Insulated glass units (IGUs) are essential components of contemporary energy-efficient building envelopes. The most conventional edge seal design in an IGU is the dual-sealed metal spacer. Although float glass is highly durable and recyclable, the service life of an IGU is limited to 20 - 30 years due to the degradation of sealants. UV exposure, thermal cycling, moisture ingress and mechanical stresses can compromise the durability leading to gas leakage, condensation within the cavity and reduced thermal performance. Furthermore, the permanent adhesion between glass panes, sealants and spacer prevents clean disassembly and often leads to contamination of glass cullet during recycling processes. As a result, most end-of-life IGUs are downcycled, mechanically crushed or disposed of as mixed construction waste rather than being reused or recycled into high-quality applications. Existing industry innovations have predominantly focused on improving thermal performance through warm-edge technologies, while the challenges of durability and circularity remain largely unresolved.
This research address the gap between thermal performance optimisation and the need for edge seal systems that simultaneously extend service life and support circular design strategies. Therefore, the objective of this master’s thesis is to redesign the edge seal component of insulated glass units (IGUs) through material innovation and research-informeddesign, to enhance durability and enable circularity, while maintaining the required performance of IGUs and ensuring compatibility with standard façade systems.
Through literature-based exploration and systematic evaluation of the current-state-of the-art and its limitations and by looking into the requirements and regulations according to the literature and the NEN norms and standards, a list of design criteria, to which a redesign of the IGU edge seal component should comply, was formed. These criteria included thermal, mechanical, moisture and gas resistance requirements, as well as additional criteria related to durability, demountability, contamination, and circularity. The analyses demonstrate that the spacer and sealant components require fundamentally different material properties and therefore cannot be effectively replaced by a single material category. Material screening using the Granta EduPack database software combined with technical innovative literature-based connection research demonstrated that the most promising redesign strategy for the IGU edge seal system consists of combining a heat-bonded glass spacer connection with a flexible and preferably thermally debondable polymer-based sealant system. Experimental investigations demonstrated that glass fusion can create a durable and contamination-free connection. In addition, a thermally debondable connection using PETG showed potential as a reversible sealing strategy.
The resulting hybrid edge seal concept was evaluated against predefined design criteria. The results indicate that the concept can provide high thermal insulation, mechanical stability, environmental resistance, and air- and watertightness while significantly improving circularity. By limiting contamination to a single removable side and enabling future disassembly, the design facilitates reuse, remanufacturing, and high-quality recycling of glass panes. Furthermore, the replacement of conventional metal spacers reduces thermal bridging and contributes to improved thermal performance. Although the concept remains at a proof-of-concept stage and requires further validation through accelerated ageing, durability testing, and full-scale prototyping, the findings demonstrate the potential of redesigning the IGU edge seal as a strategy to simultaneously improve durability and circularity. The research contributes to the growing field of circular façade design by shifting the focus from end-of-life management towards design-level interventions that address the root causes of premature IGU replacement. Demonstrating how material innovation and research informed design can support the development of durable and more circular glazing  systems.  ... Read more