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Tag: Study type: Screening LCA

2.3 Procedure for choosing provisions from both CEN TC 350 standards and the ILCD Handbook

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The ILCD Handbook was written by a panel of scientific researchers and experts in LCA, whereas the CEN TC 350 standards were written by a panel of building stakeholders as well as LCA experts. The level of detail varies considerably between the CEN standards (around 50 pages) and the ILCD Handbook (around 1000 pages in total). The main differences between the ILCD and CEN TC 350 standards can be found in their terminology and provisions. For example, EN 15804/EN 15978 proposed new terms such as the ‘functional equivalent’ of a building to adapt the ‘functional unit’ term defined in ISO 14040 and in the ILCD for the building sector. As a result, these documents may often conflict in the definition, the level of detail and finally the provisions to adopt for each LCA step, and for each life cycle stage. A systematic procedure was therefore adopted in the EeBGuide for choosing the basis of the guidance included for each aspect.

As mentioned above, the EeBGuide tries to combine provisions and guidance from the EN 15804 and EN 15978 standards and the ILCD Handbook (see Figure 5). If cases of contradictory approaches appear in the reference sources, then the EeBGuide always tries to state a provision or guidance transparently for both the standard and the ILCD Handbook. As far as possible, the EeBGuide provisions follow the European standards [EN 15804] and [EN 15978] closely. If the standard does not mention a certain aspect, or if it is not very clear on that aspect, provisions and guidance from the ILCD Handbook are provided. Where no existing guidance is available, other provisions are proposed by the EeBGuide.

Figure 5: Procedure for adaptation from the CEN TC 350 standards and ILCD Handbook

Guidance can include links to further interesting or important information, or to examples, or present an interpretation of the standard or the ILCD Handbook. This interpretation is not meant to be a provision, but rather a means to share LCA experiences from LCA practitioners and experts.

2     Methodological approach of the EeBGuide.

2.4.1 Screening LCA

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Purpose

A screening LCA study may serve for an initial (quick) overview of the environmental impacts of a building or a product. The challenge is to adapt the LCA methodology and simplify the use of LCA at the early design stage. With a screening LCA, it is not possible to retrieve detailed results on the environmental performance of a building or a product, and comparative assertions according to ISO 14044 cannot be based on it. Comparisons can be made internally, but these comparisons should not be published. This type of study yields an estimate of the environmental performance, which can be helpful in the early stages of design (e.g. for an architect’s draft design0 in of a research project (e.g. to identify environmental hotspots that require an additional, in-depth assessment).

Completeness of assessment

A screening study would typically focus on the main contributors to the system under assessment, including (but not limited to) the input materials, water and energy use, and the transportation of users (if relevant). In screening LCA, to avoid misleading results, care is needed to ensure that omitted building products are not significant for the chosen environmental indicators. It is also important to use adapted calculation rules for screening LCA (e.g. the use of statistical data for assessing impacts of water consumption). More information on the calculation rules can be found in Table 5.

Cut-off rules, as specified in EN 15978 and EN 15804, and in the ILCD Handbook, may not apply to screening LCA studies for buildings or products. For example, in the early design stages not all the input raw materials and components are known in detail, which means that some of them are omitted. Rather than systematically neglect them, one option is to try to model these omitted processes using default values. Generally speaking, life cycle modules, inputs and services should be omitted only if their insignificance for the corresponding environmental indicator can be scientifically justified.

A screening study might focus on one single indicator or several, and most studies should include PENRT (total use of non-renewable primary energy resources) and if relevant the GWP (global warming potential) and PERT (total use of renewable primary energy resources). As a general rule, a set of between five and seven additional relevant core LCIA indicators can be used (see the corresponding aspect in section 5). They may be taken from either EN 15804 or EN 15978, and from additional indicators described in the ILCD Handbook (if relevant for the purpose of the study).

Data representativeness

In comparison with the other study types, a screening study is likely to be based on generic assumptions, according to the goal and scope of the study. For example, if the goal is to conduct an LCA study within a European project, then the use of generic assumptions for the EU context may be sufficient. However, if the goal is (as in most cases) to conduct an LCA study that is representative within a national context, then generic assumptions for the national context are appropriate. Five major areas related to the representativeness of data can be considered: geography, technology, age, time and precision. It is also important to ensure consistency within the data used.

Geography

The data used in a screening study should, as far as is practical, given the existing time and budget constraints, relate to the country from which the building or product originates, and in which it is built or produced. However, as this is not always possible, it is also acceptable to use assumptions from a neighbouring country (with a similar context), or average European data, or even average global data. In this case, the data used, and their limitations, should be highlighted in the documentation. These provisions do not apply to data on energy, water and waste treatment processes, as national data are preferable (e.g. electricity mix, natural gas) but, otherwise, European data can be used if relevant.

Technology

The data used should represent the technology used as closely as possible. For example, if different heating systems are to be assessed from a product or building perspective, or if a comparison of bearing structures from reinforced concrete against timber framing is intended, then the data should reflect an equivalent state-of-the-art technology.

Precision

Average environmental quantitative information on the building or product may be taken from generic LCA data, or from default values for major components. For other sources of impacts related to the operational energy and water, and to the construction site, refer to the provisions given in the guidance document.

Consistency

A qualitative assessment of whether the LCA methodology is applied uniformly to the various components and processes should be made in relation to the goal and scope of the study.

Documentation

Use the reporting template provided. The minimum requirements for items reported on can be summarized as follows:

  • Definition of the goal and scope
  • Life cycle stages included
  • Main input materials/items included, as well as processes for energy, water etc.
  • Overview of calculation rules, and comment on degree of approximation/uncertainties
  • Impact categories considered
  • Life cycle impact results and interpretation (conclusions)
  • Statement regarding consistency
  • Results

Communication of LCA report and results

Screening LCAs are for internal communication purposes only (e.g. during an architectural competition), not public comparative purposes. A statement about the uncertainty of the results due to the screening process must be included.

Examples of screening LCAs:

  • Building LCA study to identify environmental optimization potentials in the early design stages (for an architect or stakeholder, helping to improve the building design).
  • Supporting documentation for an architectural competition.
  • Comparison of a, innovative new product and an existing one (e.g. within a company).

2     Methodological approach of the EeBGuide.

3.1.1 Implementation of the study type definitions

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Table 5 gives specific information about how the three LCA study types (screening, simplified and complete) are currently implemented within the EeBGuide framework. Screening describes the first approach, where most of the information on the building is still very rough (e.g. within the design stage): thus default values of generic assumptions need to be chosen and used. In a simplified LCA study, detailed data are used, and a greater number of life cycle stages are addressed. Complete LCA reflects the most comprehensive and detailed application of the LCA methodology. For each level, Table 5 highlights those modules that are mandatory, optional because of their minor relevance, or optional because of currently missing data. The term ‘mandatory’ here specifically relates to projects of the Energy-Efficient Buildings Initiative (E2B EI). For other projects, or for the secondary audience of EeBGuide, this can be considered as a guideline.

Note: The term ‘product’ refers to building-related products, construction materials, components and services.

Table 5: Implementation of the different study types for buildings

3     How to use this guidance document

3.1.1 Implementation of the study type definitions

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Table 5 gives specific information about how the three LCA study types (screening, simplified and complete) are currently implemented within the EeBGuide framework. Screening describes the first approach, where most of the information on the building is still very rough (e.g. within the design stage): thus default values of generic assumptions need to be chosen and used. In a simplified LCA study, detailed data are used, and a greater number of life cycle stages are addressed. Complete LCA reflects the most comprehensive and detailed application of the LCA methodology. For each level, Table 5 highlights those modules that are mandatory, optional because of their minor relevance, or optional because of currently missing data. The term ‘mandatory’ here specifically relates to projects of the Energy-Efficient Buildings Initiative (E2B EI). For other projects, or for the secondary audience of EeBGuide, this can be considered as a guideline.

Note: The term ‘product’ refers to building-related products, construction materials, components and services.

Table 5: Implementation of the different study types for buildings

G-01 Goal definition for building and product LCA

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Aspect G-01 Goal definition for building and product LCA
Description
 According to ISO 14040-44 and the ILCD Handbook, the goal definition of a study is a key LCA requirement, as it guides all the detailed aspects of the scope definition, which then determine the LCI and LCIA provisions. Special attention should be paid to this first step of the LCA methodology, which will influence the study results and determine their applicability. Generally speaking, the goal definition should be documented in detail.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?

Related study objective

 ☒ stand-alone LCA ☒ comparative assertion

Related study phase

 ☒ ☐ ☐ ☐ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

Relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions The goal definition for a building or product LCA study should be defined according to the ILCD Handbook (e.g. by defining the context and the intended use of the assessment).The documentation should also be in line with ISO 14044, EN 15978 and EN 15804.
Rules from:

EN 15978
  • 6 Purpose of the assessment
  • 7 Specification of the object of assessment

EN 15804
  • 5.1 Objective of the PCR

ILCD

 5 Goal definition – identifying purpose and target audience 
Provisions: 5.2 Six aspects of goal definition

  • I) SHALL – Intended applications
  • II) SHALL – Limitations of study
    • II.a) Impact coverage limitations
    • II.b) Methodological limitations
    • II.c) Assumption limitations
  • III) SHALL – Reasons for study
    • III.a) Internal
    • III.b) External
    • III.c) Database developer perspective
  • IV) SHALL – Target audience of study
  • VI) SHALL – Comparisons involved?
  • VII) SHALL – Commissioner

Provisions: 5.3 Classifying the decision context

  • Provisions 5.4: Need for flexibility versus strictness
  • I) SHALL – Product-group and process-type specific guides and PCRs
    • I.a) Need for specific guides and PCRs
    • I.b) Specific guides and PCRs overrule ILCD Handbook

Provisions 5.5: Optionally extending the goal

  • I) MAY – Extending the goal?

15 Annexe D: Avoiding misleading goal and scope definition and results interpretation
Guidance
 Goal definition is a crucial aspect of each LCA study. The practitioner should note that this step has implications for all the following general aspects: scope of the study, life cycle inventory analysis, impact assessment, interpretation, reporting and critical review, as well as all the life cycle stage aspects of products and buildings (i.e. aspects for Modules A, B, C and D according to EN 15804/EN 15978). As a result, it is directly connected to all the provisions/guidance provided in the EeBGuide.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’.One 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.

G-02 Classifying the decision context as situation A, B, and C for building and product LCA

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Aspect G-02 Classifying the decision context as situation A, B, and C for building and product LCA
Description
 The ILCD Handbook distinguishes between different decision contexts for LCA studies. This distinction is part of the goal and scope definition of an LCA study, and has major implications for further definitions of system boundaries and modelling principles, etc. According to the ILCD Handbook, situation A modelling is defined as ‘micro-level decision support’, whereas situation B is characterized as ‘meso- and macro-level strategic (‘policy’) decision support’. Thus situation A refers primarily to product- or process-related decision support studies, whereas situation B applies to strategic decision support studies. It is important for practitioners, to understand under which situation an LCA study has to be established. In addition, the differentiation of when to use situation A or situation B might be unclear in the building sector.

Related study objective

 ☒ stand-alone LCA ☒ comparative assertion

Related study phase

 ☒ ☐ ☐ ☐ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

Relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions Situation A (attributional LCA) should be used for individual product or building LCA studies that do not have a major influence on the background system (such as the energy supply).Situation B (consequential LCA) should be used in modelling specific cases where macroeconomic systems are significantly affected through the use and the dimension of the assessed technology. If an LCA study is believed to be related to situation B, the ILCD Handbook and LCA literature should be consulted for guidance on how to proceed.
Rules from:

ILCD:

5.3 Classifying the decision context as Situation A, B, or C

Table 7: Combination of two main aspects of the decision context: decision oriented and type of consequences in background system or other systems [ILBD 2010a]

Provisions: 5.3 Classifying the decision context

Provisions: 6.5.4 LCI modelling provisions for Situations A B, and C

 

Some examples of situation A, B and C modelling are mentioned in the ILCD Handbook.

Situation A refers to single product assessments that will not change the background system (e.g. when it refers to a limited share of the total production of an industrial sector). The most relevant application of situation A (micro-level decision support) are:

  • ecodesign/simplified LCA;
  • development of specific, average, generic unit process or LCI results for the identified intended applications under situation A;
  • development of Product Category Rules;
  • development of a life-cycle-based Type III environmental declaration (EPD) for a specific good.

Situation B refers to life-cycle-based decision support that will have consequences outside the analysed system boundaries via market mechanism changes. The most relevant applications of situation B (meso/macro-level decision support) are:

  • policy development (e.g. spreading renewable energy technologies or not; forecasting unconventional technology development in the future);
  • policy information (e.g. identifying product groups with the largest environmental improvement;);
  • development of specific, average, generic unit process or LCI results for the intended applications identified under situation B.

 

For unclear situations, the ILCD Handbook gives the following advice:

“In this situation, the guiding criteria shall be whether the consequences of the analyzed decision alone are big enough to overcome related thresholds and/or other constraints and result in large-scale consequences in the installed production capacity outside the foreground system. Then: Situation B. If not: Situation A.”

The last option is to use situation C “Accounting” if the LCA is not intended to be used as for decision support. Situation C1 (“including interactions with other systems”) is distinguished from situation C2 (“excluding interactions with other systems”). “The most relevant applications are e.g. for C1:

  • Monitoring of environmental impacts of a nation, industry sector (only for situation C1);
  • Policy information (identifying product groups with the largest environmental impact);
  • Corporate or site environmental reporting”
Guidance
 Most of the LCA studies published in the building sector have used the LCA approach called attributional modelling (or situation A in ILCD). This type of modelling is the most familiar to the LCA practitioner. Alternative modelling choices are available, especially consequential modelling (or situation B in ILCD). This modelling approach assesses the consequences of the introduction of a new technology or new processes by looking at the marginal effects. The questions addressed are different in these two modelling approaches.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 heating 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?).

G-03 Future technical developments and innovation

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Aspect G-03 Future technical developments and innovation
Description
 This aspect includes the possibility of considering the effects of future developments with regard to technologies, materials and end-of-life options (e.g. scenarios on energy recovery, or recycling) within a building LCA. In the current business world, technologies and production techniques are changing rapidly. In contrast, building and product LCAs are based on today’s available technology (the precautionary principle). Some major technical systems may change significantly within the coming decades. Hence a modelled option may be preferable, based on today’s general conditions, but may not be the preferable option under future conditions.How can technical developments and innovation be dealt in product or building LCA studies?

Related study objective

 ☒ stand-alone LCA ☒ comparative assertion

Related study phase

 ☒ ☐ ☐ ☐ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

Relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions EPDs for building products, and building-level LCA assessments, are based on the attributional LCA approach, and the European standards developed for the industry are clear that they should be considered on the basis of current practice. EN 15978 mentions that technologies should be rated by economical and technical feasibility. EN 15804 emphasizes that the scenarios should be practical, and be based on today’s technology. This reflects the baseline scenario.Where relevant, alongside EPD and building-level LCA studies, the effect of changes of production techniques, materials etc. may be shown by a separate scenario within a sensitivity analysis. All assumptions have to be documented, and should be based on reliable sources. For comparative assertions the consideration of future developments should be avoided or, where they are considered, they must be treated in the same way for both product systems.Future developments may be described within separate scenarios, where:

  • 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.
Rules from:

EN 15978

8.7.4 Scenarios for waste processing for reuse, recycling and energy recovery – Module C3

EN 15804

 6.3.8 Developing product level scenarios

ILCD

 Provisions: 7.4.3.7 Future processes and elementary flows
Guidance
 In every study, a baseline scenario reflecting current technology should be assessed. According to EN 15804 and EN 15978, it is important that scenarios for the use and EoL stages be based on today’s technologies. Scenario-based quantifications can be provided as accompanying information, and may be included in the assessment.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.

Back to 5.2.  Goal and Scope

G-05 Scope definition for building and product LCA

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Aspect G-05 Scope definition for building and product LCA
Description

According to [ISO 14040], [ISO 14044], and the ILCD Handbook, the scope definition of a study is the step where the main requirements related to methodology, quality, reporting and review in accordance with the goal of the study (i.e. based on the reasons for the study), the decision context, the intended applications, and the addressees of the results [ILCD 2010c] are stated. Examples of requirements include the function, functional unit and reference flow definitions, derivation of system boundaries, and cut-off criteria (completeness).

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

Related study objective

  ☒ stand-alone LCA ☒ comparative assertion

Related study phase

 ☒ ☐ ☐ ☐ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

Relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions

The scope definition of a study should be defined according to the context and the intended use of the assessment.

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

6 Purpose of the assessment

7 Specification of the object of assessment

EN 15804:

6.2 Life cycle stages and their information modules to be included

6.3 Calculation rules for the LCA

ILCD:

6 Scope definition – what to analyse and how

Provisions 6.2.1 Consistency of methods, assumptions, and data

Provisions 6.2.2 Reproducibility

Provisions 6.3 Types of LCA deliverables and intended applications

Provisions 6.4 Function, functional unit, and reference flow

Provisions 6.5.4 LCI modelling provisions for situations A, B and C

Provisions 6.6 Deriving system boundaries and cut-off criteria (completeness)

Provisions 6.7 Preparing the basis for the impact assessment

Provisions 6.8.2 Technological representativeness

Provisions 6.8.3 Geographical representativeness

Provisions 6.8.4 Time-related representativeness

Provisions 6.9 Types, quality and sources of required data and information

Provisions 6.10 Comparison between systems

Provisions 6.11 Identifying critical review needs

Provisions 6.12 Planning reporting

ISO 14044:

4.2 Goal and scope definition
Guidance

1) General guidance for product or building LCA studies

This step is closely linked to the goal definition. It is recommended that the LCA practitioner does not start from ‘zero’, but rather follows EN 15804 and EN 15978 if the scope definition within these standards is relevant for the context of the study. If not, it is recommended that the ILCD guidance on how to define the different aspects of the scope be used (see the rules from ILCD).

2) Practical guidance for product and building LCA studies according to the scope definition of EN 15804/EN 15978

The scope of the study defines the various 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), and transport of people (during the use phase).

The inclusion of any module depends on the goal definition, the stage of the project, and the LCA practitioner. Generally speaking, all the provisions for scope definition in EN 15804 and EN 15978 should be applied.

3) Predefined scope of product and building LCA studies according to EeBGuide study types

The definition of the scope of a study within the context of this guidance is also broadly predefined through the study type (screening, simplified or complete LCA). Provisions for aspects such as the completeness of the assessment (e.g. adapted calculation rules, system boundaries and cut-off-criteria), data representativeness and type (e.g. use of default values), documentation and communication help the definition of the scope. The reporting templates of the EeBGuide also help regarding documentation of the goal and scope of an LCA study.

G-06 (Buildings) / G-07 (Products) Functional equivalent

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Aspect G-06 (Buildings) / G-07 (Products) Functional equivalent
Description
 According to [EN 15643-1], the functional equivalent is a representation of the required and quantified functional and/or technical requirement for a building or an assembled system (part of works), which is used as a basis for comparison. Usually, assessments of individual objects form part of the decision-making process regarding, for instance, whether to build a new building or refurbish an existing building, or which are the most appropriate design options. In such cases comparison should be made only on the basis of functional equivalents. For this reason, in comparative studies between different systems/options, it is essential to define the functional equivalent.How should the functional equivalent be correctly defined?

Related study objective

 ☒ stand-alone LCA ☒ comparative assertion

Related study phase

 ☒ ☐ ☐ ☒ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

Relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions At the building level, the functional equivalent should be defined with regard to EN 15978. it needs to include the building type, relevant technical and functional requirements, the pattern of use and the required service life. Other specific requirements or conditions may be relevant for inclusion in the information on the functional equivalent.The functional equivalent concept may be used at the sub-building level. EN 15804 defines the rules for the functional unit to ensure that the comparison is consistent (e.g. for assembled systems or components). In such cases the basis for the comparison is the entire building, ensuring that the same functional requirements are met.
Rules from:

EN 15978

 

 7.2 Functional equivalent

EN 15804

6.3.2. Functional unit

5.3 Comparability of EPD for building products

ILCD

 Provisions: 6.4 Function, functional unit, and reference flow

  • I) SHALL – Identify system or process
  • II) MAY – Photos, specifications
  • III) SHALL – Identify function(s) and functional unit(s)
  • IV) SHALL – Functional unit, details
    • IV.a) Function provided (what),
    • IV.b) in which quantity (how much),
    • IV.c) for what duration (how long),
    • IV.d) to what quality (in what way and how well is the function provided (what)
  • V) MAY – Obligatory and positioning properties
  • VI) SHALL – Measurement methods
  • VII) SHOULD – Alternatives and complements to the functional unit
    • VII.a) Materials and other application unspecific products
    • VII.b) Monofunctional processes
    • VII.c) Multifunctional processes
  • VII) SHOULD – Highly variable function
  • VII) SHALL – Comparative studies
Guidance
 In practice, a building has many different functions, and it is important to define correctly what is included in the functional equivalent. ISO and CEN standards dealing with the sustainability of buildings propose that the reference flow (which is conventionally called the ‘reference unit’) be differentiated from the functional unit (which is conventionally called the ‘functional equivalent’).In EN 15978, the reference unit (i.e. the expression of the results in terms of m² or number of people) is differentiated from the functional equivalent, which includes various aspects related to the characteristics of the building. At the building level, EN 15978 defines the functional equivalent, whereas at the product level, EN 15804 defines the functional unit.

  • Example of the functional equivalent of a building:

Type of building: Office building; 4000 m² net floor area

Use: net floor area heated or cooled to specified temperature level

Relevant technical and functional requirements: heated and cooled rooms with a temperature range between 20°C and 26°C; air change rate of 30m³/(h*person); lighting level 300 lux; see also specifications in national standards.

Pattern of use: 200 workers; working time from 07.00 am till 06.00 pm, 5 days per week, 48 weeks per year.

Design service life: 50 years

  • Example of the functional equivalent of an assembled system:

Type of system: Transparent solar thermal collector

Use: production of thermal energy in kWh per façade area in m². Relevant technical and functional requirements: U-value of 1.0 W/(m²K); function as shading device, reducing solar gains inside the building;

Design service life: 20 years

More information regarding the definition of the functional equivalent is linked to benchmarking criteria. Such concepts are much more developed in another European project (FP7) called ‘SuPerBuildings’. Interested practitioners can look at the online deliverable D5.2 ‘Benchmarking criteria for sustainable buildings in Europe’ on the website of the project.

G-06 Distinction between the declared unit and the functional unit

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Aspect G-06 Distinction between the declared unit and the functional unit
Description
 The functional unit represents the quantified performance of a product system for use as a reference unit for the LCA study. It is the unit of scale or reference on which the LCA results are based, and relates to the given function of the product. In other cases, the functional unit should be defined according to the future use of the building. A functional unit comprises a function, a quantity, a duration and a quality. The declared unit is used instead of a functional unit when the precise function of the product at the building level is not stated or known, or when the LCA does not cover a full life cycle. It is necessary to distinguish between these two concepts for product LCA, and to give operational guidance.

related study objective

 ☒ stand-alone LCA ☒ comparative assertion

related study phase

 ☒ ☐ ☐ ☐ ☐
goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

relevant for
new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions The practitioner should refer to EN 15 804 and the ILCD Handbook for the correct definitions of the functional unit and the declared unit.

The declared unit should be used for raw materials that are not implemented directly in the building, and for non-application-specific products.

In other cases, the functional unit should be defined according to the future use of the building. A functional unit comprises a function, a quantity, a duration and a quality.

Under special conditions (e.g. if a building product has a rather large number of possible applications in a building), then the declared unit, as defined in EN 15804, may be more appropriate than the concept of the functional unit, as the functions provided by a construction product are often closely related to the way that the product is incorporated in the building, and this cannot be known at the point at which the product is assessed.
Rules from:

EN 15804

6.3.1 Functional unit6.3.2 Declared unit

ILCD

 Provisions: 6.4 Function, functional unit, and reference flowI) SHALL – Identify system or process

II) MAY – Photos, specifications

III) SHALL – Identify function(s) and functional unit(s)

IV) SHALL – Functional unit, details

         IV.a) Function provided (what),

         IV.b) in which quantity (how much),

         IV.c) for what duration (how long),

         IV.d) to what quality (in what way and how well is the function provided (what)

V) MAY – Obligatory and positioning properties

VI) SHALL – Measurement methods

VII) SHOULD – Alternatives and complements to the functional unit

         VII.a) Materials and other application unspecific products

         VII.b) Monofunctional processes

         VII.c) Multifunctional processes

VII) SHOULD – Highly variable function

VII) SHALL – Comparative studies

ISO 14044

 4.2.3.2 Function and functional unit
Guidance
 1) Specific guidance for defining the declared unitThere are two cases when it is relevant to define a declared unit. The first is for raw materials (e.g. cement, gravel) for which a functional unit does not really make sense. The second is for products that can be used in a wide variety of different or simultaneous functions in the building or construction works: for example, a timber section might be used in upper floor construction, in a partition wall, in fencing or in joinery. For each of these functions, the wastage in construction and the service life of the timber might be different. Similarly, a concrete block could be used in either an internal or an external wall, and with thin joint or normal mortar; each of these options will impact differently on the thermal performance of the block in the building or construction works. In this second case, a declared unit is used, allowing the relevant data to be provided and aggregated at the building level, where the function of the product as installed can be considered over the building life. Examples of declared units include:

  • by item, e.g. 1 brick, 1 window (dimensions to be specified), 1 lighting-fitting, 1 radiator;
  • by mass, e.g. 1 kg of cement;
  • by length, e.g. 1 m of pipe, 1 m of a beam (dimensions must be specified);
  • by area, e.g. 1 m2 of wall elements, 1 m2 of roof elements (dimensions must be specified);
  • by volume, e.g. 1 m3 of timber, 1 m3 of ready-mixed concrete.

 

2) Specific guidance for defining the functional unit

For product LCA (e.g. EPD), the functional unit has to be closely defined with the company that commissions the LCA or EPD study.

For cradle-to-gate and cradle-to-site product LCA data, the function of the product within the building or construction works is uncertain, and it is therefore not easy to find a functional unit, which needs to include information on the required functional performance of the product within the building or construction works over the full life cycle. Nevertheless, during discussions on the development of CEN TC 350 the recommended route was to identify reasonable scenarios and include information for one or more of these scenarios. In defining such a scenario, much of the required information to describe a post-gate life cycle stage would originate from the building, and would be related to the product being studied.

The functional unit has a quantity (e.g. 1 m²), a duration (e.g. ‘maintaining the function over 50 years’) and a quality e.g. ‘“to ensure a thermal resistance of 2 m²/W.K’). It is closely connected to the definition of the relevant service life of the product (cf. the corresponding aspect).

For comparative purposes, different, simultaneously applying functions may be relevant. With the definition of the functional unit, all relevant functions should be covered.