According to a report by the "Verband der Fenster- und Fassadenhesteller e.V." (Association of Window and Facade Manufacturers) (VFF)", you should however pay attention to carrying out the renovation measures in the correct order. The VFF therefore recommends that the windows and the building shell are updated first and the heating is then only replaced afterwards. The order of the modernization measures is so important because many house owners do not take into account that the house’s heating requirement is considerably reduced by new windows and improved external insulation and that the new heating system may end up being smaller and cheaper.
So it's worth investing in new windows. Because our modern insulating windows have a high insulating effect. The investment in new insulating windows can save around 500 liters of oil per year, depending on the window area. Up to EUR 400 can be saved depending on the window area.
Döpfner windows are on the cutting edge of technology and have the best insulation properties. See for yourself.