3.2.1 How to start and proceed with an LCA study

The first step, for both building and product LCAs, is to define the goal and scope of the study. This will determine the type of study that is required, and identify the relevant aspects that need to be considered. The decision tree shown in Figure 8 can help identify the type of study required for a given application.

The scope definition process will identify those life cycle stages that should be assessed, and those that will remain optional. It will also specify the data quality requirements and calculation rules (e.g. default values for screening LCA). Refer to Table 5 for identification of the mandatory and optional aspects (contributors and life cycle stages).

On the basis of the study type chosen and the life cycle stages of concern, the remaining relevant aspects are then taken into account during the set-up of the LCA building model, and when defining individual parameters of the system.

Figure 8: Decision tree to identify relevant aspects for a study

As the term ‘energy efficiency’ implies a lower energy input into a building or building service through a more advantageous benefit/input ratio, a comparison of the situation with or without the technology concerned may be required to identify the actual environmental consequences of utilizing such a technology. Careful definition of the two situations and a comprehensive life cycle view (inclusion of all relevant life cycle stages) are necessary to cover all the environmental consequences. Also, the comparison should be made on the basis of a common functional equivalent (i.e. a representation of the required technical characteristics and functionalities of the building or product).

3     How to use this guidance document

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