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At over 80 m tall and completed in March last year, the Mjøsa Tower in the Norwegian town of Brumunddal holds the title of the world’s tallest wooden building

Push begins to boost engineered wood use in mid-rise buildings – By Dave MacIntyre

New Zealand is about to gain significant traction on a programme to increase the use of engineered timbers, such as cross-laminated timber (CLT), in construction projects – an initiative that will not only enable architects and engineers to design tall, earthquake-safe, fire-safe and beautiful wood buildings, but have major environmental benefits too.

For over a year, the Ministry for Primary Industries (MPI) has been working with forestry, wood processing and property development company Red Stag Investments to deliver Mid-Rise Wood Construction, a four-year, $5 million Primary Growth Partnership (PGP) programme.

Its aim is to boost mid-rise building construction (between four and 12 storeys high) using New Zealand-engineered and panellised framing timber and prefabrication to deliver a range of regional, social, environmental and other benefits.

The programme aims to help deliver economic benefits of $155 million by 2023 and $330 million by 2036, driven by a 10% lift by 2023 in the wood construction industry’s market share across the multi-unit residential and non-residential market.

It has three interrelated projects:

• Project 1 – building two mid-rise wooden buildings, paid for by Red Stag, to act as showcases and reference sites, and inform case studies

• Project 2 – documenting and collating the designs, details, reports, lessons, costs and feasibility information from the two showcase buildings

• Project 3 – promoting information developed by the programme through electronic media, workshops and building site visits by architects, engineers, quantity surveyors, constructors, real estate agents, manufacturers, urban councils, developers and investors.

Project 3 will include assembling a collective of excellence – a pool of New Zealand professionals experienced in mid-rise wood building design and construction – to help share and grow knowledge and expertise within the broader industry.

The programme is expected to begin showing physical progress soon. It is close to receiving consent approval to begin a five-level apartment development at Clearwater Resort, Christchurch, as the first showpiece building. Completion will be in early 2021.

All costs for actually constructing the building will be covered by Red Stag and its development partners. Mid-Rise Wood Construction covers funding for additional costs generated by the programme – for example, design work in engineered wood, collating and sharing information, educational site visits and establishing the collective of excellence.

Cost-effective and sustainable

Red Stag Group chief executive officer Marty Verry says combining CLT, glulam and panellised framing timber is a cost-effective, fast, resilient and sustainable system for mid-rise construction that is fit for widespread adoption in New Zealand.

“Aside from its natural beauty, engineered timber provides a very strong, low-carbon and comparably low-cost alternative to steel and concrete. It’s easier to transport, relatively light, and has outstanding earthquake and fire resilience. The use of prefabrication can speed up construction by as much as 30% and reduce costs to help meet New Zealand’s acute need for more accommodation.”

Red Stag Group CEO Marty Verry

Mr Verry says the overriding driver for greater wood use is climate change. “Concrete and steel production emits between 10% and 13% of the world’s greenhouse gas emissions. Joint research by Scion and the Canterbury and Victoria universities compared the emissions from a standard six-storey building. It found that it takes two wooden buildings to sequester the CO2 emitted by a third building constructed in steel or concrete. This 2:1 ratio should be New Zealand’s target to achieve zero carbon for the structures of our buildings.”

The programme’s target estimates for CO2 sequestered by higher levels of engineered wood in construction are: 150,000 tonnes per annum in 2022/23, 180,000 tonnes in 2023/24, 216,000 tonnes in 2024/25 and 259,000 tonnes in 2025/26.

Overseas use

New Zealand lags behind other countries in recognising the value of engineered timbers for mid-rise construction compared to countries such as Austria, Germany and North America. We are a small user of wood in commercial and institutional construction and it is only growing at an estimated 1% per annum.

First introduced in the 1990s, CLT has shown rapid growth overseas. Recent examples in the United States include the seven-storey T3 building in Minneapolis, the eight-storey Carbon12 building in Portland, Oregon, and a six-storey dormitory at Rhode Island School of Design in Providence.

In Canada, Norway, Sweden, the United Kingdom and Australia, even taller wooden buildings are already in use. The Mjøsa Tower in Brumunddal, Norway, is the world’s tallest wood building at 85.4 m – only 7.6 m shorter than the Statue of Liberty – and Forte apartments in Melbourne is eleven storeys.

Recently, the New York Times ran an article entitled ‘Let’s Fill Our Cities with Taller, Wooden Buildings’ in which the authors argue for the use of more sustainably-harvested wood to build tall buildings. It said that the energy embodied in the materials for new buildings around the world – mostly steel and concrete – accounts for 11% of global carbon emissions. Typically, coal is used to heat these materials to temperatures over 1370 degrees C in the manufacturing process, with CO2 generated in the chemical process.

Wood, in contrast, is forged from sunlight, and trees sequester carbon dioxide. A study by scientists from Yale University and the University of Washington showed that expanding wood construction, while limiting global harvesting to no more than the annual growth, could produce a combination of emissions reduction and carbon sequestration equivalent to eliminating construction emissions altogether.

In New Zealand, however, uptake has been slower due to factors such as limited production capacity and little knowledge of engineered wood use and prefabrication in mid-rise building construction.

Wider understanding

Spreading the word through the New Zealand construction industry is therefore a key part of the PGP programme, with a goal to double demand for engineered and panellised wood products in New Zealand buildings, as well as developing domestic manufacturing capacity.

The details of Red Stag’s showcase buildings – including the designs, reports, lessons, costs and feasibility studies – will be made freely available, and site visits will be arranged to the showcase buildings for building and construction professionals, urban planners and property developers.

A pool of professionals experienced in mid-rise wooden design and construction will extend the knowledge and systems to the broader industry through free technical manuals, open days, conferences and supplier models.

Steve Penno, director of investment programmes at MPI, says the benefits from the Mid-Rise Wood Construction PGP programme will be felt beyond the co-investors. “Engineered timber provides the opportunity to add significant value to New Zealand-grown timber. It’s also a natural and sustainable resource.”

He says the associated flow-on benefits of increased demand will be felt across the entire supply chain. “As well as speeding up construction through offsite prefabrication to help meet New Zealand’s acute need for more accommodation, there will also be lower building lifecycle costs, fewer construction workplace injuries, and less construction building waste, less disruption to traffic, less noise and fewer carbon dioxide emissions.

“This will create new regional jobs and renewed investment in forestry, processing, manufacturing, construction and prefabrication. Achieving the programme’s goals will significantly advance New Zealand’s engineered timber industry.”

Red Stag itself is investing $35 million in a new CLT plant on the Waipa Mill site it runs in Rotorua. It will have 50,000 cu m annual production capacity.

Dave MacIntyre is an award-winning journalist who specialises in transport and infrastructure issues within New Zealand 

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