How can the practitioner set up the goal of the study? Are there special cases where the effort of goal definition can be simplified in regard to product or building LCAs?

The documentation should also be in line with ISO 14044, EN 15978 and EN 15804.

Guidance for specific aspects of the goal definition are given in the other EeBGuide aspects ‘Comparative assertions’, ‘Classifying the decision context as situation A, B and C for building and product LCA’ and ‘Future technical development and innovation’.

The goal of the study needs to be defined at the beginning of the study and should – with regard to the relations mentioned below – clearly state the objective of the study. Typically, a study cannot adequately address several different goals, but should address one single goal. If several goals are pursued when conducting LCA studies, e.g. within one research project, separate studies – possibly based on a common basic product model – should be conducted.

1) General guidance: need for flexibility versus strictness

The goal definition applied in the building sector should be handled with care, as many different uses of LCA can be found. This general guidance follows ILCD ‘Provisions 5.4: Need for flexibility versus strictness’.

On the one hand, when the purpose of the study is to make an EPD or to produce a building LCA for certification purposes, there is a need to ensure that consistent rules are applied. This is called ‘strictness’ by the ILCD Handbook. These goal definitions are likely to be related to situation A (i.e. attributional LCA; see the corresponding aspect ‘Classifying the decision context as situation A, B and C for building and product LCA’). In this context, the goal is typically predefined (e.g. ‘to conduct a building LCA for certification purposes’); however, for a research-project-related building LCA, for instance, the goal will have to be defined directly by the LCA practitioner.

On the other hand, when the purpose is to perform comparative assertions of policy options, e.g. for the different future grid mix options due to the use of renewables, there is a need for flexibility. In this example, several scenarios can be conducted including different LCI modelling principles. These goal definitions may be related to situation A or B (see the corresponding aspect ‘Classifying the decision context as situation A, B and C for building and product LCA’).

2) Practical guidance for building LCA studies

The goal definition needs to clarify the core objective of a building LCA. This goal may be predefined, e.g. by a building certification system, to provide the building LCA for certification purposes. In general, the practitioner needs to define the study’s goal individually.

This definition of the goal serves as the basis for the identification of the study’s scope, which in turn yields the coverage of different contributors to include in the LCA study, such as the building products (Modules A, B, C, D), construction site (Module A5), energy consumption (Module B6), water consumption (Module B7), transport of people (during the use phase of the building) etc.

For building LCA, the EN 15978 guidance should be used by LCA practitioners to define the goal and scope of their study according to the purpose of the assessment. Three applications are identified in EN 15978:

– assistance in a decision-making process, e.g. comparison of design alternatives;
– declaring performance with respect to legal requirements;
– documenting the environmental performance of a building, e.g. for use in labelling.

3) Predefined goal for product and building LCA studies according to EeBGuide study types

The definition of the goal of a study within the context of this guidance document is also broadly predefined through the use of the three study types (screening, simplified and complete LCA). The reporting templates of the EeBGuide also help regarding documentation of the goal of an LCA study.

However, the study type (e.g. screening LCA) may be adjusted, depending on the practitioner. This is the reason why the provisions and guidance for the corresponding aspects remain flexible. For example, for the choice of LCA data for a screening LCA, the EeBGuide recommends using different types of data. Architects may prefer to use building components (e.g. 1 m² of wall, with the possibility of changing the width of structural and insulation products), whereas a construction company may prefer quantifying the impacts of a building design at the level of materials (e.g. kg of steel, or m³ of concrete).

4) Practical guidance for product LCA studies within E2B EI research projects

Within E2B EI research projects, it may be interesting to extend the goal of the project, if relevant. For example, for a product LCA, the primary goal may be to develop a product system model as well as delivering a full LCA study for a specific purpose, such as identifying the environmental impacts of a building design or of a novel product.

In some cases, however, the goal might be required to be extended to secondary applications, e.g. developing an EPD for the corresponding product, or providing the LCA study for building certification purposes. In this case, the same life cycle model can be used if it is suitable according to the relevant PCR (e.g. EN 15804), or to the set of LCA calculation rules of the relevant building certification scheme. The main advantages of extending the goal from the beginning of the study is to reduce the additional effort in e.g. data collection, methodological choices (e.g. use of parameters), reshaping of the product model etc.

However, this type of extension of the goal might be difficult to achieve for innovative products where no detailed PCR exist. In such cases the study should at least comply with the major requirements of the core European PCR (e.g. EN 15804) if the secondary goal is to provide an EPD. In addition, the definition of several goals for a study may make it difficult for the practitioner to meet all the study’s objectives. A trade-off needs to be found between reduced effort through integration of secondary goals and increased effort due to e.g. increased flexibility required of the product model, or multiple results.

An attributional LCA assesses the environmental impact of one quantity unit or one piece of a product. Any scaling-up of the environmental impacts of this product is linear. This means that the environmental and technical consequences (and possibly also the economic consequences) of the life cycle of the assessed system are seen not to have significant impacts on other technical systems, products, etc. This is often seen as a feasible simplification in the process of modelling parts of the real world.

A consequential LCA, by contrast, assesses the environmental impacts of products or technologies with consideration of the indirect effects, i.e. by assessing the consequences of the assessed life cycle on other systems. As an example, the assessment of biofuel might include the consequences of increased pressure for the available land in tropical forests due to energy crop harvesting, or include the assessment of consequences of a shift of technologies due to the reduced availability of one rare earth.

Conducting a consequential LCA may result in special requirements for LCA background data, and typically increases the options or choices within the assessed system. As a consequence, the LCA practitioner is required to make an increased number of assumptions, which may reduce the significance of a result.

The European standards EN 15804 and EN 15978 do not consider consequential LCA. It may be valid for specific cases to conduct a consequential LCA, but for the most common applications of LCA in the building and construction sector an attributional LCA should be the method of choice. If a consequential LCA is conducted, the LCA practitioner needs to fully understand the related methodologies, and therefore make him or herself thoroughly familiar with the corresponding literature.

1) Guidance for the choice between attributional and consequential LCA in the building sector
The practitioner should use attributional LCA (situation A in the ILCD Handbook) for the following applications:

• development of PCR or EPD of building products and technical equipment;
• LCA used for ecodesign of an individual product or building.

The practitioner may use consequential LCA (situation B in the ILCD Handbook) for the following applications:

• building sector policy development (e.g. assessment of the marginal effects of a widespread development of renewable energies or new technologies for products; orientation of new environmental regulations).

Situation C is unclear in the ILCD Handbook, as it is intended not to have a decision support. However, even an internal LCA study in a company always has support, such as benchmarking, or improvement potentials. Generally speaking, most of the time the LCA practitioner in the building sector will rely on situations A or B.

Whereas a single product or building does not change the background system very much (situation A), this will no longer be the case when all the building sector is considered. For example, in France, where many buildings are heated by using electricity, this leads to a winter peak demand when thermal power plants are turned on, resulting in increased CO₂ emissions [Peuportier 2008]. Assessing the entire building stock should relate to a situation B decision context. Under the specific goal and scope, situation B may be used for individual systems that are large enough to potentially influence the background system.

2) Guidance for studies complying with goal and scope definition according to EN 15804/EN 15978
EN 15978 and EN 15804 relate solely to attributional LCA studies. As a result, provisions and guidance that are in line with these standards in terms of scope definition and inventory analysis refer only to situation A (attributional modelling) in the EeBGuide.

3) Specific guidance and current limits for consequential LCA
The use of situation B needs appropriate LCI data. Usually, the practitioner may rely on background databases (providing consequential datasets). The practitioner can refer to the provision ‘6.5.4 LCI modelling for Situations A, B, and C’ for more guidance and rules.

In the LCA community, there is no commonly agreed understanding on how to decide which type of decision context situation should be applied. This is especially true for medium-scale systems (e.g. a neighbourhood or a district) for which no strict recommendations are given in the ILCD Handbook. In these cases, the use of a situation A or B should be justified by providing evidence e.g. on the possible modifications on the background system.

As the distinction between attributional and consequential LCA is currently a much-discussed topic, the practitioner may also be interested in referring to the recent review articles published by [Frischknecht 2010], [Earles 2011] and [Zamagni 2012]. According to [Zamagni 2012] there are still several issues to address in consequential LCA, including the selection of appropriate data, the identification of market mechanisms, and the affected processes that should be included in the system boundaries. The authors state that scenario modelling can be a useful approach in dealing with present mechanisms and future developments. Scenarios can be predictive (what will happen?), explorative (what can happen?), or normative (how can a specific target be reached?).

• the assumptions made are justified;
• the assumptions are documented transparently;
• a sensitivity analysis has been conducted and reported by comparison with the baseline scenario;
• the external review comments on this assessment of future developments are included.

The above restrictions are valid for EPD, and in ILCD the comparative goal justifies certain limitations. In some circumstances, however, the goal of the LCA for a product or building may be to understand the effect of a future development and its implications – for example, what is the implication of a changing energy mix for a highly insulated building or an energy-using product? In these circumstances it can be appropriate to consider the effects of future technology. If this type of LCA is undertaken, it must be very clearly stated that the study differs from a more usual EPD or building LCA.

To assess the impacts of future technological developments, separate scenario modelling may be carried out, if significant impacts on today’s decisions may be expected as a result of future technology shifts.

Such developments could be, for example:

• a shift in the energy mix over a building’s life cycle;
• a shift in the energy efficiency of the building envelope;
• new technologies to recycle construction waste.

Third-party forecast studies or – if this is within the focus of the research – the practitioner’s own forecast studies should be used as the basis for deriving assumptions for future technology shifts.

Any assumptions made, and the resulting modelling consequences, should undergo a third-party review.