We face a problem that involves many people: Condensation.

What are the causes?

In winter, heated rooms have an excessive vapor content (produced by activities such as sleeping, cooking, showering or with normal household activities) compared to the outside, this pressure difference causes the migration of steam from inside to outside through the walls. This is why the temperatures of the internal walls must stay above the so-called dew point to avoid condensation on the walls and therefore mold on the surfaces.

If a wall is poorly insulated , or there are thermal bridges (for example a reinforced concrete pillar), and the surface temperature of the walls drops below a certain value, condensation is guaranteed.
The old windows made people stay cold due to their poor sealing, but thanks to the drafts they ensured a slow but constant exchange of the internal air and a disposal of the humidity of the house, which now no longer happens. The new windows in fact they block drafts, thus causing an increase in the degree of internal humidity .

A simple remedy to this unpleasant phenomenon consists in the correct ventilation of the premises .

Replacing the air indoors is very important.
If we do not do this, the humidity we produce – by cooking, washing or simply breathing – accumulates and facilitates the appearance of mold on the walls. The concentration of pollutants also tends to increase, for example the carbon monoxide generated by the incomplete combustion of gas stoves or the formaldehyde released from some building materials.

Therefore, in the absence of a mechanical ventilation system, it is advisable to open the windows about every two hours (in residential areas occupied by people).

How long should the window stay open? It depends on several factors:
• hinged or flap opening
• season, because in winter the difference in temperature between inside and outside speeds up recirculation
• presence of wind, which favors the turnover
• air flow in the room, which accelerates the recirculation.

The drawing below (source: IBN – Institut Für Baubiologie + Ökologie Neubeuern) summarizes the opening times.