Advances in window technology since the 1970s, such as double glazing, have significantly improved thermal efficiency. While these advances are beneficial for the energy balance, they exacerbate the problem of construction waste when windows are replaced. Today's windows are installed for an average of 30 years before they are disposed of with a glass recycling rate of only around 20%. Together with Tobias Metzger, carpenter and expert in the removal of building materials, we are researching a solution to reduce window waste. Our innovative approach focuses on the reuse of standardized double-glazed window sashes, which are converted into new, fixed-glazed windows according to current energy standards.