Simon Corbey (Director, ASBP) and Flavie Lowres (LCA Expert, ASBP) with thanks to Elodie Mace at CSTB in Paris
We have asked how dynamic LCA (life cycle analysis) was adopted into the French system and it is not clear. Feedback states it was adopted at ministerial level, without consideration of expert recommendations.
Static LCA is still allowed, but as dynamic LCA seems to give better results for every type of material, everybody will tend to choose the dynamic version.
The description of the methodology is provided in this document (see page 51 onwards):
Here is our understanding of the methodology:
The approach seems very similar to EN15978 (although it is not mentioned). You have to report results for the following phases: production phase (same as A1 to A3), construction phase (same as A and A5), use phase (B1-B5, B6 (energy in use) and B7 (water in use), end of life (C1-C4) and D.
For each life cycle phase, the method requires that all impact associated with the following categories are taken into consideration:
- Components (composant): construction products and mechanical and electrical systems
- Energy (energie): operational
- Water (eau): operational
- Site (chantier): energy and water consumption on site and all wastes, including water
- Parcel: all components not necessary to the construction of the building, but it could include fences, infrastructure, etc
The system boundary of the study are illustrated below:
It is advised to use LCA tools that have been tested to ensure they are compliant (eg: OneClickLCA).
Results are expressed against 27 environmental impacts. Data is available via the INIES database (http://inies.fr/acceuil/).
The calculation method is illustrated below:
Translated in English:
Facteur d’adaptation (renouvellements du composant, pondération) = Factor of adaptation (component replacement, weighting)
This factor may be link to the service life of the product, a dynamic weighting or adaptation of the quantity to meet the functional requirement (eg: to translate from kg to m2), etc.
Quantities = Quantity
Données environmentales = Environmental data (eg : kgCO2eq)
The final result of the impact of the building is the sum of the impact that happens through 4 of the 5 categories listed above (component, energy, water, site) – see: illustration 13 below:
The energy calculations should be done over 50 years.
The use of dynamic LCA (pages 58-59) is encouraged. The dynamic approach applies weighting factors depending on when the impact will happen and therefore puts a heavier weight on impact generated now versus those created in the future. For products for which the emissions are mainly taking place during manufacturing (eg: concrete, steel), then the static and dynamic approaches are similar. The dynamic approach seems to benefit products such as timber that will have a low impact “now” (due to sequestrated carbon) and have a heavier impact in the future (compared to concrete and steel).
The following example is provided:
|LCA phase||kgCO2eq||LCA phase||kgCO2eq|
|Manufacturing||-600||Year 0, weighting of 1 x -600||-600|
|Construction||30||Year 0, weighting = 1 X 30||30|
|Use||0||Year 1 to 49, weighting = 0.984 to 0.587 x 0||0|
|End of life||700||Year 50, weighting 0.578 x 700||404.6|
The weightings are provided in the following diagram:
This article explains the difference in results of static versus dynamic: ACV dynamique vs ACV statique (2/3) : étude de cas pour des logements collectifs (construction21.org). Examples of performances of different types of buildings are provided. Results using a static approach comparing a CLT and a concrete building:
The example also shows the results of the study using the E+C- and the RE2020 approaches.
Below are the results of the same study but using a dynamic LCA approach:
These examples seem to suggest that the dynamic approach is beneficial for both types of systems, but perhaps better for the CLT. This is summarised in the graph below which shows the difference between the CLT and the concrete results for the different approaches:
For any queries about this blog post, please contact Simon Corbey – email@example.com.