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Advancing Cost Estimation Through BIM Development: Focus on Energy-Related Data Associated with IFC Elements  
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consistent framework for structuring geometric, semantic, and cost-related data within BIM environments [4; 5]. However, its application in integrating energy analysis data with cost estimation for retrofitting projects remains limited. Existing cost estimation approaches do not systematically link material, installation, and operational energy costs within BIM, making it challenging to assess total cost trade-offs across retrofit scenarios [6; 7; 8]. Moreover, the absence of standardized workflows within IFC limits interdisciplinary data integration and scenario-based comparison [3; 9; 10]. Addressing these limitations requires an IFC-based methodology capable of structuring cost and energy data for more informed retrofit planning.  
This research aims to develop an IFC-integrated cost estimation framework that supports energy and material cost evaluation of energy and materials costs across multiple retrofit scenarios. The framework enhances the reliability of cost estimation and provides stakeholders with a structured approach to minimizing total cost in retrofit selection. The key contributions of this study include:  
* Cost Estimation Framework, a structured approach for integrating material, installation, and operational energy costs within IFC, enabling comparative evaluation of retrofit scenarios.
* IFC-Based Cost and Energy Data Integration, a methodology that enhances the structured representation and interoperability of cost estimation and energy analysis within the IFC framework.
* Optimized Retrofit Scenario Selection, a structured decision-support framework for identifying the most cost-effective retrofitting strategy based on total cost considerations.  
This research follows a three-phase methodology: (i) BIM Model Development--developing a structured IFC-based representation of an existing building with its geometric, material, and construction properties; (ii) Energy-Cost Data Integration--performing parametric energy simulations to evaluate retrofit scenarios while linking cost estimation data and energy analysis reports to IFC elements; (iii) Optimal Retrofit Scenario Identification--using a structured total cost (i.e., installation material and operational energy) assessment to select the most cost-effective and energy-efficient retrofitting solution.  
The novelty of this research lies in the integration of energy and cost data within the BIM-IFC framework, enabling a comprehensive cost estimation and evaluation of retrofit scenarios. The outcome of this study provides industry professionals and policymakers with a structured decision-making tool to maximize energy savings while ensuring cost-effectiveness. Consequently, besides visualizing the physical properties of a building, BIM becomes a multidimensional framework that supports structured decision-making by integrating sustainability, energy performance, and economic analysis.  
This paper is structured as follows: Section 2 presents the background and literature review on BIM-based cost estimation and IFC schema integration. Section 3 details the research methodology, including the BIM model development, energy simulation, and cost integration process. Section 4 describes the case study and implementation. Section 5 discusses the results and methodological implications. Finally, Section 6 provides the conclusions and outlines future research directions.