Wooden Skyscrapers: Has the Revolution Arrived?

Wooden Skyscrapers: Has the Revolution Arrived?

Written by Oscar Holland, CNN

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.

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

A handful of newly built timber structures will be demolished or reopened in 2020. HoHo Vienna, a mixed-use development just five feet shorter than the Mjøstårnet, has exactly open for business in Austria. And while Europe has traditionally led the toll, North America is catching up fast.
In Vancouver – a city that is already home to a 174 feet high wooden residence for students – Pritzker Prize-winning architect Shigeru Ban designed a “hybrid” condo complex consisting of a steel and concrete core with a wooden frame that will open this year. Meanwhile in Milwaukee, Wisconsin, work on the 238-foot wooden block, Ascent, will begin in June.

Climate economy

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.

The construction and operation of the buildings is due to 40% of world energy consumptionand approximately one third of greenhouse gas emissions. But while concrete releases huge amounts of carbon, trees instead absorb it throughout their lives.
Designed by Acton Ostry Architects, the student residence of the University of British Columbia Brock Commons Tallwood House in Vancouver is 174 feet high.

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

If these trees then become solid wood, this carbon is “locked” or sequestered, instead of returning to the atmosphere when the tree dies. Studies show that 1 cubic meter of wood can store more than a ton carbon dioxide.
Developers of an apartment complex in Milwaukee, for example, claim that the use of timber is equivalent to taking 2,100 cars off the road.

“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.”

Cost counting

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?

According to architect Michael Green, a longtime supporter of – and designer of – wooden buildings, there are currently “a whole bunch of things.” But since his 2013. Ted talk, in which he predicted an impending “revolution” in timber construction, a particularly significant change occurred: the price.
Digital visualization of a 35-storey prototype wooden building, Proto-Model X, developed by Michael Green Architecture and Sidewalk Labs.

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.”

Price has always been a “barrier,” Green said. Take the 10-story design of SHoP Architects, which won a government tender to occupy a site in the Chelsea neighborhood of New York, only to be missed due to worries above its market feasibility. Or Framework, the ambitious 148-foot wooden tower in Portland, Oregon, which was previously the tallest wooden tower in the United States canceled against the background of the costs associated with last year.

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.

Researchers from the Australian University of New South Wales (UNSW) recently graduated 18-month study comparing a tall timber building with a concrete and steel equivalent. According to Philip Oldfield, an associate professor at the university’s Faculty of Environment, the findings show that timber construction remains slightly more expensive to produce in terms of material costs.
A prefabricated panel is being assembled during the construction of the Brock Commons Tallwood House in Vancouver.

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.”

Legal restrictions

Designers like Green now dare to dream big. Together with Sidewalk Labs, a company owned by the parent company of Google Alphabet, the Canadian architect proposed to transform a a river neighborhood in Toronto with about a dozen wooden buildings between 10 and 35 stories in size.
On the other hand, the British company PLP Architecture has created proposals for three wooden skyscrapers, including a 984 feet high tower in the heart of London. Meanwhile, the Japanese company Sumitomo Forestry said it plans to spend 600 billion yen ($ 5.6 billion) to build the 1148 feet tall wooden skyscraper in 2041 to mark its 350th anniversary.
Digital depiction of PLP Architecture's bold proposal for a 984-foot-tall tower in the heart of London.

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 latest update to the International Building Code (IBC), which many states and states use as a basic model for their own regulations, will allow wooden buildings to grow to 18 floors for the first time. The decision is important, given that before 2018, when it becomes Oregon the first state of the United States to allow 18-story wooden buildings, nowhere in America is anything higher than six allowed.

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.

The most controversial issue remains the danger of fire. The National Association of State Fire Marshals, for example, opposed the recent update of the International Building Code, citation lack of necessary fire tests, among other problems. A statement from the organization said the changes were the result of “professional judgment” rather than science, adding that allowing larger wooden structures “without proper testing and justification” was “premature and would significantly affect the environment.” extinguish the fire. “
The concrete industry is also a vocal critic. According to Build by force, an American coalition formed by the National Association for Precast Mixed Concrete, cross-laminated timber is “an unproven material that poses great fire risks, especially in high-rise construction.” In addition to fears of deforestation, the group says sprinklers are ineffective in preventing the spread of flames through wooden buildings. He also quotes research assuming that exposed CLT panels could lead to “re-ignition and regrowth” of fires.

Proponents of bulk timber, however, say it’s not only safe – it’s actually preferable because the wood burns in a more predictable way.

Studies also show that a seven-inch-thick CLT floor has a fire resistance of two hours, which the U.S. Department of Agriculture’s Department of Agriculture says will “address concerns about the fire resistance of timber buildings and help bring them to new heights.” On the other hand, steel is prone to sudden collapse, Elgsaas said. At certain temperatures, it can “lose its load-bearing capacity and turn into spaghetti.”
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.

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.”

Research shows that being in an organic environment can have a number of health benefits. A Austrian studyfor example, they found that students in wooden classrooms were calmer and slept better than those in rooms built with traditional materials.

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.

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 ‘.

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