After selection of the study type and the subsequent filtering of aspects, the LCA study is set up according to general LCA practice, based on ISO 14040/14044. This process is briefly explained below with a generic template of how to set up an LCA study.
Step 1: Goal and scope definition
The definition of goal and scope relates mainly to the identification of study type and aspects considered for the LCA study, as described in section 3.2.1. Based on the goals of the study, and its intended application and audience, further specifications have to be made:
- The object of the assessment (e.g. building, or innovative technology) and its function (e.g. office use, or energy-producing façade collector).
- Definition of a functional equivalent – especially important for comparative assertions.
- System boundaries – the life cycle phases to be included, depending on the study type or guidance for applying cut-off rules (e.g. with regard to infrastructure and transport), should be specified.
- Procedure for allocation – several common allocation cases (e.g. for co-production, or reuse and recycling) with regard to mass, energy or environmental significance are required.
- Choice of environmental impact categories, indicators and characterization models used for the impact assessment.
- Data requirements and quality – the type of data to be used (e.g. generic or specific), data uncertainty, the use of foreground or background data (e.g. power mix) and specific data quality requirements for comparative assertions should be defined; missing data have to be documented.
- Source of the data (origin, representativeness) and producer/sponsor of the LCA should be documented.
- Assumptions and limitations – These may address, for example,. the set-up of specific scenarios for the use phase, the treatment of capital equipment or machinery within the production phase, or deviations from guidance provided within this document; a transparent documentation is required.
Examples and guidance on the above topics are provided within respective aspects of Section 5.2 ‘Goal and scope definition’ in this guide.
Step 2: Inventory analysis and product model
The method of data collection and the quantification of input and output flows (e.g. materials or energy) differ for screening, simplified and complete LCA studies, and depend both on the complexity of the product being assessed and on the assessed life cycle stages. The data sources used (e.g. publicly available or company/product-specific ones) and the quality of background data for the inventory analysis also have an influence on the impact assessment. Guidance on data collection, calculation, validation, and relating the information to e.g. life cycle stages or elements of the object of assessment. is provided in Section 5.3 on ‘Life cycle inventory analysis‘. Building and building product contributors that have to be considered are also defined. By using generic data or EPD as a data source for building LCAs, LCA practitioners typically do not need to perform the inventory analysis. Normally, therefore, none of the construction elements is individually modelled back to the elementary flows.
Step 3: Impact assessment
For quantifying potential environmental impacts, it is important to choose both environmentally relevant, technically and scientifically valid environmental indicators and the underlying characterization models for impact assessment. Environmental indicators and impact categories for which scientific consensus is not yet reached (e.g. water consumption, land-use change, toxicity and ecotoxicity or carbon sequestration) are addressed within Section 5.4 on ‘Life cycle impact assessment’.
Step 4: Interpretation and documentation
The interpretation of results serves, for example, to identify hot spots (e.g. distinct life cycle phases or elements of the object of assessment contributing to environmental impacts), and provides understanding of the sensitivity and uncertainty of the results. Requirements for and guidance on the use of normalization, grouping or weighting are provided in the sections on ‘Interpretation’. Cases where a sensitivity analysis is useful are also defined.
Step 5: Review
An external critical review is necessary for all comparative LCA studies, and for studies that are made publicly available. Guidance on simplifications for the review of stand-alone and screening LCA studies, and for studies within the E2B EI, is provided under the section ‘Reporting’ in Chapter 5 on ‘General aspects’.
Reporting and review templates are provided online at the official project website, and these are particularly helpful with step 1. They form the basis for documentation that is in line with the present guidance document, and which might be enhanced with further specific information if required or recommended (e.g. if future technologies and innovations are considered).
3 How to use this guidance document
- 3.1 Structure of the guidance document
- 3.2 How to conduct an LCA study within the field of energy-efficient buildings
- 3.2.1 How to start and proceed with an LCA study.
- 3.2.2 LCA study set-up: generic template.
- 3.3 Compliance with this guidance.
- 3.4 How to proceed with the service life assessment in building and product LCA studies
- 3.5 Further information and training materials