Wooden Skyscrapers: Has the Revolution Arrived?

Wooden Skyscrapers: Has the Revolution Arrived?

written by Oscar Holland, CNN

Surrounded by farmland and with a population of less than 10,000 people, the Norwegian town of Brumunddal may look like an unexpected setting for a record high altitude.

But the height of the Mjøstårnet tower, which is 280 feet high and up to 280 feet high, became the tallest wooden building in the world when it was opened last year.

The 18-storey building contains apartments, office spaces and the conveniently named Wood Hotel. In addition to placing a small town on the world map, it has added to a growing body of evidence that wood can provide a sustainable alternative to concrete and steel.

Mjøstårnet reaches 280 feet, and became the tallest wooden building in the world when it opened last year.

Mjøstårnet reaches 280 feet, and became the tallest wooden building in the world when it opened last year.
credit: Voll Arkitekter AS / RicardoFoto

“To get attention, you have to build long,” Øystein Elgsaas, an engineering partner behind the tower Voll Arkitekter, said in a video call.

“And when you have the tallest building in the world made of wood, everyone says,” Wow, what’s going on in Norway? “”

“People are interested, and this is actually the most important part of this building – to show that it is possible, and to inspire others to do the same.”

This benchmark achievement was achieved thanks to a type of designed wood called interlocking wood, or CLT. Part of a larger group of materials known as collective wood, produced by gluing strips of plywood together at 90-degree angles to each other, before being pressed into massive bundles or panels under extreme pressure.

The resulting wooden horoscopes – sometimes called “plyscrapers” – were once protected by concept designers. But thanks to changes in building regulations and shifting attitudes toward materials, they quickly became true.

The tallest tower in the HoHo Vienna project in Austria is 276 feet. credit: HoHo Vienna / Michael Baumgartner / KiTO

A large number of new high-rise timber buildings were set to break the road or open in 2020. HoHo Vienna, a multi-purpose project five feet shorter than Mjøstårnet, has Open to work in Austria. And while Europe has traditionally led this charge, North America is catching up quickly.
In Vancouver – a city already home to Student residence, wooden, 174 feet long – Architect Shitzu awarded the award-winning Pritzker award Apartment complex “Hybrid” It consists of solid core and concrete with a wooden frame that will open this year. Meanwhile, in Milwaukee, Wisconsin, work on a 238-foot-tall wooden residential building, Ascent, is scheduled to begin in June.

Climate economics

Collective woodland defenders claim that compared to the options available, these towers are faster to build, stronger, and perhaps more surprisingly, they are safer in case of fire. However, it may be their green credentials that explain the growing popularity of wood in recent years.

Building construction and operation calculations 40% of the world’s energy consumption, And about a third of greenhouse gas emissions. But while concrete emits a large amount of carbon, the trees instead absorb it throughout their life.
Designed by Acton Ostry Architects, student residence at the University of British Columbia Brock Commons Tallwood House, in Vancouver, it is 174 feet high.

Designed by Acton Ostry Architects, student residence at the University of British Columbia Brock Commons Tallwood House, in Vancouver, it is 174 feet high. credit: Acton Ostry Architects / Michael Elkan

If these trees are then converted into collective wood, the carbon is “locked” or isolated instead of being returned to the atmosphere when the tree dies. Studies show that 1 cubic meter of wood can be stored More than a ton Of carbon dioxide.
For example, the developers of the Milwaukee’s Ascent Apartment Complex, Demands Its use of wood is equivalent to driving 2,100 cars off the road.

“Trees store carbon, so if you collect them at the right age when you can’t absorb more or grow a lot more, it’s better to use them as building materials,” said Al-Jassas, adding that if the buildings were designed with consideration to longevity, they could keep carbon out of the atmosphere for generations. “It extends the life of trees (before decomposing) maybe 100 or 200 years, if done correctly.”

Calculate the cost

Laminated wood has been used in low-rise buildings in European countries such as Germany and Austria since the 1990s, and the environmental benefits of using group wood have long been known.

So why the recent rise in interest?

According to architect Michael Green, a long-time advocate and designer of wooden buildings, there is “a whole bunch of things now converging.” But since then 2013 Ted talking, In which a coming “revolution” in woodbuilding was foreseen, there was one particularly important shift: cost.
Digital visualization of a 35-storey wooden building, Proto-X model, developed by Michael Green Architecture and Sidewalk Labs.

Digital visualization of a 35-storey wooden building, Proto-X model, developed by Michael Green Architecture and Sidewalk Labs. credit: Sidewalk laboratories / Michael Green Architecture

With the increase in the spread of collective woods, more CLT factories are being built and economies of scale reduce prices.

“There is more knowledge in the market, more competition and supply chains … At the time of TED’s talk, there was no real infrastructure,” Green said by phone. “Increasingly, as we’ve seen more competition, the cost is going down.”

Green said prices have always been “a hindrance”. Take the 10-storey SHoP Architects design, which won a government competition to occupy a site in the Chelsea area of ​​New York, to be dropped only because of Worries On the viability of the market. Or Framework, an ambitious 148-foot tall wooden tower in Portland, Oregon, is set to be the tallest wooden tower in the United States by canceled Amid cost worries last year.

However, Green said, the cost of interlocking wood has decreased in recent years and is now “on par” with conventional materials. Likewise, Elgsaas reported that the developer behind the Norwegian Mjøstårnet tower found that the final amount was “almost” as an alternative to steel and concrete.

Researchers at the Australian University of New South Wales recently completed Study for 18 months Comparing a tall wooden building with the equivalent of concrete and steel. According to Philip Oldfield, associate professor at the university’s built-up college of environment, the results show that timber construction is still marginally more expensive in terms of material cost.
A pre-made board is lifted into place while building the Brock Commons Tallwood House in Vancouver.

A pre-made board is lifted into place while building the Brock Commons Tallwood House in Vancouver. credit: Acton Ostry Architects / Pollux Chung

He said in a telephone interview that savings could be found in other ways. In particular, the ability to pre-fabricate, or build wooden factories, means that other construction costs may decrease.

“If you can make it faster and open the building faster, you won’t need to lend money as long as you can get a return on investment faster,” said Oldfield, who wrote the book 2019 in the title of “A Tall Tall Sustainable Building”. Primer Design, adding: “What we find driving wood is the least sustainable, and most beneficial to contractors and clients.”

For Green, the real turning point will not come when wood is equally cheap – but when it is cheaper.

“We are not at a point (timber) cheaper,” he said. “And we want it to be cheaper because in the end, that’s what rules the entire industry – the cheapest solution.

“We have to solve the problem of climate change by making things within reach, not by asking people to absorb it and pay more, because it does not work.”

Legal restrictions

Designers like Green now dare make a big dream. In partnership with Sidewalk Labs, a parent company of Google Alphabet, Canadian architect suggested converting A riverside neighborhood in Toronto With about ten wooden buildings, the length ranges between 10 and 35 floors.
Elsewhere, the British company PLP Architecture has created proposals for three wooden skyscrapers, including Tower height 984 feet In the heart of London. Meanwhile, Japan’s Sumitomo Forestry says it plans to spend 600 billion yen ($ 5.6 billion) to build A wooden skyscraper with a length of 1,148 feet In 2041 marking the 350th anniversary of its founding.
Digital display of the bold PLP proposal for a 984-foot tower in the heart of London.

Digital display of the bold PLP proposal for a 984-foot tower in the heart of London. credit: PLP Engineering

But while these architects clearly believe in the structural possibilities of collective wood, there are still very practical barriers to achieving such projects: building regulations.

Last updated To the International Building Law (IBC), which many US states and states use as the basic model for their own regulations, will allow wooden buildings to rise to 18 floors for the first time. The decision is important considering that before 2018, when it became Oregon The first American state To allow 18-story wooden buildings, no place in America allowed anything higher than six.

The changes will take effect in 2021 – though they are only advisory. Some countries, such as Norway, already have lower height restrictions, while other countries and American countries may choose stricter building codes than those specified in IBC.

There is still limited data on how, in the long term, large wooden towers respond to a variety of hazards, from severe weather to termites and moisture.

The most controversial question remains the fire danger. For example, the National Association of State Fire Chiefs opposed the recent update of international construction law, according to Lack of required fire test, among other concerns. The organization said in a statement that the changes were the result of “professional judgment” and not science, adding that allowing larger wooden structures “without proper testing and justification” is premature and will affect the environment of extinguishing fires significantly.
The concrete industry was also a strong critic. to me Build strongly, An American alliance formed by the National Precast Concrete Association, laminated timber is an “unstable material that poses significant fire hazards, especially in high-rise construction.” In addition to concerns about deforestation, the group says the sprinklers are ineffective in preventing fires from spreading through wooden buildings. He also quotes Research This indicates that exposed CLT panels can lead to “re-ignition and regrowth” of fires.

However, supporters of collective wood confirm that it is not only safe – it is actually the best, as wood burns in a more predictable way.

Studies also showed that the CLT floor is 7 inches thick Fire resistance for two hours, Which the USDA’s Department of Forestry says “will address concerns about the fiery performance of wooden buildings and help lift them to new heights.” Al-Jassas said that steel, on the other hand, is subject to sudden collapse. At certain temperatures, it can “lose its carrying capacity and turn into spaghetti.”
The main tower of the Sarah Cultural Center in Skellefteå, Sweden, will become one of the tallest large wooden structures in the world when it opens in 2021.

The main tower of the Sarah Cultural Center in Skellefteå, Sweden, will become one of the tallest large wooden structures in the world when it opens in 2021. credit: White Arkitekter

Green compares large woods with a large log placed on campfire – does not immediately catch light, and burns slowly as soon as it occurs.

“In a big catastrophic fire, in general, if you ask firefighters to enter a heavy wooden building in exchange for a steel building, they prefer to go to (the first),” he said. “Because although the beams are charred, they can quickly tell how much coal is, and therefore how much of the wood remains,” he said.

Al-Jaas added that the regulations always fail to technology, as each completed tower helps to alleviate concerns about effectiveness and safety.

“The more buildings we see exceeding the limit, the easier it will be to suggest new building codes and raise the level of what is possible,” he said.

Culture transformation

With shifts in regulation, there will be a shift in cultural attitudes towards wood, says Green. While the transition to wooden architecture can represent the fundamental change in how skyscrapers are built since the early twentieth century, in places with long traditions of wooden buildings, such as Northern Europe or North America, they may be less revolutionary and more uplifting.

“We used to build huge, giant wooden buildings in North America and around the world, but we really stopped when the concrete appeared,” Greene said, adding that large-city fires reduced enthusiasm for the materials. In the 1840s, the contract was invented in which reinforced concrete, New York, Pittsburgh, St. Louis and Toronto, was destroyed by fires that quickly spread through buildings with crowded timber frames.

There were some big city fires, and of course we said, “Okay, let’s not build combustible materials anymore” (…) We knew we could build these big buildings, but we stopped talking about them. “

Related video: Opening of the Japanese National Stadium with Wooden Roofs before the 2020 Tokyo Olympics

In hyper-modern cities with little history of wood building, such as Shenzhen or Dubai for example, there may be limited enthusiasm for its return. Greene argued that winning developers and architects should be about what he sees as the advantages of wood design.

“Reformulating the concepts of what modernity is, what forms it should be, what makes people more comfortable, and what makes space quality better, it must be linked to human issues – feeling stress, health, productivity, and learning faster,” he said. “These should be the specific principles of good design.”

Research has suggested that being in an organic environment can have a number of health benefits. a Austrian Study 2010For example, I found that students in classroom rooms were more relaxed and sleeping better than students in rooms created with traditional materials.

Plaster also attests to the psychological benefits of wood. He describes the exposed wooden beams of Mjøstårnet, with their organic appearance and various grain patterns, as possessing a certain character that uniform concrete cannot achieve.

“The people who live, live and work there say it looks a lot cleaner in some way,” he said.

Next challenges

Despite the growing enthusiasm for tall wooden buildings, long-term environmental challenges remain. For example, if mass wood is to provide its purported carbon savings, the trees used must be obtained from sustainable forests, says Oldfield of the University of New South Wales.

He added: “If CLT was going to be a major building material for us in the next thirty years, we need to start planting trees now.” “We looked at how much wood we needed if by 2050 for example, 30% of new buildings were made from CLT – and we’re talking about planting a whole new forest with an area of ​​100 x 100 km.

“And there are big questions about whether you should even build forests like these, because they are mono cultures, while natural forests have biodiversity.”

Japan's Sumitomo Forestry plans to spend 600 billion yen ($ 5.6 billion) to build a wooden skyscraper with a height of 1,148 feet in 2041 to mark the 350th anniversary of its founding.

Japan’s Sumitomo Forestry plans to spend 600 billion yen ($ 5.6 billion) to build a wooden skyscraper of 1,148 feet in 2041 to mark the 350th anniversary of its founding. credit: Sumitomo Forest Company Ltd.

Oldfield’s research also raises another long-term question that needs to be addressed: What happens to carbon sequestered when a building is ultimately demolished, even if after decades or centuries? Does this negate the benefits of using the materials in the first place?

“If the wood elements are buried and decomposed – or if they burn the building at the end of its life – then you will leak carbon dioxide into the atmosphere,” he said.

Addressing these questions is for years and decades to come. But for now, low-cost developers seem to be exploring the potential of multiple materials. Architect Elgsaas said wood has proven to be the best fit for Mjøstårnet – but it keeps an open mind on how to build skyscrapers in the future.

“I do not support any side – I am not a supporter of wood or a supporter of concrete,” he said. “I think it is important that we use the right materials for the right job.”

This article has been updated to detail the Toronto Sidewalk Labs project.

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