Glas Trösch has announced the successful completion of a pilot project on recycling old windows in Switzerland, demonstrating the technical feasibility of returning insulating glass units (IGUs) to flat glass production.
The “Windows of Opportunities” project was launched in mid-2025 under the leadership of the Zurich University of Applied Sciences (ZHAW), with participation from Glas Trösch and other partners. In the city of Winterthur, 375 window sashes were dismantled from a residential building. They were then transported to a Glas Trösch facility, where installers separated the insulating glass units from the PVC frames. The frames were also sent for recycling.
The glass was crushed, cleaned and tested for purity. This parameter is critical for reuse in float glass production. As a result, more than 2.6 tonnes of recycled glass were returned to the melting furnace at one of the Glas Trösch Group’s plants. This made it possible to reduce emissions by 1.33 tonnes of CO₂ equivalent.
For the first time in Switzerland, the project participants documented the full post-consumer IGU recycling cycle — from dismantling to remelting. Practical experience showed that all stages — dismantling, storage, glass sorting, frame recycling and cleaning — can be implemented under existing conditions. At the same time, a significant share of operations was carried out manually, increasing time consumption and highlighting the potential for further process optimisation.
Michelle Schneider, project manager and researcher at the Institute of Constructive Design at ZHAW, noted that flat glass recycling is only beginning to develop, making it important to demonstrate the practical feasibility of this approach even with additional effort. Lars Zimmerli, member of the management board of the Glas Trösch Group, added that the experience gained helps better assess how to organise the recycling process not only technically and logistically, but also economically.
Around 500,000 tonnes of window glass waste are generated annually in Switzerland. Previously, most of this volume was landfilled or used as lower-grade raw material, for example in the production of containers or insulating materials. The pilot project demonstrated that, with proper organisation, IGUs can be returned to the production of new flat glass.
The experience also confirmed the importance of careful dismantling: the integrity of the glass directly affects its potential for reuse. Particular attention was paid to logistics, storage and the prevention of material contamination. After dismantling, the PVC frames were processed into granulate and used to manufacture new profiles.
Similar initiatives are also emerging in other European countries. For example, in Denmark, VELUX has joined a project on the circular use of insulating glass units.
In Ukraine, the situation with window recycling remains challenging. The non-governmental organisation “Ukraine Without Waste” notes that disposal is still more economically attractive than sorting. There is no established system in the country for collecting and recycling old uPVC windows and doors. The lack of legislative incentives and economic motivation hampers the development of this sector, although demand for material reuse is gradually increasing.