Surrounded by giant slabs of cross-laminated timber
September 26, 2020 12:12 AM Subscribe
Austrian Wood Providing Answer to World's Concrete Problem - "For Austrian timber merchants, who cover about half the world's CLT demand, the material is a bridge linking the digital age to three centuries of forest management begun by Hapsburg Empress Maria Theresia. She saw Austria's forests as a national-security resource and mandated strict sustainability laws."
CLT uses a high-tech manufacturing process that turns ordinary wooden planks, often made from the nearby Spruce trees, into structures that can bear thousands of tons of weight. Architects from Australia to Scandinavia and the U.S. have been buying from Huter as they leapfrog each other in a race to construct the world’s tallest wooden skyscraper. Vienna made an entire new city quarter out of CLT. Designers in Japan have planned a 350-meter (1,148-foot) tower.What 'net-zero carbon' really means for cities - "The built environment is responsible for around 40% of the UK's total carbon footprint, according to the UK Green Building Council – and is another aspect of the city that needs to be rethought to achieve net-zero status."
Huter pointed to a project at 55 Southbank Boulevard in Melbourne, Australia which used his timber to add 10 stories onto a six-floor building, more than doubling its height and living space in less than a year. Because wood weighs just 30% of concrete, CLT is being used to expand scarce space in cities by building higher. Construction time is quicker than pouring concrete on site, resulting in lower labor and equipment costs.
Builders emit more than a fifth of the greenhouse-gas emissions spewed into the Earth’s atmosphere every year and convincing them to adopt greener materials -- which include hemp and even straw -- will be key to keeping global temperature increases well below the 2-degrees-Celsius (3.6 degrees Fahrenheit) mark mandated by the Paris climate accord. But it’s not just CLT’s potential to rapidly put the brakes on emissions that’s behind demand.
Using timber “significantly reduced” construction time, according to Bates Smart, the architectural firm that designed 55 Southbank. Wood in the structure sequestered some 4,200 tons of carbon dioxide, equal to the annual emissions of 130 homes.
Analysing the amount of carbon emitted per cubic metre of each material, the project demonstrated that glass and steel were among the materials with the highest carbon impact, while more sustainable, low-carbon options include brick, stone and cross-laminated timber (CLT) – especially if they are locally sourced. Steel, for instance – which is often used for building skyscrapers – is responsible for at least 7% of global CO2 emissions, releasing 12.2 tonnes of CO2 per cubic metre used, in part due to the heating process involved in making it. Concrete produces 550kg (1,200lb) CO2 per cubic metre used, but its main ingredient, cement, is responsible for about 8% of global CO2 emissions due to its widespread use as cities rapidly develop.
Timber has much lower embodied carbon, however, and CLT is actually a carbon negative material (sequestering more carbon than it emits). CLT is made from trees grown for around 40 years in a managed forest before being harvested, cut and pressed together with adhesive. The trees absorb and sequester carbon as they grow, so that CLT effectively absorbs 600kg (1,300lb) CO2 per cubic metre. CLT is also strong enough to be used structurally, with quick construction and reduced waste. (Read more about timber buildings as a solution to climate change)
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