Wood replaces steel as Japan builders fight climate change

Built by engineering group Obayashi, the building is an example of how Japan's leading builders exploring wood as an alternative to steel and concrete -- two of the most carbon-intensive materials -- as nations look to cut greenhouse gas emissions.

Carbon dioxide emissions over the entire life span of the building, from producing the materials to tearing it down, will total about 60% as much as for a steel-frame building of a similar size, Obayashi says. After accounting for the amount of CO2 absorbed by trees used to make the lumber, that footprint shrinks to around a quarter, the company estimates.

Obayashi has developed a new laminate material that can resist fire for at least two hours -- a legal requirement for use in high-rises -- for the building's pillars and beams. It avoided welding or bolting joints together and used cross-laminated timber for the floors and walls. This in turn eliminated the need to cure concrete, which Obayashi hopes will cut down on the amount of labor necessary for future projects.

In the fiscal year that ended March 2021, 13.9% of Japan's public building starts were made of wood, according to government data. About 30% of low-rise buildings are made of wood.

But overall, wood accounted for hardly any construction starts for structures four stories or higher in 2020.

That is starting to change. Insurance group Tokio Marine Holdings announced this month that the new headquarters building will be made of wood or hybrid material. The building will be one of the world's biggest in terms of the amount of wood used, the company said. ...continue reading