildings made from CLT have no inherent fire risk. When brought into contact with fire the outer surface of the wood chars and then acts as a very effective insulator for the wood below. When the heat source is removed the fire goes out. Furthermore, CLT remains more structurally stable when subjected to high temperatures.
See demonstration of an attempt to set fire to CLT with a blow torch in this Economist video on wooden skyscrapers here.
Further, Silvia Melegari wrote in Revolve that CLT buildings, “have the flexibility to handle the world’s strongest earthquakes with no loss of life or structural change”.
Who is designing and building big in wood already?
Waugh and Thistleton, London: http://waughthistleton.com/
White arkitckter, Sweden: http://whitearkitekter.com/project/skelleftea-cultural-centre/
Bob BBL, Norway: https://www.bob.no/
Acton Ostry, Vancouver, Canada: http://www.actonostry.ca/
LEVER, Portland, USA: https://leverarchitecture.com/
More Information: Interesting Links and Articles
What is Cross Laminated Timber? https://www.youtube.com/watch?v=YuAya0hRjwU
The world’s tallest wooden buildings: https://www.youtube.com/watch?v=v3JqSsc8ZKk
TED talk by architect Michael Green, ‘Why we should build wooden skyscrapers’: https://www.youtube.com/watch?v=Xi_PD5aZT7Q
Innovative Wood Products Collaborative, ‘Why build with wood?’ http://www.themostnaturalresource.com/why-build-with-wood/
New Statesman, “Why wood is making a comeback in house building”, http://bit.ly/2PEXq4s
Building, ‘Cost model: residential timber’ http://bit.ly/2yPDguQ
Sustainability Open Access Journal, “A Comparison of the Energy Saving and Carbon Reduction Performance between Reinforced Concrete and Cross-Laminated Timber Structures in Residential Buildings in the Severe Cold Region of China” http://www.mdpi.com/2071-1050/9/8/1426
Revolve Magazine, Spring 2018 Issue: https://issuu.com/revolve-magazine/docs/revolve_27_digital
Benefits of Urban Trees, a FAO infographic: http://www.fao.org/3/a-c0024e.pdf
The contribution of wood-based construction materials for leveraging a low carbon building sector in Europe: https://www.sciencedirect.com/science/article/pii/S2210670716305923
Adoption of unconventional approaches in construction: The case of cross-laminated timber: https://www.sciencedirect.com/science/article/pii/S0950061816313514
Cost gap between CLT and concrete is narrowing: https://www.trada.co.uk/news/cost-gap-between-clt-and-concrete-is-narrowing/
Cement Industry Urged to Reduce Invisible Global Emissions http://bit.ly/2OtyYOE