Wood as strong as steel. Wood that engineers and architects have coined ”plywood on steroids,” constructed with a layering and gluing technique making it a lightweight super-strong material that replaces steel and concrete in building skyscrapers. It’s called cross-laminated timber (CLT). This isn’t the future—tall building have already been constructed with it where the floors, ceilings, stairwells, and elevator shafts are made entirely of this wood.
WWWAlthough it’s improbable that mega-skyscrapers will be built with CLT, there are plans to build structures as high as 40 stories, leaving plenty of opportunity for CLT to be a major player in building construction since the largest cities in the world have only a few skyscrapers taller than 40 stories. A nine story CLT building now sits in East London called Stadthaus, with a seven-story CLT apartment tower near it, and in Melbourne there’s a ten-story apartment building called Forté. In Prince George, British Columbia they’re building a 90 foot tall wood building, in Stockholm, Sweden they’ve approved a 34-story tower, and after the 2009 earthquake in Italy, 4,000 homes were rebuilt with cross-laminated timber—northern Italy manufactures the equipment to produce CLT.
WWWWood is strong in the direction of the grain, yet weak in the perpendicular direction of the grain. CLT takes advantage of the grain strength by layering wood in perpendicular layers relative to its grain, infusing the panels with superior strength in either direction.
Not only does CLT have colossal strength, it’s also more fire resistant than steel because fire chars the wood on the outside sealing the wood, whereas steel actually begin to melt usurping all its strength. Steel is only used to affix the vertical and horizontal panels with L-brackets, and the horizontal lengths between the vertical support panels are substantially longer than those employed with steel or concrete beams without compromising weight-bearing strength. Also, panels are custom made where windows and even piping and electrical wiring are preinstalled, enabling workers to simply screw them together, making it 15 % cheaper than concrete and steel and easier to construct. Panels can be made up to twelve inches thick. In Japan, a seven-story CLT building was tested on a shake table, surviving over fourteen different earthquake scenarios with only minimal damage.
WWWThe nine-story Stadthaus building in London took four workers only 27 days working three days a week to construct the CLT portion of the structure, which is about 30% faster than using steel and concrete. With modern technology, architects design a building using 3-D AutoCAD software, where it creates the specs for the material and communicates them to robotic wood routers, forming the modules with millimeter precision.
From an anti-carbon producing perspective, wood is the perfect product. According to Popular Science magazine, the main impetus for architects and developers favoring wood structures is climate change. Wood is a carbon black hole, absorbing carbon dioxide from the air and capturing it. Cut down timber still retains the carbon, making it a light-year more environmentally friendly than steel and concrete. It’s estimated that the Stadthaus building stores an unbelievable 186 tons of carbon, whereas steel and concrete would have produced 137 tons of carbon dioxide for the same structure—an incredible 323 ton differential—that’s 323 tons less carbon in the atmosphere.
WWWBoth steel and concrete are far greater generators of carbon than wood, because of the immense amounts of energy used to manufacture them, producing over a ton of carbon dioxide per ton of steel or concrete. It seems, environmentally, wood is king—a ton of concrete needs five times the energy than does a ton of wood, steel 24 times the energy, bricks four times, and aluminum uses 126 times. And CLT has five times the insulating effectiveness than concrete, and a whopping 350 times more insulation effective than steel.
WWWMy first thought would be that it would mean cutting down great numbers of trees which absorb carbon dioxide from the atmosphere to produce CLT, and therefore will be severely damaging to the environment. Ironically though, the Mountain pine beetle has ravaged millions of acres of North American forests, and if these trees are not removed, they will rot, emitting untold tons of carbon into the atmosphere. So, it seems that CLT and the devastation of these tress have converged into a timely environmental friendly marriage, but, since there’s only a handful of CLT factories worldwide at this moment, the prospect of getting to all of the trees before they rot is grim, but its a new process that will certainly move us in the right direction environmentally.
WWWThe future of cross-laminated timber technology looks very bright. A winning one at that, for the people, and the planet.