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Embodied energy calculations design toolSeptember 2009

BSRIA has published the Inventory of Carbon and Energy to help choose the ideal materials for low embodied carbon buildings.

As buildings become more energy efficient, carbon reduction strategies must focus more on embodied energy. Fiona Lowrie looks at a new design tool that might make the embodied energy calculations easier.

Spurred on by legislation, the construction sector has made great strides in delivering buildings that are designed to emit less carbon dioxide during their operation.

An extract from the data for embodied energy and embodied carbon for various forms of aluminium.

However, with a target of 80 per cent reduction in carbon being brandished by the UK Government, attention is now being focused on the total environmental penalties of buildings. This means counting everything, from cradle to grave.

The processing and end-of-life/recycling costs of constituent construction materials can contribute significantly towards a building's total environmental penalty. So it's important to establish a way of incorporating these factors into the selection process for construction materials, along with functionality and financial cost.

It is also essential that tools are developed that can support decisions on materials selection during the design and construction stages. However, there is a limited choice of such tools, in part due to limited access of freely available, good quality data.

To address this need the Sustainable Energy and Research Team (SERT) at Bath University has developed a new design database - the Inventory of Carbon and Energy - that will enable detailed predictions of the carbon content of a building to be made at any stage of the design process. BSRIA is working with the University to turn the database into a tool that can be easily picked up and applied by designers and constructors.

Development of the Inventory of Carbon and Energy (ICE) into a tool will occur in two main phases. The first phase is the compilation of a database that contains the relevant material data. Craig Jones and Professor Geoff Hammond at SERT have established a database that contains over 1700 records of embodied carbon and energy content of materials used in construction. The materials included could be used for both structural and aesthetic purposes, such as girders or carpets, and also for individual components, such as window frames.

The embodied energy scatter-graph for aluminium, which shows a range of +/- 20 per cent in the source data. Such transparency in the data reduces the risk of begged questions. SERT will be able to narrow the data band when more accurate information becomes available.

These data were collected from a range of secondary resources in the public domain and have been condensed into coefficients that can be used in the design process. The coefficients are presented in material profiles, as shown in Figure 1. (The database is freely available at the SET website).

The second phase in the ICE project is the integration of coefficient values from the database into some form of design tool that could be used throughout the design process. The level of complexity in such a tool will vary with each user, with output format ranging from basic calculated values to advanced data lists and graphical displays. In all cases the tool should enable rapid predictions of costs, so that comparisons of the environmental effects of various materials can be made and this information included in the decision process for material selection.

Ideally, the environmental predictions would be incorporated as a separate module into a wider package that could allow additional parameters to be added at a later stage. Such a tool should be of direct interest to both designers and assessors. BSRIA hopes to form a network of industrial partners to develop such a module over the coming months.

The future of the database

The potential of this tool is far-reaching. While the initial focus has been on embodied carbon and energy values there is no reason why other data could not also be included at a later stage, such as service life, water use, regulation and waste/recycling. In addition it could be extended from predicting the environmental consequences of individual components and building to multiple building zones (such as a campus).

Although there is little incentive, apart from public criticism, for companies to consider the environmental costs of demolishing and constructing buildings, this is bound to change. BSRIA believes that when environmental costs are finally converted into financial penalties, through legislation for example, then companies that have established a way of selecting materials with reduced environmental effects could enjoy commercial advantage in the construction sector.

Fiona Lowrie PhD CEng MCIOB is a principal research engineer within BSRIA's Microclimate and Test Group.


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