Dispelling a myth: Condensation
We face a problem that involves many people: Condensation.
Which are the causes?
In winter, heated environments have an excessive vapor content (produced by activities such as sleeping, cooking, showering or with normal household activities) than outside, this pressure difference produce the migration of the vapor from the inside to outside through the walls. That’s why the temperatures of the interior walls must stand above the so-called dew point to prevent condensation on the walls and then mold on the surfaces.
If the wall is a little isolated, or there are thermal bridges (for example, a pillar of reinforced concrete), and the surface temperature of the walls falls below a certain value, here is that the development of condensation is guaranteed.
The old windows didn’t heat up the environment for their low resistance, but thanks to the drafts ensured a slow but steady replacement of indoor air and a humidity disposal of the house, which now no longer takes place. The new windows indeed block the drafts, thus causing an increase of the degree of interior humidity.
A simple relief for this unpleasant phenomenon is the proper ventilation of the premises.
Changing the air in closed environments is very important.
If we do not it the humidity that we produce – cooking, washing or simply breathing – accumulates and facilitates the appearance of mold on the walls. Even the concentration of polluting substances tends to increase, for example carbon monoxide generated by the incomplete combustion of gas ring or formaldehyde released by some building materials.
So, in default of a mechanical ventilation system, it is recommended to open the windows about every two hours (in the residential environment occupied by people).
How long the window must remain open? It depends on several factors:
• casement or turn and tilt opening
• season, because in winter the temperature difference between inside and outside speeds the recirculation
• presence of wind, which favors the replacement
• air flow in the room, which speeds up the circulation.
The diagram below (source: IBN – Institut Für Baubiologie + Ökologie Neubeuern) summarizes the opening times.
Casement opening with air flow. Winter: 2 – 4 mins. Summer: 12 – 20 mins.
Turn and tilt opening with air flow. Winter: 4 – 6 mins. Summer: 25– 30 mins.
Casement opening without air flow. Winter: 4 – 6 mins. Summer: 25 – 30 mins.
Turn and tilt opening without air flow. Winter: 30 – 75 mins. Summer: 3 – 6 hours.