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Sustainability - Harnessing all that hot air

New Concrete EngineeringGovernment proposals to reduce the energy consumption of new buildings will increase concrete construction, Anna Scothern believes.

Recognising that energy used in buildings accounts for around 50% of the UK's carbon dioxide emissions, the Office of the Deputy Prime Minister has invited views on the implementation of the Energy Performance of Buildings Directive and on a proposed shake up of the building regulations. Subject to consultation, the changes could be in force by 2005.

The government believes that improving the energy efficiency of buildings is critical to achieving the carbon emission reduction targets outlined in the Energy White Paper and the Energy Efficiency Action Plan. It will also contribute towards achieving more sustainable communities.

As the UK's largest construction client, the government is already encouraging improved environmental performance by specifying 'Excellent' on the BRE-developed BREEAM environmental rating system for all new public sector buildings, and 'Good' for refurbishments. From April, the Good rating, from the equivalent EcoHomes rating system, will be specified by the Housing Corporation for new social housing developments.

Both the BREEAM and EcoHomes systems have been recommended by the governmentsponsored Sustainable Buildings Task Force to be the basis of a new code for future planning. In future this could mean that all private commercial and housing developments will be subject to stringent energy performance criteria.

These are criteria that concrete will successfully meet. The thermal mass of a concrete building is much higher than most other forms of construction, enabling it to absorb and store more heat. All buildings, whether homes, offices, schools or hospitals, generate heat via people, electrical equipment, lighting and solar gain. Exposed concrete absorbs this heat. This means daytime temperatures can be reduced by 3infinityC to 4infinityC and the peaks in temperature are delayed by up to six hours.

Exposing the soffits of concrete floor slabs provides a 'passive' cooling system that absorbs heat during the day and releases it at night. For higher cooling requirements an 'active' concrete system can be used.

This involves ducting air or water via a closed system through a concrete slab. Compared to energy intensive air conditioning, active concrete systems offer up to 50% reduction in carbon dioxide emissions and a 20% reduction in initial building costs.

Further benefits of the thermal mass properties of concrete include eliminating the need to install suspended ceilings, which saves around 7% on construction costs. Significant improvement of the internal natural light and air quality, and a more aesthetically pleasing structure, are bonuses.

Concrete offers other benefits such as fire resistance to increase the material's environmental and sustainability credentials. It means there is no need for additional fire protective coverings as required for steel structures, and no need for additional treatment to prevent deterioration such as volatile organic compound based preservatives used for timber.

The same principles of using the thermal mass of concrete can be applied to both commercial projects - such as the recently opened Vodafone offices in Newbury - or to housing projects such as the applauded energy efficient housing BedZED project in London.

The government's proposals acknowledge how in the future the energy performance of buildings is set to become a key issue in their construction. The new energy criteria to which buildings will be subject will certainly favour high mass construction.

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