Are wooden skyscrapers the future of tall buildings?
A new generation of timber-framed skyscrapers is being built and planned in cities around the world. Could they be the answer to our environmentally destructive and insatiable demand for concrete?
T
imber is not traditionally considered a futuristic building material. After all, humans have been using it for shelter since one of our ancestors built the first wooden lean-to.
But after decades of concrete, steel and chrome filling our skylines, timber is once again in vogue as an environmentally friendly and entirely renewable construction material that can satisfy our ever-growing demand for safe, tall, high-density housing and workspaces.
Timber’s resurgence is largely down to a relatively recent innovation: cross-laminated timber (CLT), which is made by gluing layers of solid wood together at right angles to form sturdy beams and panels with the structural rigidity and strength necessary for constructing tall buildings. Architects have been quick to explore this potential – and today the age of the wooden skyscraper is almost upon us.
Growth industry
Canada was an early adopter of CLT, and has led the world in its use. Until recently, the tallest timber-framed building in the world was the 18-storey Brock Commons Student Residence in Vancouver, which was completed in 2016.
Brock Commons didn’t hold the crown for long, however. In March this year, the Mjøstårnet building was completed in Norway using locally harvested timber. At 85 metres tall, Mjøstårnet is currently the world’s tallest timber-framed building, but already it is set to be dwarfed by a new generation of skyscrapers planned around the world, the tallest of which – Tokyo’s W350 Tower, expected to be completed by 2041 – will top out at 350 metres.
Concrete evidence
There’s no doubt timber is on the rise, both literally and figuratively. But how feasible is it as a long-term replacement for concrete – the most widely-used man-made material in existence? In 2017, the world consumed more than 4 billion tonnes of the stuff, and our concrete addiction has caused enormous environmental harm. Concrete production is responsible for an estimated 8% of global CO2 emissions – and as well as its contribution to climate change, concrete production is making us more susceptible to climate change’s effects. Concrete is made largely of sand, and to meet our insatiable demand we are strip-mining beaches and riverbeds faster than they can be replenished (unfortunately, desert sand isn’t suitable for making concrete because its grains are too rounded). In a future in which storms, flooding and other extreme weather events are going to become more commonplace, that’s bad news, because beaches act as natural breakwaters for coastal communities.
Wooden it be nice?
Timber is more environmentally friendly on all counts. As well as being renewable, it acts as a carbon sink; the CO2 absorbed by the growing trees stays locked in the building from which they are made. Timber-framed building are around 40% lighter than their concrete and steel equivalents, too, which means less concrete is required for their foundations. Perhaps most surprisingly, skyscrapers built from timber are better at withstanding fires than than those built from steel, which melts at high temperatures. And CLT is easily prefabricated offsite – all of which can cut construction times in half. Brock Commons, for example, took just seven months to build, and was completed four months ahead of schedule.
Timber isn’t going to replace concrete anytime soon, however. At a very rough estimate, it would take something like 1.5 billion pine trees to produce an amount of building material equivalent to the concrete used globally in 2017 – and we really need to look after our forests. But it’s certainly going to be part of the solution. Timber skyscrapers will be sprucing up our cities in the near future; we just need to be able to see the wood for the trees.
The ideas presented in this article aim to inspire adaptation action – they are the views of the author and do not necessarily reflect those of the Global Center on Adaptation.
