by Benjamin Gillies
May 19, 2013
Original Source: thestar.com
In 1885, the Home Insurance Building in Chicago opened its doors. At 10 storeys, it was the world’s first skyscraper, and the first building to use a steel frame in its construction. Since then, the use of steel and concrete has proliferated, allowing North American architects to build taller and evermore impressive multi-storey structures.
While these two materials dominate modern high-rise construction, both come with serious environmental concerns. Three and 5 per cent of the world’s carbon emissions are generated in steel and concrete production, respectively. As such, a growing number of architects argue we must find a new material to meet building needs in the 21st century, and they believe they have the perfect alternative: wood.
Of course, wood is not a new product; humans have been using lumber in construction for thousands of years. Even in 2013, almost 80 per cent of Canadians live in wooden homes. Because of very legitimate concerns of rot and fire, however, back at the turn of the last century building codes restricted wood structures to no more than four storeys — and these regulations have remained on the books since.
Today though, the technology exists to build timber-framed high-rises stretching up to 30 storeys. Proponents point out such wooden skyscrapers would not only be cheaper than their steel and concrete counterparts, but sustainably forested timber is also far more environmentally friendly than conventional construction materials. According to Vancouver architect Michael Green, there is enough wood grown every 13 minutes on this continent to make a 20-floor building, and unlike producing steel or concrete, which emits greenhouse gases, using wood in construction actually sequesters carbon.
In fact, due to the effects of climate change and insect infestation, there is a growing population of dead trees in North America. Instead of leaving these to decompose and release carbon dioxide into the atmosphere, advocates argue this bountiful resource could easily be harvested, treated, and put to use building up cities.
In 2009, the first modern wood high-rise was built in London. The nine-storey condominium tower proved hugely popular, with all 29 units selling out within an hour. A seven-floor building then went up in Sweden, and Melbourne, Australia, currently boasts the world’s tallest modern wood building, a 10-storey skyscraper. The apartment block will soon be eclipsed, though, as Vancouver is reviewing a proposal for a 16- to 20-floor wooden tower, and Sweden has already approved a skyscraper of 30 storeys.
Certainly, many people may be skeptical of the feasibility of wooden cities, fearing the lumber will easily catch fire. Yet, as Geoff Triggs, an expert with LMDG Building Code Consultants, points out, wood high-rise construction does not use small two-by-fours. Rather, super-compressed mass timber — engineered wood layered together with adhesives or fasteners — is used to make huge panels 64 feet long and 12 feet wide. The compressed lumber has proven to be as strong as concrete but much lighter, which improves a building’s structural integrity.
Most important, the compression process creates dense wood blocks that, much like a big fat tree stump in a fireplace, are very difficult to burn. When a fire does catch, it moves slowly and behaves predictably, allowing for uniform safety measures to be put in place. A 2012 study published by Surrey, B.C.’s fire chief noted that modern fire protection systems such as sprinklers (that did not exist when most regulations regarding wood building construction were adopted) “more than mitigate” the risks of building tall timber structures.
In the next 20 years, 3 billion people will be moving to cities around the world, and high-rises will be a critical part of their housing mix. According to wood advocates, modern safety measures and technology mean this ancient material can be an asset in building these new skyscrapers. The biggest hurdle will likely be convincing the public that wood is just as safe as conventional concrete and steel — but as more wooden buildings go up, engineers will be able to provide hard evidence as to whether or not they are more dangerous than conventional structures. It would be nice if they do prove to be secure; beyond the considerable environmental benefits, wood could add an appealing warmth to the skyline that is impossible to achieve with drab concrete and steel. If nothing else, it would give new meaning to the phrase “city of trees.”