James' World 2

Could your house take a bullet for you?

Clad it with a new type of modified wood, and it might, says Alex Lau, co-founder and executive chairman of InventWood.

The US-based company has developed Superwood – a modified wood it claims is stronger than steel.

During lab tests, a gas gun fired a bullet-like projectile at thin pieces of wood, including an early version of the company’s product.

While the projectile blasted straight through the natural wood, it failed to penetrate the heavily modified version.

Mr Lau suggests that the product could have military applications, such as in battlefield shelters, but admits they “haven’t tried dropping bombs on it”.

In the race to decarbonise construction, materials such as concrete – associated with high greenhouse gas emissions – are coming under ever-greater scrutiny.

Wood-based construction, proponents say, can actually help in the fight against climate change by storing large amounts of carbon long-term.

But natural timber is not always strong enough for certain applications and it can degrade when exposed to moisture or wood-gobbling insects.

That’s where engineered wood products come in. They promise to be significantly stronger and more resilient – reliable enough, even, to form the structural frames of skyscrapers. The construction industry is increasingly pushing wood to new limits.

“You can almost massage the wood so you’re squeezing air and imperfections out,” explains Mr Lau as he describes the process of treating timber with chemicals to remove lignin, a polymer found in wood, and then compressing it extremely firmly to reduce its volume by around 80%.

This has the effect of creating additional hydrogen bonds within the material, adds Mr Lau, significantly strengthening it even though it becomes much thinner than the original timber.

A key advantage, InventWood says, is in retaining the wood’s attractive grain in the finished product.

InventWood has spent years refining its process – it used to take more than a week. Now, staff can make a piece of Superwood in hours.

The company will use wood from poplar trees initially but Mr Lau says it’s also possible to use bamboo.

“We can grow suitable bamboo feedstock in like three or four years,” he says. “It’s really an efficient way to draw down carbon from the atmosphere.”

There are already a range of engineered and modified wood products on the market. Take glulam, or glue-laminated timber, in which layers of wood with the grain facing in the same direction are glued together to make strong, moisture-resistant beams.

Cross-laminated timber (CLT), meanwhile, involves stacking layers of wood with the grain in alternating directions, to make panels for walls and floors. Like an ultra-tough plywood.

Using CLT instead of concrete to build a community centre could reduce carbon emissions associated with the construction and operation of the building by nearly 10%, a study published in June suggested.

Superwood isn’t designed to compete with these products, says Mr Lau. But it could provide a more aesthetically pleasing, and structurally sound, finishing layer to them, for example. Or, it could function as a durable external cladding.

It’s a “promising” technology, says Morwenna Spear, research fellow at Bangor University’s BioComposites Centre.

Though she points out that, in environments such as the UK, wood that is used externally on buildings must cope with weather that cycles from wet to dry extremely frequently. “I’d want to see some data coming from them about that,” she says.

Other companies are working on different engineered wood products.

Pollmeier in Germany, for example, has BauBuche – a laminated veneer lumber, very thin layers of wood pressed and glued together – made using beech. That’s interesting because beech is not generally considered the first choice for construction.

“By processing it into veneers, Pollmeier found a way to use it much more structurally,” explains Michael Ramage, director of the Centre for Natural Material Innovation at the University of Cambridge.

There’s also 3RT in Australia, which uses thin veneer sheets of low-value trees or “pulp logs”.

It allows them to mimic the structure and density of much more valuable hardwood. The product has recently been used in large window frames and also to make kitchen cabinets, furniture and the treads of internal staircases.

With so many wood products emerging, Dr Spear says that architects and designers today have much more choice in terms of how they use wood in a building.

“It may be that we think of these new products al

most as pseudo-species,” she says. “It just increases that palette of options to people.”