Cross Laminated Timber is a possibility for a more sustainable future, but to make it more widespread we need to increase production facilities and teach architects how to build with wood.
Helsinki, Finland/Oregon, USA. February 21st 2021. Global housing will have to double, as more citizens will need a place to live in the urbanized centers. How to imagine a world where construction has to increase and Co2 emissions decline, while respecting the housing demand of a growing population? What if the way we imagine the city has to radically change? The Swedish company Stora Enso, along with others in the field, is working on the answer: «we started producing CLT in 2008, in Austria, in one of our mills» explains Sabrina Bartl, head of PR International. CLT is short for Cross Laminated Timber, a type of engineered wood made out of layers of lumber glued together. First invented in the ninety-nineties, it has played a key role in wood production ever since. This method of manufacturing wood panels allows to create a material that is «stable and stiff» and could replace steel and concrete as the main materials used in building. Stora Enso is now the largest CLT provider in Europe, having exceeded one million cubic meters produced in 2019. The company already has three CLT mills, and is planning to launch a fourth by 2022.
Building and pollution
Construction accounts for thirty-nine percent of global carbon emissions. According to Stora Enso, Co2 production might be cut up to seventy percent by using CLT wood panels instead of steel and concrete. When dealing with climate change, «in the public eye nobody is thinking about construction – they are thinking about transports, such as cars or air traffic – but they only account for the two percent of the whole Co2 emissions globally». Things have been changing in the past few years and «the public is understanding that construction is one important part of the climate discussion». This is turning into practical help from the institutions as well and «the industry now gets support from the EU and we are seeing many cities starting to think about wood as a construction material».
Construction with CLT
The main issue the industry still has to face is that the majority of architects and engineers are not trained to design and build with wood rather than massive materials yet: «for architects and builders these days building with wood is still very uncommon and still very unknown. So it is a huge step for them to change from building with steel and concrete to designing a building with wood». Knowing the difference and studying wood-building in detail is essential to be able to build with CLT: «It’s different to plan and design a building made in wood because the process is different: the planning is quite strict and you have to think about things that are happening on the construction site already when you are planning the building – for example where should the electricity go». When building with concrete and steel, decisions tend to be made in process on the construction site. With wood buildings, instead, everything has to be planned and decided at the stage of the first design. If this makes things more complicated at the beginning, it also speeds up the actual construction activity. Stora Enso estimates that the erection can be up to seventy percent faster, «which is quite logical because you don’t have to wait for the drying periods or weather conditions. You don’t need so many workers there, so you’re quick». Builders also «get complete walls or floors elements, and in the exact right order. You get all the elements from the truck, and you just have to take them and put them together as in the plan». In order to do so, the company designed an app based on the use of QR codes: «each element has its QR code, and the app that’s available to everyone on the construction site. They can go there, scan the element, and then they see in the app exactly where the element goes». The process is also aided by using a 3D model of the building, made in collaboration with the architect, rather than just paper plans, that often risk getting ruined and can end up compromising the construction.
Building Concepts
To tackle the lack of preparation for architects that would otherwise be open and willing to design wooden buildings, Stora Enso came up with Building Concepts, a service with which they provide guidelines to professionals that want to approach CLT construction. «We want to eliminate the hurdles for architects who have never built with wood and want to start designing with it» Bartl explains, «it’s an open source and it has guidelines with ideas on how to build specific types of buildings. We have one building concept for residential, one for offices and we are just launching a building concept for schools». In addition, «all of those concepts were created together with our partners, construction companies, with structural engineers, architects, and so on». According to Bartl, the way to go is to make CLT visible and desirable as a building material – with this goal in mind they are launching «a new content platform about all that we try to tell – to architects, planners, designers, construction companies, NGOs, communities, politicians, but also to consumers – and it’s called ‘Let’s talk about the Wood House Effect’».
The aesthetics and biophilic design
Mike Lipke, president of Trillium Pacific Millwork, in the United States, offers a different perspective: «we normally provide smaller panels, mainly made for interiors, for people to show how the building is made inside». Trillium Pacific, unlike Stora Enso, mainly sells standard-measures panels, made for decorative purposes. This introduces another aspect of CLT: the aesthetics. In the case of CLT, the right word to use, Bartl says, is «biophilic, meaning the closeness to nature within a building». Indeed, a building that is made of wood, studies show, especially as for the interiors, tends to restore a connection with nature that is not present in traditionally-build structures. Buildings made with CLT seem to have a grip on the senses. According to Bartl, «when you are entering in a wooden building, the first thing is that you smell it, always, even after years, you still smell the wooden scent». The reaction of people walking into a wooden space are different, but «when you are observing people entering a wooden building for the first time they always go to a wall and touch it – it is some kind of natural way for us to connect with that even when we are in a building: to touch and feel and smell the wood. And that ultimately lowers stress levels and slows down the heartrate». Lipke confirms that «we have seen an increase in the interest in the panels, as more and more buildings are constructed in CLT we had more demand for our products as well – and I just see that continuing to grow and have even more buildings built by using this technology».
Challenges ahead
Though «we have seen a new CLT production facilities being opened quarterly», one of the challenges that still lie ahead is the potential insufficiency of mills should the demand further increase: «the only downside in the USA is that we still don’t have enough production facilities – if all buildings went to wood construction we would probably not be able to supply all of the material that we would need in the short term and it would take some time for the capacity to catch up with the demand». Many states also still have strict regulations about wood construction. In some places it is still not allowed to construct high buildings. «There are building codes that have to be followed and that’s the big hurtle to overcome for CLT construction, because in the past it has not been a common way to construct buildings and so some of the building codes haven’t changed yet – so that’s a lot of change that has to happen in order for CLT to catch on and spread». Yet, some architects, like Michael Green, are indulging in the idea that limitations will soon be overcome, and it will be possible to live in cities where even skyscrapers are made of wood, and we can construct sustainable buildings that lower emissions and can store Co2. In this context, his project Empire State of Wood is a symbol to get the idea, showing how it would be possible to have the Empire State Building entirely made of wood. The Empire State is the representation of a dream come true – what if the next dream we realize is made of wood?
Stora Enso
With more than 700 years of activity, Stora Enso produces very resistant 5-layers CLT panels, sustainable solutions for building and packaging.
Trillium Pacific Millwork
Trillium Pacific Millwork is a wood production company based in Oregon, USA. They produce all kinds of wood. CLT is a part of their production, but they mainly make small 3-layers panels for interior design decorations
