By Bruno Peuportier (MINES ParisTech, PSL Research University, FR)
The longevity of buildings and lengthy roadmaps for a transition stretching to 2050 are misaligned with the urgency to act on the climate situation and the short mandates of elected officials. In this context, dealing with time is complex. Good practice needs to focus on acting and reporting during a shorter period (the electoral cycle) rather than postponing the progress to the next period. Three specific actions are recommended: (1) the need for clear actions, measurement and reporting; (2) policies and regulations must account for complexity and not result in merely shifting impacts; and (3) life cycle thinking.
Much can be learned from monitoring, at any geographic scale, and feedback helps improving road maps. Figure 1 shows the variation in measured heating energy consumption for 18 identical low energy houses in Germany according to the passive house label (Feist et al., 2005).
Measurement is essential to verify the real performance of completed buildings, which can deviate significantly from the calculations. Figure 1 shows that best practice is achieved on average in the case of this exemplary project, and that the actual energy bill significantly depends on occupants’ behaviour. This suggests that involvement of citizens is essential in the energy transition.
Long-lasting artefacts like buildings deserve careful design study, and this is especially true on a global policy scale. A global energy transition policy including consumption and production should be elaborated rather than promoting simplistic strategies. For instance, replacing all oil and gas boilers with electric heating is simplistic. This will create a very high peak demand in winter during which wind and solar production will be insufficient. Renewable gas (hydrogen or synthetic gas) can be produced when solar and wind resources are abundant, and stored to meet peak demand. Figure 2 shows the large uncertainty about the CO2 content of 1 kWh electricity consumed in France related to different energy transition scenarios and life cycle assessment (LCA) methods (Frapin and Peuportier, 2020). This evidence questions the systematic electrification promoted by some policy makers. GHG emissions may be higher for electric heating than for gas (being 270g CO2eq/kWh) using the GHG protocol (GHG-P) or marginal derivative (MD) LCA methods.
Life cycle assessment addresses not only greenhouse gases (GHG) emissions, but a set of indicators related to damage to human health, biodiversity and resources. The aim is to avoid impact shifting, e.g. replacing CO2 emissions with nuclear waste, risk and depletion of resources. This also adds complexity but it is essential for a truly responsible policy.
Another goal of lifecycle thinking is to avoid impact shifting over time. For instance, the forthcoming the French regulation imposes CO2 thresholds on products without accounting for their energy benefit during the use stage. The aim is to reduce GHG emissions during the manufacturing process. But this short-term approach disadvantages longer-term savings e.g. insulation and renewable energy systems. Such an approach will shift impacts to the use stage and therefore is inappropriate: whole lifecycle indicators should be used.
Discounting the impacts of future GHG emissions, as in so-called "simplified dynamic LCA", is also implemented in the French regulation. This creates a debt to future generations and disadvantages energy efficient techniques, as shown in Figure 3. When comparing double and triple glazing, a truly dynamic hourly LCA method (Roux et al., 2016), and an LCA with a fixed time horizon according to the French regulation lead to different results. Using an hourly dynamic LCA, triple glazing reduces GHG emissions by around 40 kg CO2eq/m2 of window over 50 years, whereas it is of no interest when discounting future emissions (LCA with fixed time horizon).
The choice of a simplistic assessment will yield different results – hourly dynamic LCA vs LCA with a fixed time horizon.
These examples show the influence that policies and regulation have on technological choices and actual outcomes. To be effective and enable robust progress towards a climate responsive built environment policies and regulation must address complexity and verify actual results. Approaches that are too simplistic are likely to merely shift the impacts. The creation of short-term goals and actions (to augment medium- and long-term goals) are vital to ensure that progress is made.
Frapin, M. et Peuportier, B. (2020). ACVs Energies – Livrable 5. Etudes de cas et Résultats obtenus. Paris: ADEME. https://librairie.ademe.fr/energies-renouvelables-reseaux-et-stockage/4447-acvs-energies-comparaison-d-approche-acv-des-systemes-energetiques.html
Bühring, A. and Kiefer, K. (2002). Monitoringbericht 2001 zum Förderprogramm Wärmeerzeugung im Passivhaus der EnBW Energie Baden-Württemberg AG. Freiburg: Fraunhofer-Institut für Solare Energiesysteme.
Feist, W., Schnieders J., Dorer V., Haas A. (2005), Re-inventing air heating: convenient and comfortable within the frame of the passive house concept. Energy and Buildings, 37 (11), 1186–1203.
Lab recherche environnement. (2021). L’analyse de cycle de vie dynamique décryptée par les chercheurs. https://www.lab-recherche-environnement.org/fr/article/lanalyse-de-cycle-de-vie-dynamique-decryptee-par-les-chercheurs/
Roux, C., Schalbart, P. and Peuportier, B. (2016). Accounting for temporal variation of electricity
production and consumption in the LCA of an energy-efficient house. Journal
of Cleaner Production, 113, 532-540. https://doi.org/10.1016/j.jclepro.2015.11.052
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