ᐅ Advantages and Disadvantages of Ventilation and Exhaust Systems

@DNL

...we can only manage that in the bathroom if more than one person showers one after the other!

And this moisture goes away again through consistent ventilation...

We live in an old converted calf barn, so the insulation conditions are rather poor.

Stuffy air and mold are not directly related.

Damp or moldy walls occur as follows:

There is a high absolute humidity inside. Due to missing insulation or other thermal bridges, lower temperatures occur on the wall or window surfaces (below the dew point, which can be calculated). Water vapor then condenses on these surfaces, making the wall damp and eventually causing mold. This can also happen in window reveals if the window is left tilted open for extended periods.

For this reason, many window manufacturers, for example, say that windows in older buildings shouldn’t have a too good U-value, as otherwise mold may develop. However, this is not due to the U-value itself, but because the old window was effectively ventilated by default. With the new, airtight windows, moisture condenses on the window instead of the wall.

Mold formation therefore depends not only on ventilation but also on heating. This becomes especially critical in new buildings. A solid new build typically takes around two years to dry out the moisture introduced during construction. If heating is done improperly during this time, problems can develop quickly.

And what about the correct heating behavior?

I’m familiar with opening the window for ventilation here in our rental apartment as well, built in 2000, with 17.5 cm (7 inches) calcium silicate brick and about 18 cm (7 inches) insulation.

I just hope it will be better with only aerated concrete without insulation.

winnetou78 schrieb:
I just hope that with aerated concrete alone, without insulation, it will be better.

The material itself doesn’t make a difference. A house built with aerated concrete is just as airtight, and the walls provide the same thermal insulation. By the way, with aerated concrete and generally in monolithic construction, you are more likely to encounter thermal bridges, especially around window connections and ceilings.

Better to have damp windows than damp walls. However, both problems are caused only by incorrect ventilation and ideas like "I don’t heat my bedroom and have to keep the window open at night."

...Moisture problems only occur due to incorrect ventilation habits, insufficient heating, or construction defects!

I have never experienced so much water accumulating in a heated and well-insulated house that it needs to be drained away.

This phenomenon happens when, for cost reasons, the living space is allowed to cool down during the day in the heating season, and the heating is only turned up briefly in the evening.

The wall and interior glazing then become too cold, causing water to condense on them instead of being absorbed by the warm air and removed through ventilation.

This can be easily detected with a laser thermometer...

It is important that the bathroom is vented to the outside and not into the adjacent living space!

So here in the rental apartment, the heating is definitely not set too low.
And still, everything is damp in the mornings during winter.