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Making building materials greener

04/09/2011

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Life-cycle assessment reveals potential for eco-innovation and substitution of traditional materials by natural, local equivalents to cut the environmental footprint of buildings.

The impact of a building on its environment has just as much to do with the materials used to construct it as with the demands it subsequently makes on resources such as energy and water during its lifetime. Indeed the former also impacts the latter!

To understand which materials are optimal from an environmental point of view, researchers at the Centre of Research for Energy Resources and Consumption (CIRCE) at the University of Zaragoza in Spain compared the impacts of a range of building materials across their lifetimes – from extraction through use to recycling or disposal. The work was carried out under the EU Seventh Framework Programme funded LoRe-LCA project, which coordinates efforts to apply life-cycle assessments (LCAs) to the European construction sector.

The CIRCE LCA was based on three parameters: primary energy demand, impact on global warming and water demand. Impacts were assessed per kg, although such a weight-based comparison has its limits since different weights of different materials may be able to fulfil the same function.

Results suggested natural, locally-sourced materials can be superior to conventional choices. For example, bricks containing local clays and renewable components such as straw had a lower environmental impact than traditional bricks. Replacing synthetic insulation materials such as polyurethane rigid foam with cork, wood fibre or sheep’s wool had a similar effect. Sheep’s wool has virtually no associated CO2 emissions, while polyurethane requires substantial amounts of energy and water.

As well as innovating in terms of material choice, the research highlighted the potential for eco-innovation in producing traditional materials. The footprint of cement, for example, could be improved by changing the production process for clinker, its main component. Switching to renewable energies and improving technologies to operate furnaces at lower temperature or make better use of waste heat could halve CO2 emissions from cement manufacture by 2050.

A third innovation avenue relates to better reuse of materials at the end of their traditional lifespan. Companies should be encouraged to construct buildings that can be disassembled rather than demolished. This would make it easier to reuse materials such as steel, aluminium, copper, glass and plastics. Producing secondary steel emits three-quarters less CO2 than the same amount of primary steel. Simple innovations would make buildings easy to take apart: using bolts instead of adhesives to hold materials together for example.

The final recommendation is for companies to use standardised labels, so- called Environmental Product Declarations, to communicate the environmental impact of each of their products. Information enables choice.

More information

Related information on the EcoAP Website