Condensation is a process where the physical state of the water vapour contained in the air changes from the gas into drops of water appearing on the surfaces that are in touch with the air. Normally the air has particular humidity which means it includes some quantities of the water vapour. When the conditions change - either the temperature goes down or the humidity goes up or both of the conditions change - this leads into the condensation.


The drops appear. In the buildings there is a matter of where the dew point is located - the point in which the temperature, air humidity and its pressure enable water vapour condensation. In order to dislocate the dew point out of the building area it is highly recommended to lift up the temperature in the building or/ and to prevent the increase of the humidity by sufficient ventilation. It is very essential especially in the new buildings that have been closed (doors & windows) but where still finishing works are being performed (wet technology like concrete, mortar, paint etc).

Seasons such as autumn, winter, spring decrease a building air temperature in a natural way, what enhances the risk of condensation appearance. In critical situations it is highly recommended not only to increase the temperature of an inside but also to intensify the ventilation through open windows and doors, what unfortunately generates significant
heating costs.

Therefore, it is recommended to conduct finishing works in closed buildings during warm seasons, when air temperature counteracts the condensation in a natural way. In such conditions opening windows and doors in a building increases air ventilation, continues evaporation of humidity contained in construction substrates while drying them with out the need of artificial temperature rising of an inside.

Moreover, in case of a roof and an attic, independently on the above mentioned factors, proper choice and installation of waterproofing and ventilating materials has to be assured in order to ensure right tightness and ventilation in the building as well as good and effective functionality , far from condensation problem. Membranes and roof foils, ventilating and protecting elements of a ridge, eaves can be applied here and various, professional sealing tapes for each of the areas.


  • Avoid carrying out wet works in a building in the winter season
  • Pay attention at proper ventilation performance in a building, especially in case of renovated and converted rooms.

See also

Environmental Product Declaration

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Changes to the Eurovent® packaging line

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UV resistance

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Temperature resistance

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Wind barrier membranes

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Vapour difusional resistance (Sd)

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