Friday, March 18, 2011

Reducing the environmental impact of building materials

A recent study has compared the environmental impact of a range of building materials. Energy consumption, carbon dioxide emissions and water demand can all be reduced by switching to renewable sources of energy, improving technologies and promoting eco-friendly alternative materials.

Construction accounts for 24 per cent of global raw materials removed from the earth. In addition, the extraction, processing, transport and installation of materials associated with construction consume large quantities of energy and water.

This study, partly conducted under the EU LoRe-LCA project1, used a life cycle assessment (LCA) approach to compare the environmental impact of producing 1kg of a variety of materials commonly used in construction, in addition to some more environmentally-friendly alternatives. Three main impacts were considered: the primary energy requirements (related to the production, use and disposal stages of a product), the impact on global warming (measured in kilograms CO2-Equivalents) and the water demand.

The results suggest that making roof tiles out of concrete is a better option than using either ceramic or fibre cement roof materials: although ceramic tiles are better than fibre cement roof tiles in that they save 60 per cent more primary energy, concrete tiles are better again in that they save 42 per cent primary energy compared with ceramic roof tiles. In addition, it is preferable to use quarry tiles instead of ceramic tiles in flooring: quarry tiles provide an 86 per cent saving in primary energy and a 66 per cent saving in emissions.

For bricks, local clays and renewable constituents, such as straw, had lower environmental impacts compared with conventional bricks. Replacing synthetic insulation materials, such as polyurethane rigid foam and EPS (expanded polystyrene), with natural insulation materials, such as cork, wood fibre and sheep's wool, also reduces environmental impact. For example, production of polyurethane places high demands on primary energy and water consumption, whilst sheep's wool emits 98 per cent less CO2, if the wool is incinerated at end-of-life.

The energy-intensive manufacture of clinker (the main component of cement) is a major contributor to the environmental impact of cement products used in buildings. Switching to renewable sources of energy and improving technologies by making better use of the waste heat from the furnace or reducing the furnace temperature, for example, could halve the emissions of CO2 from cement manufacture by 2050.

Constructing buildings with wooden structures would also lower the primary energy demand and could be almost carbon neutral, or even carbon negative if the wood was recycled and reused at the end-of-life. Other construction materials, such as steel, aluminium, copper, glass and PVC should be reused and recycled where possible to reduce the primary production of these materials. For example, producing secondary steel (e.g. using scrap steel) reduces emissions by 74 per cent, compared with producing the same amount of primary steel.

Companies should be encouraged to construct buildings that can be disassembled rather than demolished at end-of-life, to make it easier to separate materials for reuse and recycling. For example, bolts can be used instead of adhesives to fix joints between materials. Upgrading technologies (e.g. in kilns) and techniques (capturing and reusing heat) and using local resources where possible can also reduce environmental impacts. In addition, eco-innovation should be promoted by identifying environmentally friendly products with ecolabels.

1.     LoRe-LCA (Low Resource consumption buildings and constructions by use of LCA in design and decision making) was supported by the European Commission under the Seventh Framework Programme. See:

Source: Bribián, I. Z, Capilla, A.V., Usón, A.A. (2011) Life cycle assessment of building materials: Comparative analysis of energy and environmental impacts and evaluation of the eco-efficiency improvement potential. Building and Environment. 46: 1133-1140./p> 

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