G-35 (Buildings) / G-33 (Products) Normalization of indicators

Aspect G-35 (Buildings) / G-33 (Products) Normalization of indicators
According to the ILCD Handbook, the normalization step refers to the expression of indicators (LCIA, midpoints or endpoints) relative to a common reference by dividing the indicator results by the respective reference value. Different normalization factors can be applied in practice to help the interpretation of results in the building sector. How can this issue be considered within this guidance document?

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 normalization of indicators (which are the LCA results of products and buildings) should remain an optional stage, according to ISO 14044. However, in certain circumstances the normalization of results may be very helpful for the LCA practitioner and/or the decision-maker, and assist interpretation of the study results. 
Rules from:
“Provisions: 6.7 Preparing the basis for the impact assessment […]

Normalisation and weighting: […]

XIII) MAY – Results interpretation: Normalisation and weighting are in addition optional steps under ISO 14044:2006 that are recommended to support the results interpretation (see part 6.3.6)”

Provisions: 10.3 Three levels of reporting requirements […]
IV) SHALL – Main report, with the following aspects […]

IV.e) Life cycle impact assessment results calculation, where applicable: […]

IV.e.vi) data and indicator results reached prior to any normalization, grouping or weighting shall be made available together with the normalized, grouped or weighted results.

IV.e) Life cycle interpretation: […]

IV.f.iv) full transparency in terms of value choices, rationales and expert judgements.

If the normalization step is considered for product or building LCA case studies it should be carried out in line with the ILCD Handbook. The assumptions should be documented as transparently as possible. Two types of normalization of results can be used in practice, answering two types of objective:1) Help to identify the most relevant indicators among the global set of indicators
In this case, the LCA results are scaled to a common geographical reference (e.g. at the European level, or in some national contexts) and for a given time period (e.g. 1 year). Generally speaking, normalization factors are available at the world, European and national levels per indicator per year. Doing this will enable the practitioner to identify the key indicators that are driven by the building sector, and in the specific study. It is a way to identify hotspots, and reduce for example the number of indicators from EN 15804/EN15978 or other indicators available in the ILCD Handbook (if relevant). The main issue is to be able to obtain the normalization factors for each indicator. The LCIA method usually provides normalization factors for the midpoint, such as the global warming potential (GWP), or endpoint indicators.For example, the CML 2002 method provides normalization factors for The Netherlands (1997), Western Europe (1995) and the world (1995). Other impact assessment methods, such as Eco-indicator 99, IMPACT 2002 and ReCiPe, also provide normalization values.

Some of these LCIA methods may be used in a building LCA in addition to the baseline indicators given in the EN 15978/EN 15804 standards. Previous European projects have provided the values for these normalization factors through their online deliverables.

Examples of normalization factors that can be used for the French context (mean impacts per person and per year) can be found below:

Mid-pointindicators Unit equiv-person /year Source
GWP kg eq-CO2 8680 CITEPA
AP kg eq-SO2 62.3 CITEPA
POCP kg eq-C2H4 19.7 CITEPA
EP kg eq-PO43- 38.1 IFEN
Other indicators Unit eq-person Source

Primary energy demand

MJ 48 670 Observatoire de l’énergie

Water consumption

m3 339 IFEN

radioactive waste

dm3 0.51 ANDRA

Other wastes

kg-eq 10400 ADEME

[Peuportier 2008]

Example of normalization factors that can be used for the European context can be found in the BRE Environmental Profiles Methodology.

A comprehensive set of normalization factors are described in detail in LoRe-LCA.

2) Comparison of LCA results with existing benchmarks

In the building sector, practitioners may be asked to comply with a set of targets for overall environmental performance. For example, an architect or a real estate manager may need to answer the following question: “Does the studied building perform well compared with current best and good practice?” In this particular case, the LCA results can be normalized to existing reference values to compare design alternatives with current practice.

Appendix B provides some first reference values for buildings for Germany and France.

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