It’s not quite as simple as ‘build with wood, save the rainforest’, but Michael Green believes timber-based construction can help with that, besides several other knotty 21st century problems.
Mr Green’s practice MG-Architecture (MGA) has been one of the leading lights in North American timber building since launching in 2012. He wrote the influential book ‘The Case for Tall Wood Buildings’ and has spoken on the subject worldwide, including in TED Talks, where he comes on, tech billionaire-style with headset mic so he can roam the stage expansively. In one he leaps onto a chunky cubic metre of timber and tells the audience excitedly that it safely stores a tonne of atmospheric CO2, preventing it adding to climate change.
Among MGA’s projects are the Wood Innovation and Design Centre in Prince George, British Columbia (BC), formerly, at 29.5m, the world’s tallest modern, all-wood structure. It also designed the 220,000ft2 T3 office block in Minneapolis. It was billed as the “first modern timber building in the US” and, when completed in 2016, was the largest in North America. MGA is now aiming higher still. Its entry for the Réinventer Paris urban regeneration architectural competition was Baobab, a large-scale commercial and residential complex, featuring a 35m timber tower.
In 2018 MGA became part of US$3bn Silicon Valley tech and construction group, Kattera. The latter has built a 250,000ft2 plant to make cross-laminated timber (CLT) in Spokane, Washington. Its goal is an integrated materials manufacturing-to-design-and-build model that will “disrupt” the construction industry. Mr Green said joining Kattera would increase the impact of MGA in the North American market and beyond and “advance our agenda on design, quality, sustainability and affordability”.
In his view, the advent of new generation mass/ engineered wood products, including CLT, laminated veneer and strand lumber and glulam, represents the first major development in structural building materials in 150 years. It gives architects the “first legitimate reason to revisit what the future of building looks like” in the modern era and can revolutionise construction globally as much as steel and concrete did.
“In North America we have a long-established culture of wood construction, but this has been in lightweight timber frame, which is only really suited to small- to medium-scale residential building,” he said. “Mass timber represents a major shift. These large-format panels and beams perform so much better in fire and structurally than lightweight timber frame and enable us to build bigger and taller with wood. Not only that, they match or better steel and concrete in many areas of technical performance, such as strength to weight, and in uniformity and predictability, so they can be better understood and assimilated in building cultures where these are the default structural materials.”
Mr Green lists engineered wood’s multiple benefits; it lends itself to building prefabrication, it’s quick to build with, it’s low waste and low weight, which means fewer gas guzzling building component deliveries to site and less massive, intrusive foundations. Critically it also has a significantly lower environmental footprint. In short, he says, engineered timber is the material for building in urban centres at a time when urbanisation and urban construction densification are accelerating worldwide.
“Wood is the ultimate in rapid renewable building materials; renewable on a 50-year growth cycle, and even less in the case of fast-growing tropical species. It’s got the lowest water and lowest carbon footprints – trees actually sequester CO2 from the atmosphere as they grow. It’s low energy to process and transport, delivers inherently energy efficient buildings and it doesn’t require hauling non-renewable resources out of the ground, like concrete, steel and the fossil fuels you need to make and process them,” he said. “So, as urbanisation accelerates, wood is finding this new form ideally suited to urban environments, with new products and approaches that are easier for other building cultures to comprehend.”
The environmental impact of building materials, he added, is becoming an ever more important consideration, further stacking the arguments in favour of wood.
“As we become better at improving the energy performance of buildings in-use, through renewable energy technology and insulation, the carbon and wider environmental performance of our building materials themselves are set to become ever more significant factors in the overall impact of the structure,” said Mr Green.
“It may be a big statement, but the only way to build a high embodied carbon building is with wood. Some other materials, notably aluminium, have horrendous carbon footprints. We have this construction soup we’re making and the only ingredient you can throw in flat out and come out carbon neutral is timber.”
Modern mass timber building has its origins in central Europe and has grown most rapidly there, in North America and other developed regions using softwoods and, to a lesser extent temperate hardwoods. But Mr Green sees its greatest possibilities and potential economic and environmental impacts coming in developing countries, including in the tropics.
“My personal interest is in how this whole movement in construction can ultimately address the needs of the developing world,” he said. “In South America and Africa, for instance, there are great opportunities. In both regions, urbanisation is happening much faster than Europe and North America. At the same time the rate of deforestation is among the highest in the world, with the loss of habitat and carbon emissions that causes.
“But they have these fast-growing species, such as bluegum and eucalyptus, which are renewable on a 10-12 year cycle, with all parts of the tree being usable, and which could be ideal for making modern engineered wood products like laminated veneer and strand lumber. Currently they don’t have the technical capabilities to manufacture and use these materials at scale in these regions, so they’re building more and more in old school, unhealthy ways to cope with urbanisation. But industries elsewhere, where this form of building is established, could help develop their capacity.”
This in turn could be part of the solution to halting, even reversing deforestation.
“Environmental certification schemes have advanced sustainable forest management to a degree in tropical regions, but alone they’ve struggled to create a commercially sound argument for not taking the immediate financial return of a deforestation and redevelopment programme,” said Mr Green.
“Currently there’s a stronger economic argument for these countries to convert their trees to timber for immediate financial benefit, then switch the deforested land to more profitable agriculture, soya or palm oil plantations or construction. These new higher added value engineered timber products could provide the financial incentive to adopt sustainable forest management and even reforest deforested areas, as well as the route to the lower carbon, energy-efficient building approaches so urgently needed.”
What could also give added impetus to wood building in the developing world, he said, is a change in mindset on the value of fast-growing timber plantations.
“I certainly don’t want to see the destruction of old growth, natural forest to accommodate plantations. But properly located, managed well, with the right rotation and restoration of soil nutrients, they can be beneficial, both in terms of reducing the need to clear natural forest and in providing the huge volumes of timber needed.”
To achieve this shift in attitude and assist the spread of wood construction internationally, Mr Green also advocates greater accord and co-operation between the timber and timber building industries, environmental certification schemes and green NGOs.
“There is already a growing appreciation that they have shared values. The timber industry is recognising that environmental groups can be valuable partners and environmental groups that the industry has an economic interest and commitment to managing forest sustainably. But there’s still room for improvement,” he said.
“In particular we need to move on from the view that one size fits all when it comes to environmental certification. There should be more adaptation to regional and local environments, conditions and needs, and to develop the understanding for this in turn requires greater investment in forest science and forest schools worldwide.”
Mr Green believes too that greater credit for building with wood should be given by the green building schemes, such as LEED in North America and UK-based BREEAM, which “formed their mindsets at a time when chopping down any trees was considered bad”.
Government attitudes need to change further too.
“Many countries have now changed their construction codes to allow taller wood building,” said Mr Green. “And I’m not an unquestioning advocate of building ever higher, as we don’t understand widely enough how to do this without adverse social and cultural impacts and building sustainably also means building successful communities. However, I don’t think we should arbitrarily set limits on numbers of storeys in wood buildings. That should be dictated by our engineering capability and ingenuity.”
While there are challenges ahead, however, Mr Green is confident the case for building in wood is set to become ever more convincing.
“I don’t think there’s any possibility of this movement to timber reversing,” he said. “We still need to build momentum, but we’ve crested the hill and that’s to the benefit of societies globally, the forest and the planet.”
