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G-39 (Buildings) / G-37 (Products) Scenario analysis

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Aspect G-39 (Buildings) / G-37 (Products) Scenario analysis
Description
 Scenario analyses usually refer to future conditions that cannot be fully known by the time the LCA study is conducted. However, the uses of scenarios can meet different goals. Scenarios can look backwards or forwards, and can be linked to different applications. For example, a product is likely to be handed differently in each building. In this context, the use of scenarios may be very helpful in provide complementary results.Within this guidance document, is a scenario analysis necessary? How and when can it be conducted, depending on the study type?

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 building products screening LCA simplified LCA complete LCA
Provisions Scenario analyses may be conducted if relevant for the goal and scope of the study. They should be conducted for individual assumptions and choices in order to explain the impacts of such choices. For these cases, a scenario analysis should be conducted against the baseline scenario (see Chapter 2).
Rules from:
 EN 15804
7.3 Scenarios and technical informationILCD:
Provisions: 9.3.3 Sensitivity check (of accuracy and precision)
Guidance
 A scenario is addressed for each life cycle stage in EN 15804 and EN 15978. However, in addition to the chosen scenario for each life cycle stage it may be useful to assess alternative scenarios.A scenario analysis is closely related to a sensitivity analysis for key parameters. For example, in a scenario analysis, the practitioner may need to look at different building alternatives or reference study periods. The different aspects to consider for the scenario analysis depend on the goal and scope of the study. For example, the scenario analysis can be predictive (forecast, what-if), explorative (external or strategic) or normative (preserving or transforming) [LoRe-LCA 2011].

1) Guidance for building LCA studies

Different aspects can be considered for a scenario analysis, such as the reference study period of a building, the service life of building products, renovation scenarios, energy demand during the use phase, and user behaviour. For more information about scenario analyses for building LCA, please consult the LoRe-LCA report ‘Report on scenario for LCA in constructions’, available online.

2) Guidance for product LCA studies

For product LCA, scenario analysis can be done e.g. for an EPD that is likely to have different impacts in the implementation and use phases. Examples of such products include floor coverings. Having different scenarios enables the building practitioner to select the more appropriate scenarios for the building LCA case study.

3) Specific guidance in EeBGuide reporting templates

Scenario analyses are part of the reporting template for products and buildings case studies. In addition to the baseline scenario, the LCA practitioner is invited to conduct scenario analysis on a relevant set of parameters.

G-40 (Buildings) / G-38 (Products) Communication of LCA results

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Aspect G-40 (Buildings) / G-38 (Products) Communication of LCA results
Description
 The external and internal communication of LCA results is still error-prone. How should results be communicated? How should they be presented with regard to different experience levels of the audience?

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 building products screening LCA simplified LCA complete LCA
Provisions Especially for complete LCA studies, the documentation should be in line with ISO 14044, EN 15804 and EN 15978. The EeBGuide provides reporting templates for building and product LCA that are generally in line with these standards. These reporting templates should be used.EN 15978 describes possibilities for easier communication of the LCA results.
Rules from:
 EN 15978:
12.6 Communication of assessment results
12 Reporting of the assessment of resultsEN 15804:
8 Project report

EN 15942:
Reporting template for EPDs

ILCD:
15.4 Misleading reporting and communication
Guidance
 Requirements concerning reporting are part of the study type definitions. The reporting templates cover these rules.Special requirements for external reports and comparative assertions are given in ISO 14044. In addition, EPD programmes may ask for specific reporting requirements.ISO 14025 (and thus EN 15804) for EPD requires that the independent verifier generate a report documenting the verification process, while adhering to the obligations of the standard regarding data confidentiality. This report should be available to any person upon request.

G-41 (Buildings) / G-39 (Products) Reproducibility

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Aspect G-41 (Buildings) / G-39 (Products) Reproducibility
Description
 Reproducibility is an important aspect of the reporting step in life cycle assessment. According to ISO 14044 and the ILCD Handbook, it is characterized by providing comprehensive documentation on data, assumptions, calculation rules etc. that would allow an independent reviewer to adequately reproduce the results and the corresponding interpretation of any LCI and LCA study. Because of different data sources and confidential datasets, reproducibility may sometimes be difficult to achieve. In addition, the use of LCA in the building sector leads to the development of LCA software that may use different data, assumptions and calculation rules for a national context. How can reproducibility of LCA studies in the building sector be ensured without excessively increasing the time needed to complete a study?

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 building products screening LCA simplified LCA complete LCA
Provisions The description of all aspects related to the LCA study should be as transparent as possible.For confidential data, the assumptions should be made available to the independent critical reviewer (if relevant for the review process).For building LCA studies, the documentation may not be required at the same level of detail as for other LCA studies, owing to the use of predefined data or models (e.g. aggregated generic or EPD datasets with only impact indicators).
Rules from:
 EN 15978:
13 Verification of results

EN 15804:
9 Verification and validity of an EPD

ILCD:
Provisions: 6.2.2 Reproducibility

I) SHALL – Documentation for reproducibility

II) MAY – Accompanying documentation process

III) SHALL – Confidential information

Provisions: 10.2 Reporting principles

I) SHALL – Reproducibility and target audience to guide reporting
Guidance
 1) General guidance for ensuring reproducibility of product and building LCA studies
The ILCD Handbook provides detailed guidance on reporting. To ensure the best reproducibility of results, detailed reporting should be provided. This is especially true for aspirations concerning the quality of complete LCA studies. So, for instance, the author(s) of a complete LCA study should review whether the documentation using the EeBGuide reporting templates provided is sufficient to allow third parties to reproduce their study. If not, the practitioner should extend the documentation by considering the ILCD LCA report template and LCI reference dataset format.

2) Specific guidance for confidential product or building LCA studies
It is not always possible to make all the assumptions available to the public, e.g. for a comparative LCA study of two structural systems, owing to confidential industry data. According to the ILCD Handbook, there is a need to balance reproducibility and confidentiality. In general, an independent external reviewer (e.g. for an LCA study) or verifier (e.g. for EPD) is a sound option to ensure that the results of comparative LCA studies (disclosed to the public) are reproducible. In this special case, the confidential data are made available only to the reviewer for e.g. raw data or unit process data in the case of a product LCA.

3) Specific guidance for building LCA studies

The LCA methodology cannot be applied with the same level of detail for building LCA studies. Various simplifications are applied, e.g. by using only LCIA indicators instead of full LCI or unit processes. In this context, reproducibility remains as important as for product LCA. It is very important in a national context, when e.g. several LCA software tools exist on the market. Possible ways of achieving reproducibility for building LCA studies include:

– harmonization of physical building description data (see the corresponding aspect);

– choice of a common national set of generic LCA data (that can be used for early design stages).

In addition, some specific requirements are needed for each LCA software:

– Provide dedicated user manuals.

– Document, in a transparent way, the assumptions of the LCA software (data, calculation rules, expression of results).

– Facilitate data selection with e.g. a predefined building description.

Reproducibility can be assessed in various ways. For example, training tests can assess the reproducibility among different LCA practitioners using the same LCA software and case study. Here, the influence of the practitioner is being assessed. Conversely, the same LCA practitioner can model the same case study using two different building LCA software tools. Here, the databases and methodological assumptions of the software are being assessed.

One important aspect of reproducibility is the use of common datasets. Unfortunately, in some national contexts, different databases (e.g. generic and EPD data) can be used, answering different goals. In this specific case, data analysis tools may need to be developed to assess the differences in LCA data on building products and processes, in addition to the reproducibility tests explained above. Some guidelines on this topic, and on implementation in the French context, can be found in [Lasvaux 2011].

G-42 (Buildings) / G-40 (Products) Life cycle inventory documentation

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Aspect G-42 (Buildings) / G-40 (Products) Life cycle inventory documentation
Description
 In order to fulfil the reproducibility requirement of a project, documentation of life cycle inventory datasets is very important. What level of detail makes sense?

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 building products screening LCA simplified LCA complete LCA
Provisions If no inventory documentation is asked for, it is sufficient just to name the methodology applied. If documentation is mandatory, use of the format mentioned in the ILCD Handbook is recommended as a minimum, including compliance with the nomenclature of the ILCD reference elementary flow list.
Rules from:
 ILCD:

Compliance rules and entry-level requirements

Provisions: 7.4.5 Naming and other conventions“I) SHALL – Elementary flows

I.a) Use ILCD reference elementary flows […]

I.c) Use ILCD elementary flow categories […]”
Guidance
 This point is subject to ongoing discussion, and will need to be revised in future.In the construction sector, building-level LCA studies are frequently conducted solely on the basis of impact indicator datasets for products, for example from EPDs or LCIA databases. In such cases, the life cycle inventory cannot be documented by the practitioner, and hence this aspect does not apply.For some selected data, simplified rules for the inventory analysis (e.g. a minimal list of substances) may be defined. However, a high level of accuracy should be ensured by checking a complete LCI against a reduced LCI for the same building material. This recommendation was part of a previous European project (LoRe-LCA) report ‘Building LCA good practice report’, available online. Examples of studies assessing the relevance of a complete list of elementary flows according to the chosen impact category can be found e.g. in [Lasvaux 2012].

It may be appropriate, for example, to list all inventory flows that are responsible for more than 1% of impact in any category.  ISO 14044 4.4.2.5 suggests it may also be appropriate to list separately all inventory flows that do not contribute to any impact category: this can highlight errors in the classification and characterisation processes of LCIA. 

G-43 Documentation of LCA results

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Aspect G-43 Documentation of LCA results
Description
 Each LCA study has to be documented by means of an LCA report to demonstrate compliance with existing LCA standards (e.g. [ISO 14040], [ISO 14044] or [EN 15804], [EN 15978]). The hypotheses, methodological choices and LCA results are reported. However, how can be such a report be structured/documented for any LCA study for buildings? What is the important information to give in the report?

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 building products screening LCA simplified LCA complete LCA
Provisions The documentation of LCA results should be in line with ISO 14044; different templates should be used according to the level of complexity of the analysis (screening, simplified or complete).
Rules from:
 EN 15978:
12. Reporting of the assessment of results
12.1 General information on the assessment
12.2 General information on the object of assessment

12.3 Statement of boundaries and scenarios used in the assessment

12.4 Data sources

12.5 List of indicators used for assessment and expression of results

12.6 Communication of assessment results”

ISO 14044:

5 Reporting

ILCD:

10 Reporting (General Guide for Life Cycle Assessment)
Guidance
 The ISO 14044, ILCD and EN 15978 provisions should always be respected. The template defined for each study type (screening, simplified and complete) within the EeBGuide project should be used according to the goal and scope of the study.

The template for case studies can be filled in by reporting information from the building project, and by identifying any deviation from the EeBGuide recommendations (e.g. for LCA data and methodology).

G-44 (Buildings) / G-41 (Products) Critical review

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Aspect G-44 (Buildings) / G-41 (Products) Critical review
Description
 A critical review may be needed, especially if comparative results are intended to be disclosed to the public.How should this aspect be considered for building and product 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 building products screening LCA simplified LCA complete LCA
Provisions The critical review (or verification if it concerns an EPD) should be in line with the ILCD Handbook, and with ISO 14040/14044, as well as  with ISO 14025 (for verification of EPD).The EeBGuide provides a review template that can be used to review an LCA study conducted according to the EeBGuide provisions. In this case, the review provisions supersede the ILCD and ISO 1404 ones.
Rules from:
 EN 15978:

12. Reporting of the assessment of results

ISO 14044:

5 Reporting

ILCD:

Provisions: 11 Critical review

I) SHALL – See Chapter 6.11 for key decisions made on the critical  review

II) SHALL – Review scope, methods, and documentation
Guidance
 The needs of a critical review depend on the goal of the study (stand-alone LCA vs. comparative assertions).Please note that within the context of EPD, the word to use is ‘verification’. In that context, it is likely that national EPD programmes will provide checklists of aspects to check for EPD conformity.In other cases, a critical review may be needed. The time and efforts required depend on the goal of the study.The EeBGuide provide a simplified review checklist that can support compliance with the EeBGuide provisions for building and product LCA studies.

6.1. Overview

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This chapter addresses aspects that are related to life cycle stage A. They provide provisions, rules and guidance for the goal and scope definition and the inventory analysis steps according to [ISO 14040] and [ISO 14044]. The following list describes the aspects addressed in Module A.

6      Aspects concerning Module A – Product and Construction Process stage

  • 6.1.  Overview
  • 6.4  Module A5 – Construction installation process

 

A-01 Use and adaptation of available cradle-to-gate and cradle-to-grave LCA or EPD data for building products and technical equipment

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Aspect A-01 Use and adaptation of available cradle-to-gate and cradle-to-grave LCA or EPD data for building products and technical equipment
Description
 Different LCA data describing the impacts of raw materials supply, transport and manufacturing (cradle-to-gate data) can be used in practice, depending on the goal and scope, on their availabilities in LCA or EPD databases, and on the geographical location of the building. In addition, they need to be adapted, e.g. information for the gate-to-grave impacts, or adaptation of the cradle-to-gate data to a different context.Which LCA or EPD data should be used in a building LCA study? How can they be adapted if they are not fully appropriate?

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 use existing LCA or EPD databases for selecting cradle-to-gate data or cradle-to-grave data. As far as possible, the practitioner should use a single database for deriving all the data on building products and technical equipment, or otherwise make sure that the building products and technical equipment data are based on identical assumptions.The adaptation of cradle-to-gate data should use consistent rules for building LCA modelling.
Rules from:
 EN 15978:10.2.2 Adaptation of cradle to gate (product stage) information

10.2.3 Adaptation from gate to grave information (Modules A4 to C4) and Module D
Guidance
 The choice of LCI/LCIA datasets depends on the goal and scope of the study. Please refer to the corresponding general aspects (in the inventory analysis section). The existing LCA data should be handled with care, as they may have different system boundaries. They also can be used in different contexts, which means they will need to be adapted.1) Guidance for the use of existing databases on building products or technical equipment

Generally speaking, the use of a single database is highly recommended when conducting a building LCA study, so as not to bias the results (e.g. in comparative assertions). Existing LCA or EPD databases are often not comparable, owing to differences in assumptions and methodologies.

However, some data (e.g. for technical equipment) may not have been calculated using the same rules (or the same PCR) as other data (e.g. building products). The use of two different databases can be justified in this case if the main conclusions of the study are not affected by the use of data coming from different sources. Alternatively, the practitioner may prefer to rely on a single database, even if not all the building products and technical equipment have corresponding LCI/LCIA data.

2) Adaptation of cradle-to-gate data for a building LCA study

The cradle-to-gate data can be adapted either for the production stage (e.g. French or German cradle-to-gate data used in a neighbouring country) or for the additional life cycle stages (Modules A4, A5, C and D).

Sometimes data are already presented as cradle-to-gate data: for example, the French EPD database (INIES) provides for some EPD cradle-to-grave results without information for the cradle-to-grave stage. In this case, the practitioner should carefully check whether the scenario and the boundaries for the gate-to-grave stages are relevant for the goal and scope of the study (e.g. according to EN 15804).

3) Use of scenarios for gate-to-grave data for a building LCA study

Scenarios are needed to assess the cradle-to-grave impacts depending on the goal and scope of the study (please refer to the corresponding aspects in every life cycle stages for each study type).

Even if cradle-to-grave data are available (e.g. French EPD for building products), the scenarios included in these data should be checked for consistency with the scenarios representative of the building under study.

If the EPD is broken down into different life cycle stages, the practitioner can then select the cradle-to-gate EPD information and adapt the gate-to-grave information.

Scenarios for gate-to-grave impacts need to use default values (or else specific values) especially for:

Modules A4 and A5:

  • the transportation distance from the factory to the building site (in km);
  • the LCA data for transportation processes (e.g. lorry, train);
  • the construction losses of building product (in %).

Module B – Use stage:

–       the reference service life of the product (in years);

–       other aspects (if relevant).

Module C – End-of-life stage

–       the share of end-of-life scenarios i.e. landfill, recycling, incineration (w/o heat recovery) for each type of building material;

–       the corresponding LCA data.

Module D – Benefits and loads beyond the system boundary

–       the share of reuse, recovery and recycling potential for each type of building material.

–       the corresponding LCA data

Guidance for each module (and corresponding parameters) can be found in the corresponding chapter (Modules A, B, C and D); if not, he practitioner can use the scenarios proposed in building LCA tools (such as EQUER or ELODIE in France), or in building certification schemes.