Windows are important elements in a building. They protect the interior from the exterior environment regarding weather conditions, noise, security and so on. While they also, in contrast to walls and floors, connect the two, creating links and providing rooms with daylight, fresh air and views in and out of the building. The most governing element of the window is the insulated glazing unit (IGU). There are many developments concerning coatings to add functions to the glass ,such as solar control or self-cleaning windows but they contain critical materials such as cobalt, copper and titaninum. Added elements such as coatings, foils for laminated glass and the sealant prohibit the IGU from being recyclable, as the prevailing glass industry requires high quality and clean ingredients only. This makes the IGU a finite, single life product resulting in almost 125.000 tonnes of post-consumer glass waste each year in the Netherlands. The IGU works optimally as an insulating element as long as there is dry (argon) gas inside the glazing panes. However, the life span of current IGUs is just around 15-20 years and is dependent on the butyl seal which is just 1% of the costs and 0.1% of the weight. During its life span the seal starts failing by allowing water molecules inside the cavity. The panel as a result starts building up water vapor and the coating inside will start to corrode, the glass shows fogging and the thermal performance drops down due to outgassing of the panel. In the current design of the IGU no refurbishment is possible, meaning that the glass panes and the spacer will not be re-used, but instead end up as landfill while these materials exceed the life span of the sealant by a large margin (Veer,2016). This thesis therefore focusses on the possibility of remanufacturing the IGU. The re-designed edge seal system for the IGU makes it easy to remanufacture the IGU on-site. The design utilises a detachable butyl seal that functions as a dry gas and vapor barrier and a hollows section that assures the tightness of the seal. This idea shows the possibility to replace the weakest part of the whole glazing panel every ten years so that the glazing panes which have high stored embodied energy and the spacer bar, which is currently approaching the theoretical value in terms of energy efficiency, both can have a life span of more than 100 years. The interlocking design of the spacer bar and butyl sealant is a result of a form finding process. A fiberglass hollow section can be slid into the butyl profile to assure the load is transfered to the window system. Furthermore, a check valve type is chosen to fill the cavity again with Argon gas with every remanufacturing cycle.

The ambition of the Netherlands is to have a fully circular economy by 2050. One of the steps to achieve this ambition is that in 2030 the tenders should have circular ambitions at all governmental levels. However, at the moment, there are insufficient tools for the municipality to make the practical implications of these circular ambitions explicit. In a studied case-project in Reigersbos (Amsterdam), where circular facades are being applied, a selection procedure has taken place to unify different parties that are willing and able to enhance the circularity of the project. Such a tender process is complex and time-consuming. A tool that streamlines circular requirements can help the selection procedure for the parties involved early in the process and can actively keep track of realisation of the set requirements during the process. Therefore, the thesis aims to develop a circular tendering tool that actively helps the municipality and project developer set circular ambitions and criteria for an arbitrary project location. The tool’s concept is to categorize and assess the individual benefits of the circular measures in the chosen products, phases and parties, based on the principle of the circular economy. By utilizing this tool, it becomes possible to compare and select a facade system for the project. Furthermore, it also keeps track of the process by monitoring the set goals during the project for necessary adjustments and allows evaluating of the goals in the end.