The sun-grown skyscraper
Will future generations stare up at wooden skyscrapers? Eoin Redahan spoke to Michael Green, the Canadian architect who is looking to grow these buildings.
We love the quick fix. We love the miracles of Lourdes, pocket book aphorisms and lottery wins. We like simple solutions, and we like them now. Unfortunately, science isn’t particularly good at the sudden cure-all. Research tends to build on what has gone before – slowly and steadily, like droplet-formed stalagmites.
As a result of this, we grow to become suspicious of amazing discoveries and grandiose claims. Somewhere along the line, we become less convinced by flying car designs and schematics of human habitats on Mars. But what of giant wooden buildings? Will they drastically reduce our reliance on carbon-hungry concrete and steel or is it all just pie in the sky(scraper)?
Michael Green’s Vancouver and New York-based company MGA has pioneered the Finding the Forest Through the Trees (FFTT) construction process, which enables the manufacture of 30-storey wooden skyscrapers. Green underlines why wood is his material of choice. ‘What if man went about making a product that was grown by the sun, that was incredibly strong and lightweight, with properties so diverse that it could be used in all different ways, with the capacity to store CO2 for the life of the product and produce oxygen while being made? If you had a man-made material that did all of those things, it would be seen as the most fantastic material on Earth. Nature has provided that material for us. We just haven’t thought about it in those terms.’
In more clinical language, a 20-storey wooden building can sequester 4,500 tonnes of CO2, which is the same as taking 900 cars off the road for a year. So, how can these buildings be made, and will they be commercially competitive? The answer comes in the form of a mass timber panel.
The construction process
In his TED Talks presentation, Green likened the mass timber panel to Lego. As children, we made a lot of our masterpieces with four- and six-dot bricks. However, if we were lucky enough to own a 64-dot piece, the scale of what we could build grew. In essence, traditional 2x4 feet construction is beginning to shiver in the shadow of the 64x8 feet panel – the tree-bred Goliath that is changing the way architects and engineers approach wood construction. These panels make it bigger. These panels make it quicker. These panels are central to the FFTT construction process.
Green explains, ‘We build using conventional foundation systems, which tend to be a lot lighter than in conventional concrete or steel structures. We take the large mass timber panels and erect them vertically. The panels are set so that they extend up to six storeys tall as a single panel. These are then braced in place and connected to the other panels around the building’s central core (by the elevator core and stair core). Columns are put up around it in a frame and big slabs of timber panels are put in for the flooring system. In layman’s terms, instead of stacking floors on top of walls, we’re hanging floors between the walls.’
While the construction method and materials used are unconventional, there is nothing unusual about the transportation of the mass timber panels. They are carried on flatbed trucks and arrive pre-cut at their destinations. Green also claims that overall material costs are similar to those in conventional large structures. However, he says the FFTT process gains in other areas. ‘The labour cost of these buildings is considerably less than that for steel and concrete, where you have to tie and lay all the rebar. They are just a lot more labour intensive [than FFTT structures]. So, part of our savings come from the ease and simplicity of assembly.’
MGA favours the use of fast-growth tree species and, where possible, low-grade trees that would ordinarily be harvested for the pulp and paper industry. Ash, maple and birch are used in the laminated strand lumbers, with fast-growing species such as eucalyptus earmarked for future use.
Even diseased trees, such as the pine weevil-ravaged Canadian spruce, might be of use. Green explains, ‘In Canada and the UK, some soft woods have a huge problem with the white pine weevil, Pissodes strobi. It used to die off every winter but now, with climate change, it’s not cold enough for it to die off and it is devastating our forests. Trees that are standing and dead are either going to burn or they are going to rot, and all the carbon sequestration in that forest is going to be lost back into the atmosphere. We can take these trees – even though they are not the highest quality trees – and turn them into our building panels. So, trees that are damaged by climate change can actually become part of the carbon storage solution.’
Making the dream a reality
Of course, there are concerns surrounding wooden building construction, with fire protection chief among them. The wood is treated with fire retardants, but only where there is the gravest risk of flame spread, such as in elevator shafts. Green notes that wood may not be a suitable building material in places at extreme risk of fire or explosion, and in hospitals, where the porosity of wood might be a problem.
For all the benefits of large-scale wood construction, Green feels that champions are needed for the cause – prototype buildings to create what he describes as an Eiffel Tower moment. To help drive this momentum, Green and his colleagues have ensured that the FFTT process is free for all to use under the Creative Commons.
There are signs of a coming spring for large wooden buildings, with multi-storeyed efforts sprouting in different parts of the globe. Construction recently began on wooden residential tower for Canada’s University of British Columbia. Designed by Acton Ostry Architects, the Tall Wood Building will rise to 18 floors on completion in 2017. MGA has even more audacious plans – for the tallest timber-supported tower in the world, a 35-storey skyscraper that will form part of a six-tower development called Baobab in Paris.
London has never been a city to be behind a trend, and wooden construction is no exception. In 2009, a nine-storey residential building was built from cross-laminated timber in Murray Grove, by Andrew Waugh, an architect and friend of Green’s. A 10-storey development in Dalston Lane followed two years later, using 3,000m3 of timber, and plans for an 80-storey, 300m high timber building were recently proposed by researchers from the University of Cambridge Department of Architecture, UK, and architecture firms PLP and Smith and Wallwork.
Not that Green believes concrete and steel should be replaced as building materials. He doesn’t claim that the FFTT process is the construction industry’s panacea, penicillin, or Messianic figure that will ward off the evils of carbon-kind. ‘There is no simple formula,’ he says. ‘Wood is a great material but it’s not the right material in 100% of cases. The same goes for steel and concrete. They’re great materials, but my thesis is that we should use less of them and use each one where it works best.’