Better building through design

Cambridge, U.K. — The construction industry, which uses half of the 1.5 billion tonnes of steel produced each year, could drastically reduce its carbon footprint by optimizing the design of new buildings to use less material, according to research from the University of Cambridge. Smart design could slash the sector’s carbon emissions by around 50 percent, without any impact on safety. If buildings are also maintained for their full design life and not replaced early, the sector's emissions could in total be cut by around 80 percent — the target set in the UK's 2008 Climate Change Act.

At present, in order to keep labor costs down, the construction industry regularly uses double the material required by safety codes. Analysis of more than 10,000 structural steel beams in 23 buildings from across the UK found that, on average, the beams were only carrying half the load they were designed for. The results were published in the June 4 issue of the journal Proceedings of the Royal Society A.

Over one-quarter of the steel produced each year is used in the construction of buildings. Demand for steel is increasing rapidly, especially in the developing world, and is expected to double in the coming decades.

The iron and steel industry contributes nearly 10 percent of total global carbon emissions, which climate change experts recommend be halved by 2050. Coupled with skyrocketing demand from the developing world, drastic action is required if a reduction in the sector’s carbon footprint is to be achieved.

One option to achieve this reduction is by designing and building more efficiently, delivering the same performance from buildings but with less steel, but this is not common practice at present.

“Structural engineers do not usually design optimized structures because it would take too much time; instead they use repetition to decrease the cost of construction,” said Dr Julian Allwood of the Department of Engineering, who led the research, which was funded by the UK’s Engineering and Physical Science Research Council (EPSRC). “This leads to the specification of larger steel components than are required.”

The researchers found that building designs are exceeding Eurocode Safety Standards by a factor of two and so are unnecessarily using double the amount of steel and concrete needed. “As materials are cheap and structural design time is expensive, it is currently cheaper to complete a design by using safe but considerably over-specified materials,” said Dr Allwood.

Additionally, many buildings are being designed to last for 100 years but on average are replaced after just 40.

By designing for minimum material rather than minimum cost, steel use in buildings could be drastically reduced, leading to an equivalent reduction in carbon emissions, at relatively low cost. The net result of avoiding over-design and early replacement is that the UK could provide the same amount of built space with just 20 percent of the materials — and therefore 20 percent of the carbon emissions — used at present.

“We need to see a more sensible use of materials in the construction sector if we are to meet carbon reduction targets, regardless of the energy mix used in manufacturing the materials,” said Dr Allwood.