As timber buildings go up, emissions come down

Data from engineering consultancy Arup last year showed buildings typically emit 600 kg to 1000 kg of CO2 per square metre over a notional 60-year life span, with roughly half of that from embodied carbon and half from operational carbon.

“Developers know the pathway to net-zero in operations,” Rooney says.

“The elephant in the room is embodied carbon – the energy used for manufacture. This year, 5 Star crossed the threshold where buildings will use more energy from building than they will use operationally over the length of their lifecycle.”

Globally, 50 million square metres-worth of real estate is being designed that will reach completion in 2030, Arup says. Whatever carbon those buildings are built with now will be baked in for a long time.

Driven by climate crisis

The urgency of the global climate crisis is prompting authorities around the world to pass ever more stringent rules around building emissions – assets with higher baked-in carbon content due to their materials risk losing value and struggling to secure tenants.

That’s driving a pick-up in the use of timber, replacing or reducing carbon-intensive steel and concrete in building structures.

The council’s own figures – for timber buildings registered for Green Star status – tell part of that story. Between 2011 and 2018 just five timber buildings were registered under the scheme. That doubled, with six more in 2019 and 2020, and doubled again with 16 more in 2021, 2022 and 2023.

”Of all the timber buildings registered with the Green Building Council over history, we’ve done more than 50 per cent in the last three years,” Rooney says.

Last year’s period of white-hot materials inflation – when overall building costs rose nearly 13 per cent year-on-year – has not left timber more expensive relative to other materials and builders are keen to use it.

“Timber is as much on the table for building where it makes sense as it was before,” says Brett Mason, CEO of Built, the contractor behind software company Atlassian’s $1.4 billion timber-and-concrete hybrid office tower in Sydney.

“We’re looking at a lot of projects incorporating timber as part of the structural solution but incorporating green steel or green concrete and timber.”

That point is crucial. Lendlease, which has built 26 engineered timber buildings around the world, points out that 70 per cent of a building’s embodied carbon comes from the steel, concrete and aluminium used in foundations and facades – even of timber buildings – and coming up with lower-carbon versions of these materials is crucial.

“We can’t expect timber to single-handedly solve all the built environment’s decarbonisation challenges,” says Lendlease head of sustainability Ann Austin.

Built, which used its Atlassian know-how to develop with Liverpool City Council in Sydney’s west a timber hotel and adjoining office tower – is now seeking to change to build-to-rent residential, given weakness of the office market.

It is also building a timber tower at 42 Honeysuckle Drive in Newcastle for developer Doma, which will include a 5750-square-metre office component and 181-room Little National-branded hotel.

Timber more expensive

Timber-only structures have less carbon than hybrid taller ones, but can’t go as high or offer the density. The Clean Energy Finance Corporation, a federal government funding agency, calls the 25-metre “mid-rise” mark the “sweet spot” for timber buildings.

One of the highest all-timber buildings in the world is Norway’s Mjøstårnet, an 18-storey mixed-use building with apartments, a hotel, swimming pool, office space and a restaurant that rises 85.4 metres off the ground.

For all its benefits, timber is more expensive. Supply is increasing, however, and that will bring costs down. This year manufacturer Timberlink became Australia’s mass producer of engineered cross laminated timber when it opened a new 15,000-square-metre factory at Tarpeena in southeastern South Australia.

It is the third major player in Australia’s mass timber market after New Zealand-based XLam, which opened in Albury-Wodonga in 2017 and Heyfield, Victoria-based Australian Sustainable Hardwoods.

Melbourne-based Grange Development recently won approval to build a 50-storey apartment tower in South Perth that at 191.2 metres would be the world’s tallest hybrid timber tower.

To build the building – marketing won’t begin until mid-2024 at the earliest – will cost a $14.1 million, or 8 per cent, premium on the construction of a conventional equivalent, managing director James Dibble says.

But he says this was less than the original estimates.

“When we started the project, the industry was saying that it would be between 10 and 20 per cent in terms of cost premium, so we do consider 8 per cent as a major achievement,” Dibble says.