The construction industry requires the extraction of vast quantities of materials, resulting in the consumption of energy resources and the release of deleterious pollutant emissions to the biosphere. Energy and pollutant emissions, such as carbon dioxide (CO2), may be regarded as being 'embodied' or associated with materials. Here the embodied energy was viewed as the quantity of energy required to extract, process, and supply the material under consideration. Likewise the emission of energy-related pollutants, like CO2 that is a concern in the context of global warming and climate change, may be viewed over their life cycle. This gives rise to the notion of embodied carbon. With an estimated 7.6-10.8 million new dwellings to be constructed in the UK by the year 2050 (Palmer et al., 2006), the embodied impact of such construction must be considered.
The ICE database (Hammond and Jones, 2008a and 2008b) has been applied to both domestic and non-domestic buildings. Forty case study buildings were collected for domestic buildings (Hammond and Jones, 2007). These were primarily extracted from a variety of literature resource, including several primary case studies. These resources did not always contain sufficient detail on the building specification and therefore the ICE Domestic Building Model was created. The model operates in a bottom-up manner; therefore allowing buildings to be reconstructed through the selection of walls, floors, roofs, etc. Application of this model and comparison with the case study results allowed initial embodied energy and carbon benchmarks to be created for semi-detached, detached, terraced, bungalow (detached), and apartment (three storey block and four storey block) dwellings. Benchmarks were created for 'typical' English buildings of each classification. The average detached property was determined to have the highest embodied impact; however, they also had by far the largest floor area (125 m2). An average newly built (detached) bungalow was estimated to have a slightly lower impact but with a much reduced floor area (76 m2) they were determined to be an inefficient method of construction. Semi-detached buildings (73 m2) have significantly lower embodied impact and terraced buildings (68 m2) lowest yet. Apartments were determined to have the lowest impact, but only provided an average floor area of 50 m2.
Normalized results per unit floor area may appear particularly attractive to apply as benchmarks, they are simple to apply and easy to understand. However, it must be noted that the relationship of embodied carbon to floor area is not linear, and therefore buildings of different sizes (but same type) normalize to give very different results. Normalized results of embodied energy and carbon may be particularly unsuitable for environmental policy making and legislation. Analysis suggested that larger properties experience lower embodied carbon per unit floor area. Therefore if regulation required all semi-detached buildings (for example) to have an embodied carbon below a specified threshold (per unit floor area) the easiest way to achieve this would be to increase its total floor area. This would, however, increase the total embodied carbon of the property. In light of this it was recommended that any environmental policy or legislation should set absolute benchmarks of embodied energy and carbon (such as Fig. 23.5, Fig 23.6, or Table 23.2) rather than normalized benchmarks (such as Table 23.3). Such regulation would allow society to reduce the total (embodied plus operational) energy and carbon impact of residential construction, thereby minimizing 'concealed' impacts.
The research leading to the development of the ICE inventory was principally supported via a UK research grant awarded by the Carbon Trust and the Engineering and Physical Sciences Research Council (EPSRC) [Grant GR/S94292/01, as part of the 'Carbon Vision Buildings' (Building Market Transformation (BMT)) Programme] awarded to the first author (GPH). Both authors are grateful to the BMT consortia coordinators: Dr Brenda Boardman and Dr Mark Hinnells of the Environmental Change Institute, University of Oxford. Dr Boardman was succeeded in her post by Dr Nick Eyre on October 1, 2007. The corresponding author (CIJ) is at present partially funded via a strategic partnership between E.ON UK (the electricity generator) and the EPSRC to study the role of electricity within the context of 'Transition Pathways to a Low Carbon Economy' [under Grant EP/F022832/1]. Here the ICE database is being used to aid the determination of the embodied energy and carbon associated with various types of power generation plant. Prof. Hammond is the co-leader of this large consortium of university partners (jointly with Prof. Peter Pearson, an energy economist from Imperial College London). The authors greatly appreciate the interchange with Peter Pearson and the other main UK partners at E.ON Engineering and at the Universities of East Anglia (Prof. Jacquie Burgess), Leeds (Dr Timothy Foxon), Loughbor-ough (Dr Murray Thomson), Surrey (Prof. Matthew Leach), and Strathclyde (Dr Graham Ault and Prof. David Infield), as well as at Imperial College London (Prof. Goran Strbac) and Kings College London (Dr Neil Strachan). The authors have also benefit-ted from a discourse with colleagues in the Sustainable Energy Research Team (SERT) at Bath. However, the views expressed are those of the authors alone and should not necessarily be attributed to the collaborators or funding bodies.
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