On Monday, 2 June 2025 the CTBUH Height & Data Committee convened for their second meeting of the year, with attendees joining both virtually and in-person, in the CTBUH Headquarters in Chicago.  
 
In this meeting, the Committee discussed the classification and criteria for composite structural materials in tall buildings. Key points included the need for clear terminology, such as differentiating between composite and hybrid structures, and the importance of structural participation. The group debated whether to set a minimum share or amount of materials for classification, considering factors like global warming potential and fire protection. They also discussed the challenges of data availability and the potential for modular and prefabricated construction to influence classification. Future topics like occupiable space measurement and construction process classification were proposed for further discussion. 

Discussion covered the origins of composite materials within construction and the importance of maintaining clear, consistent data within the CTBUH database. The group agreed that materials must be integral to the overall structure—such as a steel brace in a timber system—to qualify as composite. 

The conversation also explored how to document the rise of composite trends in current data and acknowledged the challenges of comparing global projects due to varying building codes. Limited access to detailed construction data remains a barrier, often relying on images or drawings provided by compliant firms. Existing CTBUH data could help forecast metrics like Global Warming Potential.

The group distinguished between the terms "composite" and "hybrid," noting that while composites often relate to structural efficiency, the broader concept of hybrid systems may require clearer standards as new materials emerge. The committee also addressed the complexity of classifying structural materials and the differences between precast and cast-in-place concrete, particularly regarding construction practices and modularity. 

The next Committee meeting will be taking place at the CTBUH 2025 International Conference, taking place 6-9 October 2025 in Toronto.