Costs of timber versus concrete
Using engineered timber instead of concrete and steel on commercial buildings may not be a lot more expensive, big construction firm Naylor Love says.
The company, New Zealand’s largest private construction firm with 700 staff and $600 million turnover, has developed a calculator that quantifies the amount of carbon in building structures using different materials.
The calculator is based on a report commissioned by Naylor Love and authored by sustainability experts thinkstep-anz. The research project modelled a typical six-storey commercial building constructed two ways – engineered timber versus conventional concrete and steel.
The engineered timber model reduced carbon emissions by up to 90 per cent, Naylor Love said. Engineered timber is large prefabricated components of solid wood glued together with high strength glues.
The Green Building Council says the built environment is responsible for about 20 per cent of New Zealand’s carbon emissions. About half of that comes from the operation of buildings through the use of electricity and fossil fuels for heating, lighting and ventilation, and the rest from ‘‘embodied carbon’’ emitted during the manufacture and construction of a building and its materials.
Naylor Love business development director Scott Watson said clients wanted to be more sustainable and needed the facts and figures that provided the rationale for their decisions.
‘‘The goal is to provide data that quickly demonstrates carbon benefits of engineered wood over alternative materials, alongside a cost-benefit analysis.’’
Wood was essential in moving New Zealand to a carbon-neutral economy. It was sustainable, renewable and less energyintensive to process compared to other construction materials.
‘‘The net total cost difference for an engineered timber structure can be as low as a few per cent of the total building cost.
‘‘For this, you can achieve about a 90 per cent reduction in carbon emissions.’’
Watson said the cost of engineered timber for the structure of a commercial building might be 3 per cent to 4 per cent more expensive than using steel and concrete for the structure.
But if the cost of carbon credits rose, the financial case for using engineered timber would improve even more.
The future cost of carbon credits depended on Government regulations and legislation to achieve its net zero carbon goals by 2050.
He was picking that using engineered timber would be costneutral with steel and concrete in the future.
The company had used engineered wood on large building projects, such as the Otago Polytechnic Student Village.
The tool could identify where the benefits were in using engineered timber in the structure. It did not measure the carbon in fitouts and interior materials.
‘‘We are not anti-concrete or anti-steel – those materials will always have a place in construction. You wouldn’t build a dam or motorway bridge out of timber, for example. But for some applications, the environmental benefits of wood can’t be ignored.’’
He was showing their research report to many large property companies for whom it was important to be seen to play their part in reducing New Zealand’s carbon emissions.
Naylor Love’s study has been reviewed and endorsed by Dr Andy Buchanan of PTL Structural Consultants, Emeritus Professor of Timber Design at the University of Canterbury, one of the pioneers of modern timber construction.