Photo by Barthelemy de Mazenod on Unsplash

How to reduce the 11 per cent of emissions released while constructing a building and producing its materials will be front and centre at The Fifth Estate’s upcoming Building Circulatory event on 24 November (details coming soon). It’s a huge challenge that will involve architects, engineers, scientists, developers and, believe it or not, quantity surveyors.

Quantity surveyors know the cost of every screw and nail going into a building for the purpose of minimising the use of expensive materials. Now imagine if this same scrutiny was also applied to the embodied carbon content of each building material.

Recognising the unique position of quantity surveyors to simultaneously strip embodied carbon and cost from a building, last year researchers from UNSW, the CRC for Low Carbon Living and Multiplex set out to work out if embodied carbon could be inserted into the value engineering process.

“The quantity surveyor discipline is determining what goes into the building, they are the right ones to be considering the carbon efficiency of a building, we need to bring them to the front of the discussion,” UNSW associate professor in architecture Philip Oldfield told The Fifth Estate.

He says that there’s no real reason why value engineering decisions, which are based on all the different building components to determine the total cost, shouldn’t also be taking embodied carbon into account at the same time.

The goal, according to Oldfield, was to discover if structural tweaks could reduce both costs and embodied carbon without forcing architects to go back to the drawing board on their designs.  

The finding? Changes to the structure of the building can indeed cut both embodied carbon and costs simultaneously.

The research compared the cost and embodied carbon performance of a building with a simple concrete frame compared to four other similar building with different structural make up: a flat concrete slab structure, a post-tensioned concrete slab, a steel deck system and a mass timber structure.

Unsurprisingly, the mass timber option was the most carbon efficient system, seeing a 13 per cent drop in embodied carbon (or as much as 45 per cent if carbon sequestration is considered) and a 5 per cent reduction in capital costs.

The best preforming structure for cost was the flat slab, which slashed embodied carbon by 6 per cent and costs by 15 per cent.

From Carbon Value Engineering: Reducing carbon and cost in buildings by Philip Oldfield, Associate Professor in Architecture, UNSW and Mehdi Robati, Research Associate, UNSW

The report does, however, point out that different building compositions may impact on operational energy performance.  

While the total savings were modest, the researchers say that there’s value in optimisation and rationalisation of the design.

“Efficiency is sustainable. When we are able to use less materials in construction, we often see a triple-benefit of reduced embodied carbon, reduced cost and greater available floor area for rent – thus benefitting planet, profit and people,” the report states.

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  1. This is such old news – 80’s. But beware of throwing the baby out with the bathwater. Embodied Carbon is the 10-20% story – operational is the 80-90% story. If you focus on embodied but compromise operational, you’ll do all the wrong things. A lowest embodied energy building is one with no insulation, single glazed windows and no heating or cooling system, or a really simple inefficient one – it would have tungsten filament lamps not LED’s….etc. The only way to really do it right is with whole life-cycle tools like ENVEST, but its still just an unfunded prototype.