## 4 Results and Discussion
### Identification of Gaps Related to the Integration of EPD Data in IFC

Table 6: _Cont._LifeCyclePhase_ values must include all CEN/TC 350 information modules. In order to store EPD data according to CEN/TC 350 standards (see gap 7), the following information modules should be added as enumerated values in \(PEnum\_LifeCyclePhase\): A0, A1, A2, A3, A1-A3, A4, A4.1, A4.2, A5.1, A5.2, A5.3, A5.4, B1, B1.1, B1.2, B6, B6.1, B6.2, B6.3, B7, B7.1, B7.2, B7.3, B7.4, B8, B8.1, B8.2, C2, C3, D, D1, D1.1, D1.2, D1.3, D1.4 and D2. The following modules have some correspondence with IFC (see Table 6 above): AS INSTALLATION, B2 MAINTENANCE, B3 REPAIR, B4 REPLACEMENT, B5 REFURBISHMENT, C1 DECONSTRUCTION and C4 DISPOSAL). However, it is recommended that some of these existing \(PEnum\_LifeCyclePhase\) be renamed to align with the terminology of ISO 21930 and EN 15804 (gap 17). BuildingSMART identified the need to incorporate some of the modules in 2022 [48], but it should be noted that the report does not consider the modules added by CEN/TC 350 after the publication of EN 15804+A2 and, in some cases, their names do not match the terminology of the European standards. [PERSON] et al. [51] explored the potential of a life cycle repository for environmental and economic analysis. It identified several EPD-related elements in the structure created for the information delivery manual (IDM) and the model view definition (MVD), such as 10 properties focused on the environmental impacts of its manufacture, 22 properties focused on transportation impacts and 26 properties focused on the waste treatment of materials. [PERSON] et al. also proposes the creation of a specific _IfcValue_ for each category, to better define the environmental characteristics. The main additional gaps related to IFC are analyzed in Table 7. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Gap** & **Name** & **Analysis** \\ \hline
15 & _Pset\_EnvironmentalImpactIndicators_ calculation method & The calculation methods are not generally defined (with a dated version). The document defining the calculation method can be defined with the DOI or, for standards, with the WI code. In some cases, the reference standard is superseded (e.g., ISO 21930:2007). The reference to _old_ methods should be maintained, to ensure compatibility, but new references should be added. It is a particular case of gap 12. \\ \hline
16 & Impact categories and indicators not defined in _Pset\_EnvironmentalImpactIndicators_ & It is essential that all properties and indicators from the core EPD standards are included. Incorporating new indicators into a revision of the official IFC schema will require careful consideration to ensure that the necessary changes can be made in a timely manner to keep pace with market demands. Therefore, new properties should be tentatively included based on a governance system or in repositories such as bSDD. \\ \hline
17 & Lack of alignment of life cycle stages & The element _LifeCyclePhase_ should be aligned with the core EPD standards (see gap 7 and Table 6). \\ \hline
18 & Adaptation of properties to the _concepts_ in the core EPD standards, including terminology & e.g., IFC uses _ClimateChange_ but the terminology of ISO 21930 and EN 15804 is GWP. \\ \hline
19 & Limitations of _IfcMeasureValue_ & There are units which are not supported natively by the current IFC schema. In addition, some units need to refer to specific elements, e.g., unit “mass” can refer to kg CO\_2 eq (GWP) or kg CFC-11 eq (ODP). \\ \hline
20 & & Elements in IFC can be multilayered or kits, aggregating data from several products. In addition, data transfer can result in the loss of information. Therefore, the URI of the original dEPD should be included in the BIM model. This option will ensure that the primary data is available for retrieval if needed, thereby avoiding an excessive loading of the model. \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Gaps specific to IFC.