## 4 Results and Discussion
### Identification of Gaps Related to the Integration of EPD Data in IFC  
A fundamental distinction that limits the direct integration of EPD data into IFC is that the EPD contains more detailed or additional indicators than the current IFC schema (IFC 4.3.2.0 [30]) supports. This study assessed IFC 4.3 elements used to store EPD data and tested the integration of product environmental data into a BIM model (see Section 4.3), to analyze the effort required for human interpretation, validation and transfer of data. The primary mechanism for environmental data storage in IFC is _Pset_Environmental ImpactIndicators_, which defines properties for various impact indicators per a product's functional unit. Direct mapping of EPD and IFC parameters are currently used for some elements, such as:  
* Depletion potential of the stratospheric ozone layer (ODP) (in EPDs) with _StratsbericOzoneLayerDestructionPerInit_ (in IFC). \begin{table}
\begin{tabular}{p{42.7 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Gap** & **Name** & **Analysis** \\ \hline
12 & Unique identification of the test, calculation or assessment method for any property included, both performance characteristics and LCA-based indicators & The dated version of the method must be uniquely identified, using a single UID or a pair of UIDs (one for the property, e.g., GWP-total, and one for the dated version of the calculation method). However, this gap cannot be resolved solely by revising the IFC schema, as the UIDs must be common for different systems. Options to identify documents can be the DOI or, for standards, the WI code. WI 0442061 [11] will provide additional information on how to refer to the assessment method for European harmonized standards. & The dated version of the method must be uniquely identified, using a single UID or a pair of UIDs (one for the property, e.g., GWP-total, and one for the dated version of the calculation method). However, this gap cannot be resolved solely by revising the IFC schema, as the UIDs must be common for different systems. Options to identify documents can be the DOI or, for standards, the WI code. WI 0442061 [11] will provide additional information on how to refer to the assessment method for European harmonized standards. & Additional information on EPDs includes different types of data referring, for example, to an attribute of the product (e.g., compostable), a quantifiable property (e.g., 50\% recycled content) or information from the manufacturer (e.g., certified according to ISO 14001). The identification of common information should be made in the horizontal standard and, for properties applicable to the product family, in the PCR. Therefore, this gap cannot be resolved solely by revising the IFC schema. However, IFC can include elements to store this type of data. This information can also be retrieved from the source EPD, if the link is provided (see gap 20). & This gap requires further research in order to structure metadata using, when possible, parameters allowing machine interpretation. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Gaps related to results of the LCA and the product’s performance data. * Acidification potential (AP) (in EPDs) with _AtmosphericAcidificationPerUnit_ (in IFC). * Formation potential of tropospheric ozone (POCP) (in EPDs) with _PhotochemicalOzone-FormationPerUnit_ (in IFC). However, this mapping should be assessed with caution. Typically, IFC parameter descriptions offer only generic definitions, without referring to the calculation standards. The identification of the calculation method (gap 12) is required to evaluate the result, and its absence poses a significant challenge to the automated data integration process. When the reference is not provided, it is imperative that the data is assessed by a qualified expert to ensure that the model is populated with the appropriate information. The limited set of environmental parameters in _Pset_EnvironmentallImpactIndicators_ makes it so that a full EPD data import cannot be completed without the creation of custom attributes.