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François et al. Carbon Footprints 2026, 5, 22 Page 19 of 22

Concerning additional information, compared to a static LCA, apart from the chronological details of GHG
emissions in the inventory, no additional data is required: the tool determines the LCD value directly from
the inventory, the user knows and can easily enter the THI value. However, the tool is evolutive and new
physicochemical parameters from newer studies or reports (e.g. IPPC reports) can be updated and taken into
account (radiative efficiencies, half-lives, equilibrium equations for CO and methane degradation). In that
2
case users can easily update the tool by changing these data themselves. Values of lifetimes of all GHGs are
provided in the “IPCC AR6” sheet, and b and τ are provided in the “Additional data” spreadsheet of the
n
n
worksheet-based tool .
[22]
The fact that the integration period is defined based on the product’s life cycle can pose problems in terms of
application. First, a producer may want to propose deliberately long lifespans in order to reduce its impact, as
shown in Figure 3. Although feasible, this limitation is also present in the current method , which, in
[11]
addition to being incompatible between static and dynamic indicators, assigns zero impact to all emissions
occurring beyond 100 years. Secondly, it could be argued that it is difficult to compare products with
different lifespans, which are uncertain in the building sector since products have long lifespans. This is
entirely true, but this difficulty, which is inherent in the need to compare on the basis of identical functional
units in standards in general, arises for all dynamic methods. It has been resolved by the RE2020
regulation , which imposes an identical lifespan on all buildings, and it has been resolved in EPDs in
[11]
general, where manufacturers’ consortia define typical usage scenarios, including lifespans, using Product
Category Rules .
[35]

Should regulation be changed?
The simple case study presented in this article shows the influence on the results when non-respecting the
compatibility criterion between static and dynamic indicators, and the actual RE2020 regulation
overestimates benefit on GWP100 reduction obtained by delaying emissions. Furthermore, this benefit is
even emphasized by not introducing distinct factors corresponding to distinct GHGs. This difference is
substantial, as illustrated by the case study.

Experimental analysis has shown that an approximate relationship can be established between static and
dynamic characterization factors for the GWP indicator . However, this relationship was derived from
[15]
dynamic indicators obtained with the RE2020 method and is therefore not applicable in the context of the
present work, as it relies on a partial dynamic approach that does not satisfy the compatibility condition
demonstrated in this article and formalized in Equation 14.

Furthermore, the mathematical condition ensuring compatibility between static and dynamic approaches,
expressed in Equation 14, is related to a previous discussion , although that previous work did not explicitly
[29]
mention that this relationship only holds when compatibility between static and dynamic approaches is
required. The developed method in this article corrects these shortcomings and, as illustrated in the case
study, can be readily applied by practitioners. Updating current regulations accordingly would therefore
provide a representation that is more consistent with the physical effect of delaying emissions. More broadly,
regulations and climate assessments should incorporate metrics that do not depend on times horizons or a
reference gas. In parallel, IPCC must present and further develop these metrics and their associated
characterization factors within its scientific reports.

CONCLUSIONS
Climate change assessment in dynamic LCA improves the accuracy of LCA results but requires rigorous
definition, particularly when dynamic indicators are derived from static approaches such as reference-gas
impulse emissions. In this regard, the present article introduces two delay factors associated with GWP and