Surrounded by agricultural land and with a population of less than 10,000 people, the Norwegian city of Brumundal may seem like an unlikely environment for record high growth.
But towering over neighboring Lake Mjøsa, more than 100 kilometers north of Oslo, the 280-foot-tall Mjøstårnet Tower became the tallest timber building in the world when it opened last year.
The 18-storey structure contains apartments, office space and aptly named Wood Hotel. And in addition to putting a small town on the world map, he added to the growing body of evidence that timber can provide a sustainable alternative to concrete and steel.
Reaching 280 feet in height, the Mjøstårnet became the tallest timber building in the world when it opened last year.
Credit: Full Architect AS / RicardoFoto
“To get attention, you have to build a tall one,” said Øystein Elgsaas, a partner in architectural practice behind the record tower, Voll Arkitekter, in a video call.
“And when you have the world’s tallest wooden building, everyone says, ‘Wow, what’s going on in Norway?’ “”
“People are interested, and that’s actually the most important part of this building – to show that it’s possible, and to inspire others to do the same.”
The record feat was achieved thanks to a type of engineered wood called cross-laminated timber, or CLT. Part of a larger group of materials known as solid wood, it is produced by gluing strips of laminated wood together at a 90-degree angle to each other before they are compressed into huge beams or panels under extreme pressure.
The resulting wooden towers – sometimes called “sliders” – were once the reserve of conceptual designers. But thanks to changes in building regulations and a shift in attitudes towards the material, they are fast becoming a reality.
The tallest tower of the HoHo Vienna project in Austria reaches 276 feet. Credit: HoHo Vienna / Michael Baumgartner / KiTO
Proponents of bulk timber argue that these towers are faster to build, stronger and, perhaps most surprisingly, safer in the event of a fire than existing options. It is possible, however, that it is their green credentials that explain the growing popularity of wood in recent years.
Designed by Acton Ostry Architects, the student residence of the University of British Columbia Brock Commons Tallwood House in Vancouver is 174 feet high. Credit: Acton Ostry Architects / Michael Elkan
“Trees store carbon, so if you collect them at the right age, when they can’t absorb much more or grow much farther, then it’s a better solution to use them as a building material,” Elgsaas said, adding that if buildings are designed with longevity in mind, they could protect carbon from the atmosphere for generations. “It prolongs the life of trees (before they decompose) by maybe 100 or 200 years, if done correctly.”
Cross-laminated timber has been used for low-rise buildings in European countries such as Germany and Austria since the 1990s, and the environmental benefits of using bulk timber have long been known.
So why the recent rise in interest?
Digital visualization of a 35-storey prototype wooden building, Proto-Model X, developed by Michael Green Architecture and Sidewalk Labs. Credit: Sidewalk Laboratories / Michael Green Architecture
As bulk timber becomes more widespread, more and more CLT factories are being built and economies of scale are reducing prices.
“There is more knowledge in the market, more competition, more supply chains … At the time of my conversations with Ted, there was no real infrastructure,” Green said by phone. “Gradually, as more competition was seen, the price went down.”
However, the price of cross-laminated timber has declined in recent years and is now “on par” with traditional materials, Green said. Similarly, Elgsaas said that the developer behind the Mjøstårnet tower in Norway found that the final amount was “approximately the same” as an alternative to steel and concrete.
A prefabricated panel is being assembled during the construction of the Brock Commons Tallwood House in Vancouver. Credit: Acton Ostry Architects / Pollux Chung
But the savings can be found in other ways, he said in a telephone interview. In particular, the possibility of assembling or factory building wooden components means that other construction costs may fall.
“If you can do it faster and open the building faster, you don’t have to borrow money that long and you can get a faster return on investment,” said Oldfield, who is also the author of the 2019 book. The Sustainable Tall Building: Primer Design “, adding:” What we are finding is driving timber, there are fewer sustainability benefits and more benefits for contractors and customers. “
For Green, the real tipping point will come not when timber is just as cheap – but when it is cheaper.
“We are not where (the timber is) cheaper,” he said. “And we want it to be cheaper, because at the end of the day, that’s what drives the whole industry – the cheapest solution.
“We need to address climate change by making things more accessible, not by wanting people to suck it up and pay more because it doesn’t work.”
Digital depiction of PLP Architecture’s bold proposal for a 984-foot-tall tower in the heart of London. Credit: PLP architecture
But while these architects clearly believe in the structural potential of bulk timber, there are still many practical barriers to the implementation of such projects: building regulations.
The changes will take effect in 2021 – although they are only advisory. Some countries, such as Norway, already have height restrictions, while other countries and states may choose stricter building codes than those set out in the IBC.
And limited data remains on how large wooden towers will respond in the long run to a variety of risks, from extreme weather to termites and wet.
Proponents of bulk timber, however, say it’s not only safe – it’s actually preferable because the wood burns in a more predictable way.
The main tower of the Sara Cultural Center in Skellefteå, Sweden, will become one of the tallest solid wooden structures in the world when it opens in 2021. Credit: White Architect
Green compares bulk wood to a large log set on fire – it doesn’t capture light right away and burns slowly once it’s done.
“In the event of a major catastrophic fire, in general, if you ask firefighters to enter a heavy timber building opposite a steel building, they are more likely to enter the (former) one,” he said. “Because even though the beams are charred, they can quickly tell how much charm, and therefore how much residual wood, there is.”
Regulations invariably lag behind technology, Elgsaas added, with each completed tower helping to allay concerns about efficiency and safety.
“The more buildings we see pushing the limit, the easier it will be to propose new building codes and raise the bar on what is possible,” he said.
Change of culture
With the changes in the regulation, there will be a transformation in the cultural attitude towards wood, Green claims. While the shift to timber architecture may be the most fundamental change in the way we build skyscrapers since the early 20th century, in places with a long tradition of wooden buildings, such as Northern Europe or North America, it may be more -less revolution and more renaissance,
“Before we built big, giant wooden buildings in North America and around the world, we really stopped when concrete came along,” Green explained, adding that large city fires stifled the material’s enthusiasm. In the 1840s, the invention of reinforced concrete in New York, Pittsburgh, St. Louis and Toronto was ravaged by flames that quickly spread through densely packed wooden frame buildings.
“There were big big fires in the city and we naturally said, ‘Well, don’t build with combustible materials anymore’ (…) We knew we could build these big buildings, but we just stopped talking about it.”
Related Video: Japan’s National Stadium with Wooden Roof Opens Ahead of Tokyo 2020 Olympics
In hypermodern cities with a short history of wood construction, such as Shenzhen or Dubai, for example, there may be limited enthusiasm for its return. Winning developers and architects over this, Green argues, should revolve around what he sees as advantages in timber design.
“The paraphrasing of the notions of what modernity is, what forms should be, what makes people more comfortable and what makes the quality of space better, should be related to human problems – to feel less stressed, to be more healthy, more productive, faster learning, he said. “These should be the defining principles of good design.”
Elgsaas also testifies to the psychological benefits of the tree. He describes the open wooden columns of Mjøstårnet, with their organic appearance and various grain patterns, having a certain character that homogeneous concrete simply cannot achieve.
“People who live, stay and work there say it feels much cleaner, in a way,” he said.
Challenges ahead of you
Despite growing enthusiasm for wooden high-rise buildings, long-term environmental challenges remain. On the one hand, if bulk wood will achieve its projected carbon savings, the trees used must be harvested from sustainable forests, Oldfield told UNSW.
“If CLT is going to be a major building material for us for the next 30 years, we must now start planting trees,” he added. “We looked at how much timber we would need if, by 2050, say, 30% of the new buildings were made by CLT – and we’re talking about growing a brand new forest of 100 by 100 kilometers.
“And there are big questions about whether you should build such forests at all, because they are monocultures, while natural forests have biodiversity.”
Japanese company Sumitomo Forestry plans to spend 600 billion yen ($ 5.6 billion) to build a 1,148-foot wooden skyscraper in 2041 to mark its 350th anniversary. Credit: Sumitomo Forestry Co., Ltd.
Oldfield’s research also raises another long-term question that needs to be addressed: What happens to the carbon released when a building is eventually demolished, even if it is decades or centuries later? И това ли отменя предимствата на използването на материала на първо място?
“Ако погребете дървените елементи и те се разпаднат – или ако изгорите сградата в края на живота й – вие изпускате този въглероден диоксид обратно в атмосферата”, каза той.
Решаването на тези въпроси е за следващите години и десетилетия. Засега обаче изглежда, че скъпоструващите разработчици обмислят многото възможности на материала. Архитект Елгсаас заяви, че дървеният материал се е оказал най-подходящ за Mjøstårnet – но той държи на открито как може да се построят небостъргачите на бъдещето.
“Не вземам страни – не съм дървен или пробетон”, каза той. “Смятам, че е важно да използваме подходящия материал за правилната работа.”
Тази статия беше актуализирана с подробности за проекта в Торонто на Sidewalk Labs ‘.