Of course, the wood comes from sustainable sources, usually from young plantation trees whose carbon is retained in the cellular structure of the wood.
In partnership with Dexus, Atlassian is planning a 39-storey hybrid timber office tower adjacent to Sydney Central Station, as part of the district’s Tech Central redevelopment, supported by the NSW government.
The project will target 50% less embodied carbon and 50% less energy consumption, and will run on 100% renewable electricity.
The project is touted as the largest hybrid timber building in the world – but maybe not for long. Further west, Grange Developments is applying for permission to build a 183m high residential hybrid timber tower in Charles Street, South Perth.
Not to be outdone, Milligan Group is in the early planning stages of a 220m structure in Sydney’s CBD on the corner of Hunter and Pitt streets.
Meanwhile, Perth’s first-ever hybrid tower, the 11-storey Westralia Tower II on St Georges Terrace, is under construction.
Wooden buildings can seem a bit medieval and an outdated material for skyscrapers. But, in reality, timbers are highly technical products such as cross-laminated timber (CLT) and glue-laminated timber (GLT), which have the strength to be used as structural elements in towers.
Known as “jumbo plywood”, CLT consists of layers of wood (slats) glued together, the grain patterns alternating to imbue the same strength as precast concrete panels.
The largest supplier of CLT in Australia and New Zealand by volume, XLam has led the adoption of solid timber in the high rise and conventional sectors.
“We work with the supply chain for green solutions. For example, Built works closely with [building material providers] Boral and Holcim will use cement-reduced concrete mixes.
— Joe Karten, Built Sustainability and Social Impact Manager
“The strong interest in wood is driven by a push towards greater sustainability in construction, as well as interest in construction products and methodologies that improve safety and efficiency,” says Jacqui Bates, manager technical at XLam.
She says that at 20% of the density of concrete, wood offers significant weight reduction advantages over traditional materials.
“This saves money on other structural elements such as slabs and frames, allowing applications such as vertical extensions on existing buildings and larger amounts of material on softer soils.”
Davina Rooney, chief executive of the Green Building Council of Australia (GBCA), notes that the initial carbon represents 16% of the country’s total building emissions. But as the power grid decarbonizes, that figure will jump to 85% if nothing is done.
“These are the hard emissions to reduce, which means we need to focus even more on what we build our buildings with,” she says.
“In this context, it is exciting to see the development of net zero scale buildings. These projects allow us to capture the full carbon impact of a building, including initial emissions or embodied carbon. »
According to the Built construction group, the use of such “mass” wood can reduce embodied carbon by up to 80%.
Built’s sustainability and social impact manager, Joe Karten, said while wood will play a key role in reducing embodied carbon, the solution requires a multi-pronged approach.
“We work with the supply chain for green solutions,” he says. “For example, Built has worked closely with [building material providers] Boral and Holcim use cement-reduced concrete mixes.
“Another option is to use ‘green’ steel made primarily from scrap metal and renewable energy in electric arc furnaces, rather than energy-intensive blast furnaces.”
An age-old answer is to renovate and rehabilitate old buildings, rather than demolish them and start all over again.
Built has worked on a number of building renovation projects that have retained original structures while introducing modern workplaces.
In the case of 20 Martin Place, Sydney, the office tower was reduced to 5,500 tonnes of bare steel structure, resulting in 40% less embodied carbon compared to a “knock down” rebuild.
Sydney MPA’s Quay Quarter Tower has also been redeveloped using the same principles.
At No. 164 Clarence Street Substation in Sydney’s CBD, an ‘adaptive reuse’ of two heritage buildings saw the adoption of a pre-loved form of steel, brick and timber in the lower part of the building, with a new extension above. This reduced the embodied carbon by 21% compared to a completely new structure.
GBCA’s Rooney says large-scale projects will ultimately lead to market transformation for the rest of the sector and the wider community.
“Ultimately, this will change the nature of the concrete that Bunnings sells to moms and dads.”