A Wooden High-Rise Outside Tokyo Grows Japan’s Timber Ambitions
Aaron Clark and Eddy Duan, Bloomberg News
(Bloomberg) – This article is part of the Bloomberg Green series Timber Town, which looks at the global rise of timber as a low-carbon building material.
Less than an hour by train from central Tokyo, on a narrow tree-lined street hemmed with convenience stores, a ramen shop and a hostess club, stands a building unlike any other in Japan. The structure is a fully wooden-framed, fire-resistant high-rise.
Port Plus is a training and education facility in Yokohama built by and for general contractor Obayashi Corp., a storied Japanese builder that traces its roots back to 1892. The firm has constructed some of the country’s most iconic structures, including Tokyo Central Station, dating to 1914, and the Kenzo Tange-designed Yoyogi National Stadium 2nd Gymnasium, completed in the 1960s.
But Port Plus — which was finished last year and is composed mainly of 540 wooden rigid cross-joints that are 2.8 meters (9.2 feet) wide by 4 meters (13 feet) tall — may be its most ambitious. The structure offers a pivot away from the carbon-intensive building materials like steel and cement that dominated Japan’s postwar landscape and offers a new path for modern mass-timber construction in a country where, for centuries, wood has played a central role in temples, homes and workspaces.
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“We believe that the utilization of forest resources will lead to the realization of a low-carbon society and the revitalization of local communities,” Shinji Yamasaki, chief engineer in Obayashi’s timber construction promotion department, said in an emailed statement. The company is committed to wooden construction and actively forming alliances across the forestry industry, Yamasaki added.
Port Plus exemplifies a global shift by architects and builders, who are constructing everything from skyscrapers to wind turbines with one of the world’s oldest building materials in an attempt to reduce the climate impact of structures, which account for roughly a third of global emissions. Accelerating the shift are new engineered products such as cross laminated timber (CLT) and laminated veneer lumber (LVL), which stack layers of wood like a sandwich and are often sturdy enough to be used as structural components.
The Yokohama building’s main technical innovation is also its architectural highlight: The rigid cross-joints effectively combine traditional columns and beams into single prefabricated units, composed of LVL wrapped in multiple layers of fire-resistant plasterboard and a finishing layer of wood. Glued-in rods and nuki joints, a traditional Japanese carpentry technique, strengthen and connect the units. No adhesives are used in the larch core, so the timber can be reused at the end of the building’s life.
From the street the giant blond joints shoot up vertically and horizontally in a lattice-like pattern, punctuating a sleepy neighborhood dominated by shorter residential and commercial buildings made from concrete, steel and brick. The building’s name references the Port of Yokohama, which was one of the nation’s first trading posts to open to foreigners in 1859, and the urban center remains one of Japan’s most cosmopolitan.
Read More: Recycling Our Cities, One Building at a Time
Inside Port Plus, delicate touches amplify the structure’s biophilic design. In a seminar room, two dozen wood panels run from near the floor up and across the ceiling in a giant wave wrapping a visitor like a surfer in the barrel of a breaker. In the building’s meditation and yoga room, plants spill out from the ceiling. Many of the building’s walls are surfaced with a clay-like plaster made from materials including egg shells and a type of siliceous sedimentary rock typically composed of fossilized microalgae.
Port Plus, which was designed in-house, is intended to showcase Obayashi’s ability to construct mass-timber buildings that generate a lower carbon footprint than conventional materials. The company estimates the building’s construction generated about 2,500 metric tons of carbon dioxide equivalent, compared to 4,200 tons of emissions for a similar building made from steel and 8,600 tons for a concrete structure.
The shift to timber comes with tradeoffs, though, and buildings like Port Plus typically cost between 30% and 40% more than an equivalent structure made from steel, according to Obayashi. But clients concerned about meeting Japan’s 2050 carbon-neutral goal are driving sales, and the company says it has received orders for five timber buildings in the last fiscal year.
There is “strong demand from our clients to build this kind of building,’’ Yamasaki said in an interview.
The adoption of mass timber is also accelerating as the material is subjected to more tests that show its resiliency in the face of disaster. In May, engineers in California subjected a 10-story wood building to a series of simulated earthquakes on the world’s largest high-performance “shake table,” which uses hydraulic actuators to thrust the steel platform through six degrees of motion to replicate seismic force. The mockup survived several simulated tremblors including a 7.7-magnitude quake with no structural damage.
Another concern is how wooden buildings respond to fires. Tests conducted on full-scale mock apartments in a US federal research lab in 2017 showed that wood forms an outer char layer when it burns that slows the progression of fire and protects the wood core. Both sets of research have helped quell fears over the safety of timber high-rises as many governments see the material as a way to help meet climate targets.
Promoting timber construction is one way nations can help decarbonize their building stock and meet climate goals. Japan is aiming to cut its carbon emissions 46% by 2030 from 2013 levels and achieve carbon neutrality by midcentury. The country is still ironing out exactly how it will do that, although authorities have said they plan to issue the world’s first climate transition bond to raise up to 20 trillion yen ($133 billion) over the next decade.
Much of that money will flow to Japan’s industrial giants as they work to make everything from the country’s steel mills to its power generation cleaner. Government largesse has already been extended to Obayashi, which received 327.3 million yen in grants and subsidies for Port Plus. The company declined to disclose the building’s total cost.
Japan’s domestic timber industry could also benefit from growth in wooden buildings. Of the 1,990 cubic meters of timber used in the construction of Port Plus, about 72% originated within the country, with additional material imported from Russia and Brazil. Forests cover roughly two-thirds of Japan, and much of the wood used in the building came from thinning stands of trees to boost the health of the ecosystems, according to Obayashi.
It’s difficult to quantify the well-being benefits of architecture that utilizes natural materials, but they are easy to feel. Walking through Port Plus feels closer to visiting one of Japan’s 1,000-year-old Buddhist temples than the frenetic concrete development that covers much of Tokyo and Osaka.
One purpose of the building is to share those benefits with some of the company’s 15,876 employees when they visit Port Plus, which includes 32 accommodation units, most of which are in a rear section of the building that uses the same rigid cross joint structure but is clad in steel panels. But the structure is also a deeply ambitious statement and exploration of how architects and builders can navigate the climate crisis.
For Obayashi, the project offered invaluable lessons in sourcing, designing, constructing and fire-proofing mass timber projects.
“We learned that a building can be fully made out of wood,” said Yamasaki.