Studies on the Recycling and Reuse of Used Glass Panels

Across Germany, 209 million window units are in need of renovation due to building physics limitations. Typically, the resulting waste glass panels are recycled and supplied as glass cullet to the container glass industry. As a result, high-quality raw materials are lost to the flat glass industry.

To enable the use of used glass panes in line with the principles of circular construction and the circular economy, the Chair of Structural Engineering at the University of Siegen is conducting conceptual and experimental studies on the reuse and recycling of used glass panes. In collaboration with regional partners, renovation projects are identified and removed glazing is secured. In the chair’s own testing facility, single-pane and multi-pane insulating glass units are tested for their performance. Non-destructive testing methods are available for this purpose, such as cross-sectional analysis, measurement of radiative and photometric properties, and determination of the U-value (Ug). Destructive methods, such as measuring the gas fill level, separation of the used glass panes from the spacer of the edge seal in multi-pane insulating glass, and the subsequent testing of the used glass’s strength in double-ring bending tests and four-point bending-tensile tests, provide empirical data and statistical insights into the remaining mechanical performance.

The goal of the investigations is to evaluate the suitability of used glass panes for reuse and to create resource-efficient and circular solutions in glass and facade construction. This research develops evaluation criteria for the safe and needs-based reuse of used glass panels.