Water vapour – “sweating” on aluminium systems (frames)

Many people wonder why their windows sweat, (liquefaction in the windows).The phenomenon of liquefaction of water vapor occurs when in a closed space there is a high concentration of water vapor in the air (eg kitchens, bathrooms) and at the same time within this space there are cold surfaces on which water vapor is liquefied.

In all frames (aluminium, wood, Pvc) the phenomenon of liquefaction of water vapour in the atmospheric air occurs in the winter months, where the low outdoor temperature keeps the frames frozen, while at the same time the high temperature of the indoor space allows the increase of the concentration of water vapour in the air.In aluminium energy frames, liquefaction occurs on a much smaller scale in the glazing due to the high thermal resistance. In combination with the high waterproofing of aluminium frames, the trapped air with the increased concentration of water vapour is liquefied on all cold surfaces, so we see on the frames of aluminium frames or on the glazing (liquefaction on the glazing) drops of moisture forming.

Indoor humidity (easily measured with a hygrometer) increases with cooking (this is why the phenomenon is more pronounced in kitchens and bathrooms), intense physical exercise, the steam of a hot bath and in newly built houses mainly due to the recent application of coatings. The liquefaction always starts at the edge of the glass and even at the bottom of the window. This is because the construction of windows is thermodynamically ‘asymptotic’. The hot air stream cannot come into contact with the whole glass, there is a blind spot, the area of which is the last to be heated. Humidity occurs in rooms that are not sufficiently heated, especially at night (bedrooms). While the temperature of these rooms usually drops at night, the percentage of humidity rises due to exhalation. It should be noted that liquefaction occurs not only on glass and frames (wood, PVC, aluminium) but also on all cold surfaces of a room. This leads to the formation of stains and mould on cold (usually north-facing) walls.

But basically, by using some simple rules, the phenomenon can be reduced or even eliminated. The most basic rule for avoiding moisture (in frames and walls) is adequate ventilation of the rooms. However, this should not be done by continuous ventilation (increasing energy consumption) but by momentary ventilation, i.e. opening a window for 5-10 minutes, so that the humidity-saturated air in the room is replaced by cooler but drier air from outside.
After 5-10 min we close the window again , turn on the heating so that we heat the cold air which at higher temperatures can now also absorb more moisture in the room. After 3-4 hours the air has absorbed the moisture and the same process can be repeated from the beginning.

  • Heating shutdown
  • Opening the window (for 5-10 min)
  • Closing the frame
  • Heating opening

The whole procedure is repeated 3-4 times a day. The above procedure should be followed mainly by owners of old apartments – houses that have recently replaced the frames.
This is because old houses do not have the insulation of modern ones and as a result the temperature difference between the wall and the interior is greater and as a result the air cannot absorb more moisture and therefore more moisture is left over and settles on any cold surface. The new frames are hermetically sealed so that they do not allow the exchange of outside air with the inside air.

Suggested solutions to deal with liquefaction in glazing

The first thing you should do if your windows or windows are dripping water is to get a hygrometer (available at home improvement stores and costs very little) and measure the humidity inside your home. If the humidity level is over 65% – 70% then there is a problem. The installation of new energy efficient aluminium frames is a solution . However, it is not certain that the problem will be solved permanently in cases where the humidity inside the house is above 80% . If the problem is not solved permanently, which is rare, the source of the humidity should be sought and the contribution of a civil engineer may be needed. Some general guidelines for dealing with the problem of dripping windows, balcony doors or windows . It is the adequate ventilation of the room by opening the windows in the morning hours, so that the remaining moisture can escape. As well as the use of dehumidifiers or air conditioners in Dry mode.

Under no circumstances should we overlook the problem and remain exposed to such moisture levels. Because it is a very aggravating factor for our health and the health of our family.

– We make sure that the room is adequately ventilated so that the concentration of humidity remains low.
– We use a dehumidifier or air conditioner in dry mode from time to time.

It should be noted that the phenomenon of liquefaction in the glazing can occur in aluminum energy frames but in more extreme weather conditions compared to conventional frames and in all types of frames (PVC, wood) if the prevailing humidity is above 60%.