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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-04 Comparative assertion for building or product LCA

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Aspect G-04 Comparative assertion for building or product LCA
Description

Comparative assertion is an environmental claim regarding the superiority or equivalence of one building product (or one building design) compared with a competing building product (or an alternative building design) that performs the same function. Usually, the comparison of alternative products, systems or buildings is the main goal of a comparative LCA study. Different aspects have to be taken into account to conduct a meaningful and robust comparative assertion. One of these is the functional equivalence between the systems under comparison (see the ‘functional equivalent’ aspect), but there are other aspects that need to be considered, such as the system boundary, the background database, the life cycle inventory, and the life cycle impact assessment methodology applied.

How can a comparative assertion be made in building LCA applications?

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

In a comparative study, it must be ensured that the systems being compared are equivalent in function. According to ISO 14044 and ILCD, the same functional unit, system boundary, data quality requirements and allocation procedures have to be applied.

EN 15978 provides the practitioner with rules to be considered in the comparison of two buildings. The comparison also has to use the same environmental indicators, using those defined in the standard and in the ILCD Handbook.

The provisions of EN 15804 may be used under very specific conditions to compare cradle-to-grave product alternatives (cf. guidance).

 
Rules from:
 EN 15978:

Purpose of the assessment

EN 15978 states that it can be used for “assistance in a decision-making process, for example: comparisons of the environmental performance of different design options”.

EN 15804:

5.1 Objective of the PCR

EN 15804 states that the “declarations based on this standard are not comparative assertions.”

ISO 14040:

4.3 Key features of an LCA

5.2 Goal and scope definition

6 Reporting

7.2 Need for critical review

ISO 14044:

4.2.2 Goal of the study

4.2.3 Scope of the study

4.2.3.7 Comparison between systems

4.4.5 LCIA intended to be used in comparative assertions intended to be disclosed to the public

5.3 Further reporting requirements for comparative assertion intended to be disclosed to the public

ILCD:

6.10 Comparison between systems

6.10.3 Considered alternatives, the functional unit, and assumptions

6.10.4 Methodological, assumptions and data consistency

6.10.5 Data quality requirements

6.10.6 Identical parts of the compared systems

6.10.7 Scenarios in support of comparisons

6.10.8 Carbon footprint studies and other selected comparisons

 

Main provisions for all comparative studies (summary of the ILCD Handbook):

I) ISO 14044:2006 provisions for comparison assertions shall also be applied to non-assertive comparative studies.

II) All aspects of the goal and scope definition shall be addressed consistently especially for: LCI model, assumptions, data quality.

III) Uncertainty and accuracy calculation shall support this analysis.

IV) The completeness/cut-off (in%) shall be met for mass and energy, next to the overall environmental impact.

V) The excluded processes that are identical for all alternatives may be left out of all models.

VI) An LCIA shall be performed for LCA studies intended to support comparative studies (for public communication).

VII) If only one impact category (e.g. carbon footprint) is considered for those studies, it shall highlight that the comparison is not suitable to identify environmental preferable alternatives. This applies unless it is demonstrated that the two compared systems do not differ in other relevant environmental impacts to a degree that would change the main conclusions.

 

Main provisions for studies with similar functional equivalent (summary of the ILCD Handbook):

VIII) The compared systems shall have the same functional unit.

IX)  The study should include potentially environmentally better market relevant and available alternatives, as otherwise the study would be considered misleading.

X) The selected functional unit should reflect well-justified typical or average production/operation/use scenarios; it shall be agreed with the affected stakeholders.

XI) If the system needs to be replaced to meet the required duration of performance of the compared functional unit, the replacement should consider that potentially a newer system will replace the initially used model.

XII) For comparative micro-level studies (Situation A), each compared scenario shall be complemented with assumption scenarios of reasonably best and worst cases. Uncertainty calculation shall be performed.

XIII) For comparative meso/macro-level (situation B): the scenarios for each of the analysed alternatives shall apply the modelling guidance of situation A, except for processes affected by large-scale consequences of the analysed decision.

XIV) Involvement of interested parties in review.
Guidance
  

For building LCA applications, comparative assertions are typically conducted to choose among design alternatives.

The major focus of the LCA practitioner has to lie on defining two alternatives that are truly comparable. Therefore special attention should be directed to identifying all functions that a design alternative has. This may include technical functions, e.g. structural functions, and building physical functions, such as ensuring specified quality levels of the indoor environment, but also architectural and aesthetic functions. Therefore design alternatives should always be agreed within the planning team, including the architect, structural engineers, building physics and energy performance experts. If the functions of two design alternatives are not truly comparable, the planning team should identify additional solutions to ensure comparable features, and these should be included in the comparative LCA study.

Users who are not LCA experts typically use dedicated LCA tools for comparing their building’s design alternatives. Such tools may support the choice of adequate – comparable – design alternatives, and assist in conducting the LCA study, especially with regard to the comparability of background data, etc. (see below).

 

1) Practical guidance when comparing building design alternatives

Because design software contains built-in methodological decisions (functional unit, system boundaries, cut-off criteria, etc.), as well as built-in databases, it is generally important not only to apply generally uniform methodological decisions, but also to use the same software when comparing two building design alternatives.

Concerning the background database used for the comparative assertions, the user can look at the methodological report or user manual of the LCA software for buildings to check for consistency according to the ICLD handbook.

Useful information on the use of LCA in the design of buildings can be found in one of the deliverables of the LoRe-LCA European project (FP7), available online.

 

2) Comparative assertion for product LCA based on EN 15804 in E2B EI research projects

Under specific conditions, it may be possible to compare a regular product and an innovative product following EN 15804 provisions, if the product model is from cradle to grave. All the other provisions of EN 15804 should be applied, if necessary, to comply with the comparative assertion rules according to ILCD; otherwise use the ILCD provisions if no provisions exist in the EN 15804 standard.

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-07 (Buildings) / G-08 (Products) Functional equivalent vs. functional unit vs. declared unit

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Aspect G-07 (Buildings) / G-08 (Products) Functional equivalent vs. functional unit vs. declared unit
Description
 ISO 14040, ISO 14044 and EN 15804 define a functional unit; EN 15804 also defines a declared unit. EN 15978 defines a functional equivalent.What are the differences, and when should which term be used?

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 ISO 14040 and 14044, as the basic LCA standards, define the ‘functional unit’ as the quantification of the performance of a product system, and specify that is used as the reference unit for the LCA and any comparative assertion.The term ‘functional equivalent’ is defined in EN 15978 as denoting the technical characteristics and functionalities of the building that is being assessed.The term ‘functional unit’, as defined in EN 15804, refers to the quantification of identified functions or performance characteristics of products. The function/performance characteristics of the product are defined at the building level. The functional unit is used primarily as the reference unit for the product LCA study.The term ‘declared unit’ is specific to product LCAs, as defined in EN 15804. It is used instead of the ‘functional unit’ if the specific function of a product at the building level is not known. EN 15804 states that the declared unit shall be used if an LCA study does not cover the entire life cycle (‘cradle to grave’), but only certain modules (e.g. only ‘cradle to gate’).The terms should be used in line with the definitions of the standards to allow for improved consistency of LCA studies within the construction sector.
Rules from:

EN 15978

 7.2 Functional equivalent

EN 15804

 5.3 Comparability of EPD for building products
6.3.1 Functional unit
6.3.2 Declared unit

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
o IV.a) Function provided (what),
o IV.b) in which quantity (how much),
o IV.c) for what duration (how long),
o 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
o VII.a) Materials and other application unspecific products
o VII.b) Monofunctional processes
o VII.c) Multifunctional processes
• VII) SHOULD – Highly variable function
• VII) SHALL – Comparative studies
Guidance
 The distinction between functional unit, declared unit and functional equivalent is specific to the European construction sector, as they are defined in the CEN standards. LCA practitioners who are not thoroughly familiar with these standards may find it difficult to understand the details of this differentiation.In general life cycle thinking, and for the practical purpose of conducting an LCA, the differences in definition and understanding are not critical to conducting an LCA study. All definitions essentially require the technical performance of the object of assessment to be quantified, and they require a comparative quantification for the case of comparative assertions and meaningful reference units, if the results of an LCA study are intended to be used elsewhere (e.g. the results of a product LCA to be used in a building LCA).For practical application, it is recommended that the terminology of the standards be used. It is essential for the success of an LCA study to define the relevant functions carefully, and to identify the appropriate reference unit, as this is the essential basis for any comparison and/or reuse of LCA data.

G-08 Reference study period

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Aspect G-08 Reference study period
Description
 The reference study period (RSP) is defined as the time period for which the time-dependent characteristics of the object under assessment are analysed. The RSP determines the use phase of the assessed building or product. Maintenance, repair, replacement and refurbishment activities, as well as operational energy and water use, are highly sensitive to the RSP definition, and may contribute differently to the environmental impacts over the life cycle.Depending on the type of building or product to be assessed (e.g. existing or new), how should the reference study period be 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 The reference study period is generally not predefined, as there is a multitude of different conventional study periods for buildings all over Europe.For comparison purposes, a reference study period of 50 years can be assumed as a baseline scenario.For comparative assertions (comparison of two buildings or building types), the same reference study period has to be applied.
Rules from:

EN 15978

 7.3 Study reference period

EN 15804

 6.3.3 Reference service life (RSL)
Guidance
 For building LCAs, common reference study periods for different European countries and purposes can be found in Annex A. To select an adequate reference study period, it is recommended that conventional values that may have been agreed for a specific country or building type be used, and that this number be used to ensure comparability of the results of the study.In the EeBGuide, the value of 50 years for the baseline scenario is defined to provide consistency among studies that are set up in a comparative environment, such as research projects of the E2B Initiative. For other comparative studies, other reference study periods may be chosen (if relevant).

G-09 Object of assessment with regard to energy-efficient build-ings

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Aspect G-09 Object of assessment with regard to energy-efficient buildings
Description
 Life cycle assessment is a flexible methodology that can be applied to all kinds of product or building. It is important to specify whether the LCA methodology has to be adapted in terms of system boundaries or cut-off rules when applying it to an energy-efficient building.

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 Life cycle assessment is a flexible methodology that can be applied to all kind of building, whatever their environmental performance (or energy efficiency). For this reason, the definition of the object of assessment does not need to explicitly define specific levels of energy efficiency.The current and forthcoming definitions of an energy-efficient building may, however, support an LCA approach (i.e. from cradle to grave), as opposed to a focused assessment that looks only at the environmental aspects linked to operational energy use.
Rules from:

EN 15978

 7. Specification of the object of assessment
Guidance
 The energy efficiency of buildings during their operational stage generally does not influence definition of the object of assessment, as for a building LCA this generally refers to the building’s entire life cycle. For this purpose, it is recommended that national definitions across Europe be referred to , such as the German ‘passive houses’ or French ‘low energy buildings’ (BBC) and ‘positive energy buildings’(BEPOS).The main information concerning the object of assessment should be considered in the functional equivalent; other, secondary information may be also reported regarding the scope of the study.

G-10 Definition of system boundaries for new buildings

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Aspect G-10 Definition of system boundaries for new buildings
Description
 A clear definition of the system boundaries is needed for improved understanding and interpretation of the LCA results, as well as to enable them to be used for comparative assertions (e.g. choice of design alternatives) or stand-alone LCA (e.g. benchmarking purposes).How should this system boundary be defined for new buildings?

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 For a new building, the system boundary should include all stages of the life cycle. This includes all the upstream and downstream processes needed to establish and maintain the function(s) of the building, from the acquisition of raw materials to their disposal, or to the point where materials exit the system boundary, either during or at the end of the building life cycle.For the inclusion of specific contributors (e.g. transport of people, water consumption etc.), the definition of the system boundaries is directly linked to the goal and scope definition (see the corresponding aspects).EN 15978 gives clear rules for setting the system boundary of a building. These rules follow the ‘modularity principle’: that is, where processes influence the building’s environmental performance during its life cycle, they should be assigned to the module in the life cycle where they occur. The system boundary for new buildings should be defined according to EN 15978 and the different study types (screening, simplified or complete).
Rules from:

EN 15978

 7.4.2–7.4.6 boundaries“The system boundary determines the unit processes that are taken into account for the object of assessment.For a new building, the system boundary shall include the whole life cycle.”
Guidance
 The rules given in EN 15978 should be applied (see above). This covers the entire building life cycle as defined with regard to the study type used. The system boundaries include the entire building and its foundations, the building’s curtilage in the building’s site and connected exterior works. In addition, the study type’s definitions should be applied.

G-12 (Buildings) / G-11 (Products) Cut-off rules for screening, simplified, complete LCA

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Aspect G-12 (Buildings) / G-11 (Products) Cut-off rules for screening, simplified, complete LCA
Description
 Cut-off rules enable LCA practitioners to conduct LCA without having to model 100% of the product system. According to the ILCD Handbook, the cut-off criteria refer to the omission of non-relevant life cycle stages, activity types, specific processes and products and elementary flows from the system model. Cut-off rules are quantified in relation to the percentage of environmental impacts that have been approximated to be excluded via the cut-off. The apparent paradox is that one must know the final result of the LCA to be able to know which processes, elementary flows etc. can be left out [ILCD, 2011a]. But, if one knew the 100% impacts of a product, then there would be no need for a cut-off. In practice, the total inventory is always unknown, but must be extrapolated from the measured or calculated data.What should the cut-off rules be for a product LCA or a building LCA?

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 In general, ILCD provisions should be followed for the cut-off rules.For product and building LCA studies complying with EN 15804 and EN 15978 goal and scope definition, the cut-off rules should be adopted.For product and building LCA studies that comply with EeBGuide predefined study types, the cut-off rules should be adopted. They are defined to allow for a simplification of LCA, and in particular to reduce the complexity of the study.For screening and simplified building LCA, the practitioner should refer to the list of building products and technical equipment to take into account. The others remain optional – to date – owing to potentially missing data. However, they may be included if default values exist for these building products or technical equipment at the European level.For complete LCA studies, cut-off rules should be applied primarily according to the ILCD Handbook, but if this is not achievable in practice,  they may be applied according to EN 15804/EN 15978 (in this case, the study type is not entirely a complete LCA).
Rules from:

EN 15978

 7.4.3 Criteria for the exclusion of inputs and outputs

EN 15804

 7.3.5 Criteria for the exclusion of inputs and outputsThe cut-off rules given in EN 15804/EN 15978: “All inputs and outputs to a (unit) process shall be included in the calculation, for which data are available. Data gaps may be filled by conservative assumptions with average or generic data. Any assumptions for such choices shall be documented; In case of insufficient input data or data gaps for a unit process, materials and processes can be omitted, if the process contributes with less than 1% of mass or renewable or non-renewable primary energy of the total, and all excluded materials and processes do not exceed 5% of total energy use and mass.”

ILCD

 6.6.3 Quantitative definition of system boundaries – the cut-off criteria
ILCD states: “The application of cut-off criteria has to consider two main aspects: the translation of the cut-off criteria into operational criteria during data collection of the individual unit-processes and – before that – the procedural issue of how to overcome an apparent paradox:The apparent paradox is that one must know the final result of the LCA (so one can show that the omission of a certain process is insignificant for the overall results) to be able to know which processes, elementary flows etc. can be left out. This paradox is solved through the iterative approach used when performing an LCA, as described in ILCD Chapter 4 and with more details on the inventory part in ILCD Figure 5: the initial settings are to be revisited once or several times and refined in view of the outcome of the subsequent LCI data collection, modelling (including of alternative scenarios), LCIA results calculation, and interpretation (especially contribution, sensitivity, completeness checks and uncertainty analysis). These iterative steps are to be repeated until the results meet the completeness, accuracy and precision requirements as needed for the intended applications of the LCI/LCA study.” Provisions: 6.6 Deriving system boundaries and cut-off criteria (completeness)“VIII – SHALL Quantitative cut-off criteria

VIII.a) Overall environmental impact

VIII.b) Identify the aimed-at cut-off”

ISO 14044

 4.2.3.3.3 Criteria for the exclusion of inputs and outputs
Guidance
 Cut-off rules should not be used to hide results. Therefore it is mandatory to provide verifications for excluded parts.The application of cut-off rules is always highly dependent on the specific circumstances and the product; no general approaches can be defined, but some PCR documents for EPD or labelling schemes define specific cut-off rules, or the extent of the materials and products that should be included. Information from these sources can be stated when the exclusion of materials and products is justified. If appropriate data are available, they should be included in the LCA. If not, then conservative assumptions should be made, and documented transparently. If no appropriate data are available at all, cut-off rules can be applied and the respective aspect can be left out, which should be documented transparently with very special care when comparing product systems (ISO 14044: 4.2.3.3.3).

1) Specific guidance for product LCA studies
Cut-off rules for building product LCA can be defined, e.g. for the exclusion of capital equipment of the production plant, or the exclusion of ancillary materials such as plastic packaging of a raw material in the upstream processes.Practitioners should refer to the existing common rules in the background LCI database for the cut-off rules that should be applied. Generally speaking, the background data should not be modified to comply with the cut-off rule of simplified approaches such as EN 15804. The cut-off rules are defined mainly to ease data collection and modelling for the foreground data. For specific applications such as EPD, generic background data may be pre-verified, i.e. the cut-off rules are compliant with the PCR/EPD programme, so that the practitioner does not need to be concerned with this issue.

Practical guidance on the cut-off rules can be found in dedicated PCR for building products and technical equipment. Generally speaking, simplified approaches such as EPD may have a 5% cut-off rule in mass or in energy for the corresponding life cycle stage. However, it is generally recommended that the available LCI of the raw materials be accounted for, if available, rather than systematically neglect them to comply exactly with the 5% cut-off. The cut-off rules linked to mass and energy are also limited if the scope of the study is to assess toxicity and ecotoxicity indicators. Some raw materials, such as paints, may have a low energy or mass input while having a high toxicity effect. In this case they should be taken into account in the LCI of the building product. In current PCRs (e.g. the French PCR NF P01-010 standard), these substances are identified – e.g. in France as very toxic (T+), toxic (T), noxious (Xn), or dangerous (N) – and should be included in the inventory if there is an LCI available; otherwise they should be included in the methodological report.

 

2) Specific guidance for the cut-off rules for complete LCA of buildings

There is a difference in terms of cut-off rules between product LCA and building LCA. For product LCA, the cut-off rules are generally defined in an existing PCR, e.g. EN 15804 (see the  ‘Rules from’ section), or in the database. For building LCA studies the practitioner is likely to use already calculated LCA or EPD data. These data have already a cut-off rule linked to the product LCA studies (see the guidance above). At the building level, there is an additional layer of cut-off rules, which correspond to the number of building products quantified to model the full building.

EN 15978 states that the total excluded materials and processes should not exceed 5% of total energy use and mass. However, the cut-off should be used differently between screening, simplified and complete LCAs. The mass of the building is driven mainly by the structural components which can lead some products such as floor coverings being neglected. However, these are likely to have higher environmental impacts than the structural components for some specific impact categories. Therefore the cut-off rules should be extended in complete LCA to account for ILCD provisions.

The provisions in EN 15978 are somewhere in between a simplified and a complete LCA for the cut-off rules aspect.

 

3) Specific guidance for the cut-off rules for screening and simplified LCA of buildings

For building LCA, it is important to ease the process of doing an LCA study, as it is a time-consuming task to account of possibly hundreds of building products.

In the EeBGuide, the cut-off rules for screening and simplified LCA are less strict than for complete LCA, as some building products or technical equipment may not have LCA or EPD data in some countries.

In the current version of the EeBGuide these may be neglected, owing to potentially missing data, although the general rule for simplification would be to conduct a complete LCA, and then see whether  it is relevant to neglect these items (see 2.4 Study types). In any case, the limitation of building products to include should always be justified by the practitioner.

As an alternative for optional building products, it is also recommended that default values be used for these optional building products, as far as possible (see 2.4 Study types), as there are likely to exist in Europe, even if they are not very representative of a specific product. This enables the cut-off rules to be limited, even for screening or simplified LCA (validation step), while easing the completion of the study by practitioners through the use of default values.