Every LCA study generally follows ISO 14040 and ISO 14044, which provide general rules on how to conduct an LCA study – independent of the scope of assessment, type of product or associated industrial sector. They define the separate phases for such studies, and provide general rules for the application of this methodology. The defined phases are:
- Goal and scope definition.
- Life cycle inventory analysis (LCI).
- Life cycle impact assessment (LCIA).
Figure 7: Life cycle assessment framework according to ISO 14040/ ISO 14044
For LCA studies in the field of energy-efficient buildings, this approach is generally maintained. It is specified in more detail both in the ILCD Handbook and in CEN’s standards EN 15804 and EN 15978. Detailed descriptions of the steps that need to be addressed, following ISO 14040/14044, are defined in this guidance document.
The individual work items per step may vary, but to ensure that a study meets the basic requirements for LCA studies, every step has to be taken. So, for instance, the ISO 14040/14044 standards assume an LCA procedure that links elementary and intermediate flows (mass and energy flows that enter or leave a product system, e.g. as emissions to air) to unit processes. The development of the product model and the compilation of all these elementary flows take place during the life cycle inventory (LCI) step. If, as is frequently found in the construction sector, especially with EPD data, LCA data are provided using impact category indicators instead of elementary flows, the selection of environmental impact categories (to be defined within the ‘Goal and scope definition’ step), the life cycle inventory and life cycle impact assessment (LCIA) steps may already be completed by the data provider. The actual indicators evaluated in a study are therefore necessarily restricted, based on the available indicators listed for the data provided. In this context, it should be noted that, following EN 15804 and EN 15978, the LCIA steps are expected to be the responsibility of data providers (of background data or of specific EPD data).
So, if the LCA practitioner uses this kind of information source (i.e. EPD or LCA impact results), special care should be applied to ensure consistency between the calculations already made by data providers and those to be made by the practitioner. In particular, matching of the list of materials and quantities, often provided by the architect or construction company with the datasets available in the LCA database used, requires careful attention, and is frequently a challenge for the LCA practitioner. In addition, the use of EPD or LCA impact results should ensure that the same rules for LCI and characterization factors have been followed.
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
- 3.3 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