Insulate aluminum windows - is that possible?

With old aluminum windows you can often clearly feel how the cold penetrates from the outside to the inside. If you can isolate such old windows, you can see what options are offered, and what works better, you can read here.

Problems with aluminum windows

Old aluminum windows - even if they are not that old - are fundamentally different in structure from today. Especially in metal windows, the design has changed significantly in recent years. The most important point concerns the thermal separation.

Thermic separation

Old aluminum windows are set in continuous aluminum frames. These continuous frames have no thermal separation from outside to inside.

Since aluminum is a good conductor of heat, the cold on the outside is absorbed by the aluminum and radiated inwards. This works like a cooling radiator in terms of building physics. The cold gets over the windows directly into the interior.

New aluminum windows are designed so that the inner part of the frame with the outer part is not in direct heat-conducting connection. As a result, this phenomenon does not occur in modern windows.


Due to the cold air emitted by the window, the warm indoor air can suddenly cool down on the inside. It then condenses and condensation forms on the inside of the frame.

This brings a lot of moisture into the living room, as more and more warm air flows to the window, and there also condenses again. The result may be moisture damage to the wall due to dripping condensate.

Condensation in the window

Another problem with old windows is the spacer. This is usually made of aluminum and is associated with the winter cooled frame. This leads to a massive cooling of the glass edge, the so-called edge bond. The inner glass pane is warm, however. This can also form condensate, which then runs into the window frame.


In many cases, a "foaming" is tried with Ortschaum to prevent the refrigerant line from the outside to the inside. Due to the design of old window frames, this method is not effective and in most cases not at all possible.

The basic problem, namely the design of the window frame is not resolved. The only reasonable remedy is an exchange of windows. Considering the very high U-value of old metal windows, a replacement by the savings in heating costs amortizes relatively quickly. In addition, the living climate improves significantly in winter.

Tips & Tricks

You can calculate the amortization period for the windows if you use one of the numerous online computers. In the case of old aluminum windows, you can still clearly give savings to the result, since the problem in this case is not only the glazing but, above all, the frame.

Video Board: insulbar (EN): How to insulate aluminium windows using thermal separation