## 4 Results and Discussion
### Identification of Gaps Related to the Integration of EPD Data in IFC
The most widely applied and used property type is _IfcPropertySingleValue_, which defines a property with a single value. _IfcPropertyEnumeratedValue_ defines a list of predefined classes, _IfcPropertyBoundedValue_ defines the data range, _IfcPropertyListValue_ is intended for multiple ordered values, _IfcPropertyReferenceValue_ assigns a value to the property set through a link with predefined complex properties and _IfcPropertyTableValue_ defines one or many ranges of values (see Table 5). The _IFCPropertyAbstraction_ and the relation with other entities are defined on buildingS-MART documentation in the diagram for entity inference of the _IfcPropertySingleValue_[49]. For each impact category defined in IFC, a specific element can be included to store the link to the calculation method, including the reference to the relevant ISO, IEC or CEN/CENELEC standard. They can be referenced with a unique identifier, such as the work item (WI) code. For example, the WI code for EN 15804:2012+A2:2019 is 00350032. The same IFC element can be used for other documents, e.g., the IPCC methodology with its dated version. Existing IFC elements can be used for this purpose, such as _IfcExternalReference_ or _IfcDocumentReference_. It can be defined as a complex element, allowing the identification of documents using different codification, such as the digital object identifier (DOI) defined in ISO 26324:2025 [50]. _PsetEnvironmentallpactIndictators_ can refer to the relevant lifecycle module using the element _LifeCyclePhase_. However, the enumerated values included in IFC 4.3 do not cover all the information modules defined in the EPD standards (see gap 7). Table 6 below lists the _PEnum_LifeCyclePhase_ with reference to the information modules in current EN 15804 and in the future standard EN 15978, which should be published in December 2025. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Indicator** & **Name** & **Unit** & **Description** \\ \hline IFC ADPE & N/A 2 & & \\ \hline EPD ADPF & \begin{tabular}{l} Abiotic depletion potential for \\ fossil resources \\ \end{tabular} & MJ & \begin{tabular}{l} Abiotic resource depletion \\ (ADP fossil). \\ \end{tabular} \\ \hline IFC ADPF & N/A 2 & & \\ \hline \multirow{3}{*}{\
\begin{tabular}{l} EPD WDP \\ water consumption \\ \end{tabular} } & Water (user) deprivation potential, & & \\  & deprivation-weighted & m3 &
\begin{tabular}{l} AWARE 100 (Available \\ water Remaining). \\ \end{tabular} \\ \cline{1-1} \cline{2-4} IFC WDP & N/A 2 & & \\ \hline \hline \end{tabular}  
* Considering that _ClimateChangePerUnit_ refers to the total GWP, unclear in IFC 4.3. 2 Not available. 3 EN 15804+A2 refers to NMVOC, also including non-reactive VOC.  
\end{table} 
Table 4: _Cont._ \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**EN 15804:2012+A2:2019** & \multicolumn{2}{c}{**EN 17472:2022 and EN 15978:2025 1**} & \multicolumn{2}{c}{**PEnum_LifeCyclePhase in IFC 4.3**} \\ \hline \hline \multirow{4}{*}{Not defined in EN 15804+A2} & \multirow{4}{*}{A0 Pre-construction stage} & \multicolumn{2}{c}{Part of the processes included in A0 can be assigned to ACQUISITION and PROCUREMENT. However, a dedicated phase must be defined} \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \hline A1 Raw material supply, including processing of secondary material input 2 & As in EN 15804+A2 2 & Not defined \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \cline{2-2}  & & & \\ \hline A2: Transport of raw material and secondary material to the factory 2 & As in EN 15804+A2 2 & Not defined \\ \cline{2-2}  & & & \\ \hline A3 Manufacture of the construction products 2 & As in EN 15804+A2 2 & \multicolumn{2}{c}{MANUFACTURE or PRODUCTION. A specific element should be defined to avoid ambiguity} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Relationship between the _LifeCyclePhase_ element in IFC 4.3 and the information modules in CEN/TC 350 standards.