Puddles through cold bridges
That about 25 year old house, what we bought now, is equipped with brown anodized aluminum windows . They are in perfect condition and close 100%. However, it is getting colder outside, sweat profusely, small puddles forming on the window sill. What can you do about it?
The windows in your house are probably first-generation aluminum windows. Die Profile, from which the windows were assembled, were pressed in one piece and therefore only had one chamber.
This created a cold bridge. When the outside temperature is low, these window frames conduct the cold inwards, the warm inner air cools down considerably on the metal surface. This reduces the water storage capacity of the room air and the released moisture condenses on the frame. The formation of condensate can be avoided by regular and intensive ventilation. This keeps the humidity in the room as low as possible. Today the metal window profiles have at least two chambers, connected to each other only by insulating plastic bars (thermally separated) are. The chambers are filled with insulating foam. Unfortunately it is not possible, to retrofit old windows accordingly.