Wood is making a comeback in construction, bringing many benefits

In Japan, miyadaiku Learn about an ancient type of woodwork that is used to build temples. They believe that the characteristics of the trees and the intentions of the miyadaiku must coexist in harmony; they are as one.

It takes years to miyadaiku become Toryo – master carpenter – if they ever get there. Only one in 100 apprentices achieves that status.

The trade is protected: knowledge is transmitted orally, nothing is written. Learners learn by observing and doing. TO Toryo restoring a pagoda in 2021 will find unity with the miyadaiku who built the structure in 800 AD Even the tools, axes, and spear planes haven’t changed for centuries.

In 1934, this process enabled the Nishioka family to restore the world’s oldest wooden building, Hōryū-ji in Nara. Built in 708 AD, it took the family 51 years to dismantle the old beams and tiles, restore them, and rebuild everything.

More than 1,400 years after the construction of Hōryū-ji and wood remains the only sustainable building material that the construction industry has widely available. Despite all the advances in technique and technology, reinforced concrete and super-strong steel, some believe that only wood can help prevent a climate disaster.

The environmental footprint of construction is huge. The sector generates 38% of the world’s energy-related CO2 emissions. Concrete production worldwide is responsible for 9% of industrial water use each year.

The global stock of buildings is expected to double in area by 2060, which is the equivalent of adding one New York City every month for 40 years. So it’s time for the industry to take a good look at itself in the reflection of a glass skyscraper.

“We believe that buildings should do more to counteract their negative environmental consequences,” says Alysia Baldwin, architect at the global design practice Perkins & Will.

The firm has designed Earth Tower, a 40-story building in Vancouver. When complete, it will be the tallest hybrid wooden tower in the world. Its lateral stability will come from reinforced concrete elevator cores, but the floor slabs, walls and columns will be made from locally made solid wood.

For the construction industry to reach net zero by 2050, direct CO2 emissions from buildings must be reduced by 50 percent within a decade, estimates the International Energy Agency.

Wood must become the new standard to achieve this, says Gavin Tadman of the UK Structural Wood Association: “Wood is carbon negative from cradle to grave.”

Studies have shown that one cubic meter of cross-laminated wood (CLT) captures around one ton of CO2. [CLT is layered wooden boards stacked together like Jenga pieces and glued for stability.] In comparison, concrete emits 150 kg; steel emits 1.85 tons.

Researchers from the University of Washington found that a CLT building, from resource extraction to construction, uses 26.5% less energy than its concrete equivalent.

As a natural thermal insulator, wood performs 15 times better than concrete and 400 times better than steel, so less energy is required to heat a building.

An engineered wood frame is also around 30 percent lighter than a concrete or steel equivalent, which means less heavy machinery is required, both in transport and on site, helping to speed up constructions. . For Dalston Works, a 10-story mixed-use development in London’s Hackney, which is built with CLT, 111 freight trucks were needed, compared to 700 that would have been required for a concrete version of the building.

Wood is carbon negative from cradle to grave

When the world’s tallest wooden building, Mjøstårnet, was erected in Brumunddal, Norway, it was built without external scaffolding, despite being 85.4m high.

Precast elements were brought to the site, explains Rune Abrahamsen, CEO of Moelven Limtre, the company that produced the laminated timber structures (wooden laminates that are glued together and used for floor beams or trusses) used in construction. “The building was assembled on four floors at a time, with a total of five construction stages.” A crane helped put the larger components in place.

Wooden buildings are also receiving elevators from elsewhere. In 2018, the World Festival of Architecture introduced a category of wood as part of its annual awards, for example. Hours could be spent gawking at the participants: the wide Finnish spruce hull of the Helsinki Central Library, Oodi; the 45-meter-high hourglass observation tower spiraling out of the woods near Copenhagen (main image, above); or sunlight streaming through the four wooden pavilions of the Pingelly Cultural and Recreation Center in Western Australia (below).

Building a human connection

Studies have shown that spending time in wooden buildings can be relaxing. Research from Canada suggests that they have stress-reducing properties similar to those of nature.

A university in Finland even considered how people react to different forests. Glued laminated birch, old oak, oak trunk and gray oak were found to be “beautiful”, generating positive emotions. Finely sawn fir, laminate, oriented strand board (similar to plywood), and lacquered oak parquet were less popular.

Currently, the choice of wood is generally left to the architect, with many selecting locally sourced native materials from sustainably managed forests.

“Fir is mainly used in Mjøstårnet, both for plywood structures and for CLT panels,” says Abrahamsen. Pine was chosen for the exterior as it can be pressure treated, making it stronger and more resistant to termites.

Alysia Baldwin of Perkins & Will often opts for Douglas fir because its “reddish color gives a beautiful warmth to a space when exposed.”

[Timber] is one of the most promising innovations in construction

Mass lumber, however, is not without its critics. The Sierra Club, a US environmental organization, notes that the alleged benefits of swapping concrete or steel for wood are misleading when the impact of logging on forests is left out of the emissions equation.

Calls for the establishment of a Forest Carbon Trust, to better protect forests, particularly “primary forests”, those that are not cut down and include old trees.

“Forests must be managed to optimize the amount of carbon they store regardless of ownership, and not for the fastest return on investment,” reads a Sierra Club report on the subject. Wherever logging takes place, more climate-friendly forests are a must, is the report’s “inescapable conclusion”.

The age of wood

“Wood is the new concrete,” said Alex de Rijke, director of the London-based firm dRMM Architects, which has pioneered the use of wood in construction. speaking in 2015. “The seventeenth century was the stone age. The 18th century was the heyday of brick. The 19th century was the age of iron. The 20th century was the century of concrete. The 21st century will be the time for wood ”.

Six years later, De Rijke’s prediction seems to come true. The U.S. International Building Code is expected to allow wooden structures up to 18 stories high starting this year, while any new buildings for the 2024 Paris Olympics less than eight stories must be done. completely made of wood. Across France, there are plans for all new public buildings to use at least 50 percent wood in their construction.

What is the main perception that still needs logging? Fire safety. Following the Grenfell Tower disaster in London in 2017, the UK government banned wood and other combustible materials from the exterior of residential buildings over 18 meters high. He now proposes both continuing and expanding the ban.

Architecture critic Rowan Moore recently wrote about the decision in the British press: “It is better, you probably think, to be safe than sorry. But this precaution comes at a cost, and that is, it will impede one of the most promising recent innovations in construction. “

Organizations, including architects. Climate Action Network and the Royal Institute of British Architects are urging the government to reconsider. Part of the problem is that legislation doesn’t adequately distinguish between a building’s cladding or exterior skin and its structure, Moore says.

Testing in the USA has shown that gypsum-coated CLT lasts nearly 60 minutes longer in a fire than is required by regulations. Firefighters often consider wood-based fires to be more predictable – wood maintains its structure longer than metal and does not emit toxic chemicals.

While caution about what is a rapidly developing technology is sensible, advocates of wood have pointed out that no material is perfect: steel buckles, cracks in concrete, wood burns.

Fire resistance can be improved by encapsulating combustible materials in non-combustible materials like gypsum board and cavity barriers, Tadman notes.

European design codes for timber structures are also currently being revised, which will result in even safer buildings, believes Abrahamsen of Moelven Limtre, the plywood company.

The 20th century was the century of concrete. The 21st century will be the time of wood

And that’s the crux, the knot in the wood: wood is likely to be the future. But it still needs protection from both an environmental and construction perspective.

The central pillar of the Hōryū-ji temple pagoda was made from a single Hinoki (Japanese cypress), felled in 594 AD. It has survived lightning and a 7.2 magnitude earthquake.

The great ToryoTsunekazu Nishioka believed that due to its painstaking restoration in 1934, the Hōryū-ji Temple will now stand for at least another 2,000 years.

“Hinoki has his own Hinoki life,” he wrote in his book. Ki no kokoro, Tree minds. “Life is longer than that of iron and concrete.”

Main image: Denmark’s Camp Adventure Tower spirals out of the woods near Copenhagen. Credit: Rasmus Hjortshøj