Condensation

What is condensation

Condensation is a physical process by which the gaseous water reaches a liquid state or goes from liquid state to solid state. Condensation usually occurs in winter due to the structure of the building that contains thermal bridges as well as inefficient ventilation. Then the moisture in the air persists.

Reaching the dew point

The dew point occurs when the air, with a certain temperature and humidity, can no longer absorb an additional amount of water vapor. Air in an enclosure with a temperature of 20 degrees celsius and a relative humidity of 50% can absorb another half of the maximum possible amount

If there is air cooling at 9.3 degrees Centigrade, the relative humidity will increase to 100%. The air is so saturated with steam and reaches the dew point. Cooling above this level (9.3 degrees C) will result in condensation, because air can no longer absorb water. The 20 degrees Celsius temperature, saturated with 17.3 grams of vapor / m³, by cooling to 10 degrees celsius (the maximum absorbed quantity being 9.4 g of vapors / mc), gives rise to 7.9 g of condensed water / mc.

Apparently all modern windows look the same

In spite of the new joinery / facades wall systems and substantial investments, many beneficiaries accuse problems of condensation in the cold season. The analysis of this phenomenon involves the identification of the causes: design, execution, assembly, exploitation, maintenance, etc. The lack of competence in choosing the system at the design stage, renders the beneficiary’s effort in avoiding the condensation as unnecessary. Incorrect execution, improper installation, complemented by inappropriate exploitation, represent the full range of phenomena commonly found on the market. The presence of just one of the previously mentioned causes is sufficient for the condensation to occur. On the domestic market are still in operation a lot of windows and facades made with aluminum profiles or steel without thermal barrier.

The cold season scares many of the beneficiaries because of the discomfort, moisture and mold fungus generated by the leakage of industrial amounts of water on the windows and walls. This situation is also encountered in a series of newly installed windows. Apparently all windows look the same, they are characterized by attractive design, wide range of shapes and colors, but the performances remain at the disposal of manufacturer.

Condensation may appear on the surface or inside a wall.

To answer the condensation questions, we must mention that the modern windows provide a very good seal, which helps to eliminate energy waste. The rain, the wind, the cold do not enter the room anymore, and thus the exchange between the interior and the exterior is not done naturally, but it occurs ionly through periodic ventilation. The air contains different amounts of water vapor. For comfort and health reasons, relative humidity at room temperature should be between 40% and 60%. When the air humidity reaches more than 60%, the air can no longer keep the water vapor, and it condenses on the coldest surface, which in the room is usually the glass or the wall. The old, wooden windows, which were not sealed, ensured forced ventilation, thus solving the problem of humidity and condensation.

Factors that favor condensation are: unaired rooms, unheated rooms, thick curtains in front of the windows, non-diffusive walls, building humidity in new constructions, existence of vapor generating sources, the presence of ornamental plants in the rooms and their location in the vicinity of the windows, inappropriate heating and glazing sources.

Where does the moisture come from in a building?

Condensation can occur on the inner surface of the double pane glass, respectively of the frames. This is also the case for the formation of exudate water or condensation water. This phenomenon should not be confused with the condensation in the intermediate space of the double pane glass, which is a very rare case of execution defect. Causes of condensation water on the insulating glass, or on window frames, are explained below.

There are permanent water vapors in the house:

  1. In human-breathing air: the daily amount of 1-2 liters;
  2. From cooking: up to 2 liters in a household of 4 people;
  3. Household activities (bathroom, laundry, flower watery) bring up to 3 liters in a 4-person household.

These quantities are permanently found as water vapor, invisible in the air. Thus, one cubic meter of air at 0 ° C can contain a maximum of 5g (representing 5 cm3) of water vapor. If the room temperature increases, then the air can get a larger amount of water. So at 20oC we will have 17g and at 30oC it will reach 30g per m3.

If the maximum amount of water vapor is contained in the air, then the air no longer receives moisture in the form of water vapor and becomes saturated air with a relative air humidity of 100%. For example, consider a space of 15m2 in area and 2.5m in height with a volume of about 38m3. If the air has a temperature of 23 ° C, it floats in this space, at 100% humidity, almost 1 liter of water in the form of invisible vapors results.

If during night the room temperature drops a few degrees, then some of the water vapor in the air condenses on the existing cold surfaces: windows or profiles. Condensation also occurs when the room air humidity is high, and the surface temperature on the inside of the window is low. Condensation always starts at the edge of the glass where there may be areas that are not properly sealed. The circulation of the hot air that "touches" the glass can be limited by a too large window case over the radiator which leads to the appearance of condensation at the bottom of the window. In less heated rooms condensation may occur on cold days and on windows with insulating glass. This is due to the fact that the space is saturated with water vapors produced by breathing during the night at a low temperature. In addition, we specify that the formation of condensation water can occur not only on windows or window frames but also on all cold surfaces what finally leads to moisture and mold formation on the walls.

Other situations that may lead to condensation:

  1. If the humidity in the room is high and the inside temperature of the insulating glass is low;
  2. If the hot air cannot circulate from the heating elements to the window
  3. If the rooms are not sufficiently ventilated (considering that this type of joinery is sealed, unlike classic carpentry and does not allow the spontaneous exchange of air);
  4. If the windows are mounted in the outer half of the wall (cold area);
  5. If it is not sealing properly on the contour.
  6. Existence of vapors generating sources: domestic activities, bathroom, kitchen etc; Daily food preparation (use of stove);
  7. Creating additional vapors by breathing causes an increase in humidity, resulting in condensation, especially during the cold season;
  8. Presence of natural plants, inappropriate location;
  9. Obstructing air circulation through curtains or blinds is another factor contributing to condensation.

Condensation can be prevented by following certain rules:

  1. Using (quality) PVC profiles with 3-5 air chambers;
  2. The use of low-emissivity (LOW E) and argon heat-insulating glass panels, which decreases the heat loss by 50% compared to the regular heat-insulating glass;
  3. A low emissivity (LOW E) insulating glass, at -10 ° C in the exterior and + 20 ° C in the interior, has a temperature + 17 ° C on the interior glass compared to an ordinary insulating glass which, under the same conditions, has a temperature of only +9 oC
  4. Installation of the windows from the middle of the wall towards the inside (in the hot zone);
  5. Robust sealing of the carpentry on the contour of the frames both inside and outside;
  6. Frequent ventilation of these spaces as modern PVC or aluminum carpentry stops air transfer.

Household users who have new double pane glasses should take into account the adaptation to new ventilation conditions. The old windows were usually unsealed and allowed a permanent exchange of air. In the case of new, more airtight, double pane glasses, the uncontrolled exchange of air is no longer possible, so residents need to provide room ventilation to avoid condensation (ventilation must be done at least 2-3 times a day)

The rooms that are located in the northern part of the houses are colder in the winter. Take care that these rooms are better heated than the southern ones or supplement their thermal insulation. Also the temperatures in your home do not differ from one room to another. In the morning, it is recommended to air the spaces for about 20 minutes and after opening the windows, the heating should be uniform and at moderate temperatures

You can reduce the risk of condensation by:

  1. Proper ventilation, followed by uniform heating at moderate temperatures;
  2. Modifying the hot air circulation so that the hot air flow passes along the window to obtain higher heat transmission coefficients;
  3. Where there is interior glazing covering the radiant surfaces of the heating bodies, you should drill holes in the glazing to allow the hot air circulation to the windows;
  4. Rooms oriented north, or in the direction of the dominant wind, should be better heated and isolated

IMPORTANT: Condensation is an absolutely normal phenomenon whose appearance does not necessarily lead to the idea that PVC joinery is not well executed! A good ventilation of the room as well as the use of Low-e glass will improve the effects of this unpleasant phenomenon.

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